View EVAL-ADE7763EB_3044392.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

single-phase active and apparent energy metering ic ade7763 rev. a in fo rmation furn ished by an alog d e v i c e s is believed to be accurate and reliable. how e ver, n o resp on sibili ty is assume d b y a n alog de vices fo r its use, nor for an y i n fri n geme nt s of p a t e nt s or ot h e r ri ght s o f th ird parties th at may result fro m its use . specifications subjec t to chan g e witho u t n o tice. no licen s e is g r an te d by implicati o n or ot herwi s e u n der a n y p a t e nt or p a t e nt ri ghts of analog de v i ces. trademarks an d registered tra d ema r ks are the prop erty o f their respective ow ners. one technolog y way, p.o . box 9106, norwood, ma 02062-9106, u.s.a. t e l: 781. 329. 4 700 www.analog.com fax: 781. 326. 87 03 ? 2004 analog de vices, i n c. al l r i ght s r e ser v ed . fea t ures high accuracy; supports iec 6 1036/606 87, ie c62053 -21, an d iec62053 -22 on-chip digital integrator ena b les direct inte rface-to-curren t sensors with di /dt output a pga in the current channel a llows direct int e rface to shunts and cur r ent transformers active an d app a rent energy, s a mpled wa vef o rm, and curre nt and voltage rm s less than 0.1% error in active energy meas ur ement over a dynamic range of 1000 to 1 at 25c positive-only e n ergy accumul a tion mode available on-chip user programmable threshold for lin e voltage s u rg e and sag and p s u super v isory digital calibrat ion for power, phase, and inp u t offset on-chip tempe r ature sensor ( 3c typical) spi?-compatibl e serial interfac e pulse outp ut w i th programmable frequency interrupt request pin ( irq ) and st atus register reference 2.4 v with external overdri v e cap a bility single 5 v supp ly, low power ( 25 mw t y pical) gener a l de scription the ad e7763 1 fe a t ur es p r o p r i e t a r y ad cs a nd f i xe d f u n c t i on ds p f o r high accurac y o v er la r g e va r i a t io n s in en vir o nm en tal co ndi tion s an d tim e . the ad e 7763 in co r p o r a t es tw o s e cond- o r der , 16-b i t - ? ad cs , a dig i t a l in teg r a t o r (o n c h 1), r e fer e nce cir c ui t r y , a t e m p era t ur e s e ns o r , a nd al l t h e sig n al p r o c es sin g r e q u i r ed t o pe rf o r m a c ti v e a n d a p pa r e n t en e r g y m e as u r e m e n ts , line-vol t a ge p e r i o d m e a s ur eme n ts, and r m s ca l c u l a t ion o n t h e v o l t a g e an d c u r r en t c h a n ne ls. th e s e le c t a b le on-c hi p dig i tal in teg r a t o r p r o v i d es dir e c t i n t e r f ace t o di/ d t c u r r en t s e n s o r s such as rogo wsk i co i l s, e l im ina t in g t h e n e e d fo r a n e x t e r n a l a n a l og in teg r a t o r an d resu l t in g in exc e l l en t lo n g - t er m st a b i l i t y a nd p r e c is e phas e ma t c hin g b e tw e e n t h e c u r r en t and t h e v o l t a g e cha nnels. the ad e7763 p r o v ides a s e r i al in t e r f ac e t o r e ad da ta and a pu l s e output f r e q u e nc y ( c f ) t h a t i s prop or t i on a l to t h e a c t i v e p o w e r . v a r i o u s sy stem c a lib r a t i o n fe a t ur es such as cha nnel o f fs et co r r ec tio n , p h as e cal i b r a t io n, an d p o w e r cal i b r a t io n en s u r e hi g h acc u rac y . th e p a r t als o det e c t s sh or t d u ra t i o n , lo w or h i g h vo lt age v a r i at i o ns . t h e posi ti v e - o nl y a c cum u la ti o n m o d e gi v e s t h e o p ti o n t o a c cum u l a t e en er g y o n l y wh e n pos i ti v e p o w e r i s d e t e c t ed . an in t e r n al n o -lo a d thr e sh old e n sur e s tha t t h e p a r t do es n o t exhib i t a n y cr e e p w h e n t h er e is n o lo ad . the zer o -cr o s s in g o u t p u t (z x) p r o d uces a p u ls e t h a t is sy n c hr o n ize d t o t h e ze r o -cr o s s in g p o in t o f th e l i ne v o l t ag e . this sig n a l is us ed in t e r n al ly in t h e line c y c l e ac t i ve and a p p a r e n t e n erg y acc u m u l a t i o n mo d e s, w h ich ena b l e s fas t er calib r a t io n. the i n ter r up t st a t us r e g i ster i n di c a tes t h e na t u r e o f t h e i n t e r r upt, a n d t h e in t e rr u p t e n a b l e r e gi s t er co n t r o l s wh i c h ev en t p r o d uces an output on t h e ir q p i n , a n o p en-dra in, acti v e lo w logi c o u t p u t . the ad e7763 is a v a i la b l e in a 2 0 -lead sso p p a c k a g e . func tio n a l block di agram avdd reset dvdd dgnd temp sensor adc adc dfc x 2 ade7763 lpf2 multiplier integrator clkin clkout din dout sclk ref in/out cs irq agnd apos[15:0] vagain[11:0] vadiv[7:0] irmsos[11:0] vrmsos[11:0] wgain[11:0] dt registers and serial interface cfnum[11:0] cfden[11:0] 2.4v reference 4k ? phcal[5:0] hpf1 lpf1 04481- a - 001 v1p v1n v2n v2p pga pga zx sag cf wdiv[7:0] % % x 2 fi g u r e 1 . 1 u.s. patents 5,745, 323; 5,760,617; 5, 862,069; 5,872,469; others pen d ing.
ade7763 rev. a | page 2 of 56 table of contents specifications ..................................................................................... 3 timing characteristics ..................................................................... 5 absolute maximum ratings ............................................................ 6 esd caution .................................................................................. 6 ter mi nolo g y ...................................................................................... 7 pin configuration and function descriptions ............................. 8 typical performance characteristics ........................................... 10 theory of operation ...................................................................... 13 analog inputs .............................................................................. 13 di/dt current sensor and digital integrator ........................... 14 zero-crossing detection ........................................................... 15 period measurement .................................................................. 16 power supply monitor ............................................................... 16 line voltage sag detection ....................................................... 17 peak detection ............................................................................ 17 interrupts ..................................................................................... 18 temperature measurement ....................................................... 19 analog-to-digital conversion .................................................. 19 channel 1 adc .......................................................................... 20 channel 2 adc .......................................................................... 22 phase compensation .................................................................. 24 active power calculation .......................................................... 25 energy calculation ..................................................................... 26 power offset calibration ........................................................... 28 energy-to-frequency conversion ............................................ 28 line cycle energy accumulation mode ................................. 30 positive-only accumulation mode ......................................... 30 no-load threshold .................................................................... 30 apparent power calculation ..................................................... 31 apparent energy calculation ................................................... 32 line apparent energy accumulation ...................................... 33 energies scaling .......................................................................... 34 calibrating an energy meter .................................................... 34 clkin frequency ...................................................................... 43 suspending functionality .......................................................... 44 checksum register ..................................................................... 44 serial interface ............................................................................ 44 registers ........................................................................................... 47 register descriptions ..................................................................... 50 communication register .......................................................... 50 mode register (0x09) ................................................................. 50 interrupt status register (0x0b), reset interrupt status register (0x0c), interrupt enable register (0x0a) ............... 52 ch1os register (0x0d) ............................................................ 53 outline dimensions ....................................................................... 54 ordering guide .......................................................................... 54 revision history 10/04data sheet changed from rev. 0 to rev. a changes to period measurement section ..................................16 changes to temperature measurement section........................19 change to energy-to-frequency conversion section..............28 update to figure 61 .......................................................................29 change to apparent energy calculation section .....................32 change to description of aehf and vaehf bits ...................52 4/04revision 0: initial version
ade7763 rev. a | page 3 of 56 specifications av dd = dv dd = 5 v 5%, agnd = dgnd = 0 v, on-chip reference, clkin = 3.579545 mhz xtal, t min to t max = C40c to +85c. table 1. specifications 1, 2 parameter spec unit test conditions/comments energy measurement accuracy active power measurement error clkin = 3.579545 mhz channel 1 range = 0.5 v full scale channel 2 = 300 mv rms/60 hz, gain = 2 gain = 1 0.1 % typ over a dynamic range 1000 to 1 gain = 2 0.1 % typ over a dynamic range 1000 to 1 gain = 4 0.1 % typ over a dynamic range 1000 to 1 gain = 8 0.1 % typ over a dynamic range 1000 to 1 channel 1 range = 0.25 v full scale gain = 1 0.1 % typ over a dynamic range 1000 to 1 gain = 2 0.1 % typ over a dynamic range 1000 to 1 gain = 4 0.1 % typ over a dynamic range 1000 to 1 gain = 8 0.2 % typ over a dynamic range 1000 to 1 channel 1 range = 0.125 v full scale gain = 1 0.1 % typ over a dynamic range 1000 to 1 gain = 2 0.1 % typ over a dynamic range 1000 to 1 gain = 4 0.2 % typ over a dynamic range 1000 to 1 gain = 8 0.2 % typ over a dynamic range 1000 to 1 active power measurement bandwidth 14 khz phase error 1 between channels 0.05 max line frequency = 45 hz to 65 hz, hpf on ac power supply rejection 1 avdd = dvdd = 5 v + 175 mv rms/120 hz output frequency variation (cf) 0.2 % typ cha nnel 1 = 20 mv rms, gain = 16, range = 0.5 v channel 2 = 300 mv rms/60 hz, gain = 1 dc power supply rejection 1 avdd = dvdd = 5 v 250 mv dc output frequency variation (cf) 0 .3 % typ channel 1 = 20 mv rms/60 hz, gain = 16, range = 0.5 v channel 2 = 300 mv rms/60 hz, gain = 1 irms measurement error 0.5 % typ over a dynamic range 100 to 1 irms measurement bandwidth 14 khz vrms measurement error 0.5 % typ over a dynamic range 20 to 1 vrms measurement bandwidth 140 hz analog inputs 3 see the analog inputs section maximum signal levels 0.5 v max v1p, v1n, v2n, and v2p to agnd input impedance (dc) 390 k min bandwidth 14 khz clkin/256, clkin = 3.579545 mhz gain error 1, 3 external 2.5 v reference, gain = 1 on channels 1 and 2 channel 1 range = 0.5 v full scale 4 % typ v1 = 0.5 v dc range = 0.25 v full scale 4 % typ v1 = 0.25 v dc range = 0.125 v full scale 4 % typ v1 = 0.125 v dc channel 2 4 % typ v2 = 0.5 v dc offset error 1 32 mv max gain 1 channel 1 13 mv max gain 16 32 mv max gain 1 channel 2 13 mv max gain 16
ade7763 r e v. a | pa ge 4 o f 5 6 p a r a m e t e r s p e c u n i t t e s t condition s / c o m m e n t s waveform s a mpling sampling clkin / 128, 3.579545 mhz/128 = 27.9 ksps channe l 1 see the channel 1 sampling sect ion signal-to-noise plus distortion 62 db typ 150 mv rms/60 hz, range = 0.5 v, gain = 2 bandwidth (C3 db) 14 khz clkin = 3.57954 5 mhz channe l 2 see the channel 2 sampling sect ion signal-to-noise plus distortion 60 db typ 150 mv rms/60 hz, gain = 2 bandwidth (C3 db) 140 hz clkin = 3.57954 5 mhz referenc e in p u t ref in /ou t input voltage range 2.6 v max 2.4 v + 8% 2.2 v min 2.4 v C 8% input capacitance 10 pf max on-chip refe r e nce nominal 2.4 v at ref in/o u t pin reference error 200 mv max current source 10 a max output impeda nce 3.4 k? min temperature coefficient 30 ppm/ c typ clkin all specifications clkin of 3.579 545 mhz input clock fre quency 4 mhz max 1 m h z m i n logic inputs reset , din, sclk, clki n, and cs input high volt age, v inh 2.4 v min dvdd = 5 v 1 0 % input low voltage, v inl 0.8 v max dvdd = 5 v 1 0 % input current, i in 3 a max t y pically 10 na, v in = 0 v to dvdd input capacitance, c in 1 0 p f m a x logic outputs sag and irq open-drain outputs, 10 k? pull-up resistor output high vol t age, v oh 4 v m i n i sou r ce = 5 ma output low voltage, v ol 0 . 4 v m a x i sin k = 0.8 ma zx and dout output high vol t age, v oh 4 v m i n i sou r ce = 5 ma output low voltage, v ol 0 . 4 v m a x i sin k = 0.8 ma c f output high vol t age, v oh 4 v m i n i sou r ce = 5 ma output low voltage, v ol 1 v m a x i sin k = 7 ma power supply for specified performance avdd 4.75 v min 5 v C 5% 5.25 v max 5 v + 5% dvdd 4.75 v min 5 v C 5% 5.25 v max 5 v + 5% aidd 3 ma max typically 2.0 ma didd 4 ma max typically 3.0 ma _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ___ __ __ __ __ __ __ __ __ __ __ __ __ ___ __ _ 1 see t h e t e rmin olo gy s e ct ion fo r e x pla n at ion of speci f icat ion s . 2 see t h e p l ot s in t h e typical per f orma n c e ch aract e rist ics sect ion . 3 see t h e an alog in put s s e ct ion . +2.1v 1.6ma i oh i ol 200 a c l 50pf 04481-a - 002 to outpu t pin f i g u re 2. l o ad ci r c uit f o r tim i ng spec i f ic at ions
ade7763 r e v. a | pa ge 5 o f 5 6 timing characteristics av dd = d v dd = 5 v 5%, a g nd = d g nd = 0 v , o n -c hi p r e f e r e n c e , clki n = 3.579545 mh z xt al, t min to t max = ?40c t o +85c. ta bl e 2. ti mi n g c h aract e ristic s 1, 2 p a r a m e t e r s p e c u n i t test condition s / c o m m e n t s write timing t 1 5 0 n s m i n cs falling edge to first sclk falling edge. t 2 50 ns min sclk logic high pulse wid t h. t 3 50 ns min sclk logic lo w pulse wid t h. t 4 10 ns min valid data setup time before falling edge of sclk . t 5 5 ns min data hold time after sclk falling edge. t 6 400 ns min minimum time between th e end of data byte tr ansfers. t 7 50 ns min minimum time between byte transfers during a serial wr ite. t 8 1 0 0 n s m i n ) cs hold time after sclk falling edge. read timing t 9 3 4 s m i n minimum time between read c o mmand (i.e., a write to communication regis t er) and data read. t 10 50 ns min minimum time between data b yte transfers dur i ng a multibyte read. t 11 3 0 n s m i n data access time after sclk risi ng ed ge followi ng a write to the communication register. t 12 4 100 ns max bus relinquish time after falling edge of sclk. 1 0 n s m i n t 13 5 1 0 0 n s m a x bus relin q uish time after rising ed ge of cs . 1 0 n s m i n __ __ __ __ __ __ __ __ __ __ __ __ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 1 sa m p le t e st ed dur i n g i n i t ia l rel e a s e a n d a f t e r a n y re desi gn or pr oce s s ch a n ge t h a t coul d a f fect t h i s pa ra m e t e r. a l l i n put si gn al s are s p e c if ie d with tr = tf = 5 ns ( 10% to 90%) and timed fr om a voltage level of 1.6 v. 2 see figure 3, figu r e 4, and the s e rial i nterface section. 3 m i nimum time between read command an d d a ta read f o r al l regis t ers exc e p t wavef o rm regis t er, which is t 9 = 500 ns min. 4 measur ed with the load circuit in figure 2 and define d a s the time r e quired fo r the output to c r oss 0.8 v o r 2.4 v. 5 derived from the measure d time tak e n by the data outputs to change 0.5 v when loade d wit h the circ uit in figure 2. the measu r e d numbe r is the n e x trapo l ate d back to remove the ef fec t s of charging or d i s c harging the 50 pf capacitor. this m e ans that the time quoted in the timing characteris tics is t h e true bus re l i nquis h time of t h e pa rt a n d i s i n de pen d en t of t h e bu s loa d i n g. din sclk cs t 2 t 3 t 1 t 4 t 5 t 7 t 6 t 8 command byte most significant byte least significant byte 1 0 a4 a5 a3 a2 a1 a0 db7 db0 db7 db0 t 7 04481-a - 003 fi g u r e 3 . s e r i a l w r i t e t i m i n g sclk cs t 1 t 10 t 13 0 0 a4 a5 a3 a2 a1 a0 db0 db7 db0 db7 din dout t 11 t 11 t 12 command byte most significant byte least significant byte t 9 04481-a - 004 f i gur e 4 . s e ri al read t i m i ng
ade7763 r e v. a | pa ge 6 o f 5 6 absolute maximum ratings t a = 2 5 c , u n l e ss ot he r w i s e no t e d. ta bl e 3. p a r a m e t e r r a t i n g avdd to ag nd C0.3 v to +7 v dvdd to dg nd C0.3 v to +7 v dvdd to a v dd C0.3 v to +0.3 v analog input voltage to agnd v1p, v1n, v2p, a n d v2n C6 v to +6 v reference input voltage to agn d C0.3 v to av dd + 0.3 v digital input voltage to dgnd C0.3 v to dv dd + 0.3 v digital output v o ltage to dgnd C0.3 v to dv dd + 0.3 v operating tem p erature range industrial C40c to +85c storage temperature range C65c to +150c junction tempe r ature 150c 20-lead ssop, p o wer dissipation 450 mw ja thermal impedance 112c/w lead temperature, soldering vapor phase (60 s) 215c infrared (15 s) 220c s t r e s s es a b o v e t h os e list e d u nde r a b s o l u te m a xim u m r a t i n g s ma y ca us e p e r m a n e n t dama ge to t h e de vi ce. t h is is a st r e ss r a t i ng on ly , an d f u nc t i on a l op e r a t i o n of t h e d e v i c e a t t h e s e or a n y o t h e r con d i t io n s ab o v e t h o s e i ndic a t e d i n t h e op era t io nal s e c t io n o f t h is sp e c if ic a t io n is no t im pl ie d . e x p o sur e t o a b s o l u te max i m u m r a t i ng co ndi t i on s fo r ex tende d p e r i o d s ma y a f fe c t de vice rel i a b i l i t y . esd caution esd (electrostatic discharge) sensitive device. ele c tros tatic charg e s as high as 4000 v readily accumulate on the human body and test eq uipment and can discharge wi thout detection. although this product features proprietary esd protection circu i try, permanent dama ge may occur on devices subjected to high energy electrostatic discharges. theref ore, prop er esd precautions a r e recommended to avoid perform a nce degradation or l o ss of functiona l ity.
ade7763 r e v. a | pa ge 7 o f 5 6 terminology m e a s u r em ent e r ro r the er r o r as s o ci a t e d w i t h t h e e n erg y m e as ur e m en t made b y t h e ad e7763 is def i n e d b y t h e f o l l o w in g f o r m u l a: pe rc e n t er ror = ? ? ? ? ? ? ? ? ? energy true energy true ade7763 register energy 100% p h as e err o r b e t w e e n c h a nne ls t h e d i gi ta l i n t e gr a t o r a n d th e h i g h - p a s s fil t e r (h p f ) i n c h a n n e l 1 ha ve a n o nide a l phas e r e sp o n s e . t o o f fs et t h is phas e r e sp o n s e a nd e q ua li ze t h e phas e r e sp o n s e b e tw e e n chan nels, tw o phas e- co r r e c t i o n n e two r ks a r e place d in c h a n ne l 1: on e fo r t h e dig i t a l in teg r a t o r an d t h e o t h e r fo r t h e hp f . the phas e co r r e c t i o n n e tw o r ks co r r e c t t h e phas e r e s p o n s e o f t h e co r r es p o ndin g co m p on e n t an d en sur e a phas e ma t c h b e t w e e n c h a nnel 1 (c ur r e n t ) a nd c h a nne l 2 (v o l t a g e ) t o wi thin 0.1 o v er a ra n g e o f 45 h z t o 65 h z wi th th e di gi tal in t e gra t o r o f f . w i th t h e d i g i t a l i n t e g r a t or on , t h e ph a s e i s c o r r e c te d to w i t h i n 0 . 4 o v e r a ra n g e o f 45 h z to 65 h z . p o wer s u pply rej e c t i o n th is quan t i f i e s t h e ade 776 3 me asure m e n t er r o r as a p e r c en t a ge o f t h e r e ading w h e n t h e p o w e r su p p lies a r e va r i e d . f o r t h e ac ps r m e asur e m en t, a r e ad in g a t n o m i na l sup p li es (5 v) is t a k e n . a seco n d r e ad in g i s o b ta in ed w i th t h e sa m e in p u t si gnal lev e ls when an ac (17 5 mv r m s/120 h z ) sig n al is in t r o d uced t o the su p p lies. a n y er r o r in t r o d uce d b y t h is ac sig n a l is exp r ess e d as a p e r c e n t a ge o f t h e r e a d ing s e e t h e m e a s ur em e n t er r o r def i ni t i o n . f o r t h e dc psr m e as ur e m en t, a r e adin g a t n o minal s u p p lies (5 v ) i s tak e n . a seco n d r e ad in g i s o b ta in ed w i th t h e sa m e in p u t sig n al le ve ls w h en t h e su p p lies a r e va r i e d 5%. an y er r o r in t r o d uce d is a g a i n exp r es s e d as a p e r c en t a g e o f t h e r e adin g . ad c off s et err o r the dc o f fs et ass o ci a t e d wi t h t h e a n alog in pu ts t o t h e ad cs . i t m e a n s tha t w i t h th e a n alog i n p u t s co nn ect e d t o a g n d , t h e a d cs s t ill see a d c a n alog i n p u t si gn al . th e ma gn i t ud e o f t h e o f fs et dep e n d s o n t h e ga i n an d in p u t r a n g e s e le c t io ns e e t h e t y p i c a l p e rf o r m a n c e ch a r a c t e ris t i c s secti o n . h o w e v e r , wh e n h p f 1 i s s w itc h e d on , t h e of f s e t i s re mo ve d f r om c h an n e l 1 (c ur r e n t ) a nd t h e p o w e r c a lc u l a t io n is n o t a f fe c t e d b y t h is o f fs et . t h e of f s e t s c a n b e r e move d by p e r f or m i ng a n of f s e t c a l i br a t i o n s e e t h e analog i n p u ts s e c t ion. ga in e r r o r the dif f er en ce b e tw e e n t h e m e as ur e d ad c o u t p u t c o de (min us t h e o f fs et) and t h e i d e a l ou t p u t co des e e t h e c h a nne l 1 a d c a nd c h a n nel 2 ad c s e c t io n s . i t is m e asur e d fo r e a ch o f t h e in p u t ra n g es o n cha nne l 1 (0.5 v , 0.25 v , and 0. 125 v). th e dif f er en ce is ex p r es s e d as a p e rcen t a g e o f t h e i d e a l co de .
ade7763 r e v. a | pa ge 8 o f 5 6 pin conf iguration and fu nction descriptions v2n 6 v2p 7 agnd 8 ref in/out 9 dgnd 10 clkin irq sag zx cf 15 14 13 12 11 ade7763 top view (not to scale) dvdd 2 avdd 3 v1p 4 v1n 5 dout sclk cs clkout 19 18 reset 1 din 20 17 16 04481-a - 005 f i g u re 5. pin conf ig ur at i o n (s sop p a ckag e) ta bl e 4. pi n f u nct i o n d e s c ri pt i o ns pin no. mnemonic description 1 reset reset pin for the ade7763. a log i c low on this pi n holds the adcs and digital circuitry (including the serial interface) in a reset condition. 2 d v d d digital power s u pply. t h is pin provides the su pply vo ltage for the digital circuitry. the supply voltage should be maint a ined at 5 v 5% for specified operatio n . t h is pin shou ld be d e coupled to dgnd with a 10 f capacitor i n parallel with a ceramic 100 nf capacitor . 3 a v d d analog power s u pply. t h is pin provides the su pply volt age for the analog circuitry. the supply should be maintained at 5 v 5% for specified operation. minimiz e power supply ripple a n d noise at this pin by using proper decoup li ng. t h e typical performan c e graphs s h ow the power sup p ly re jection perf orm a nce. t h is pin shou ld be decoupled to agnd with a 10 f ca pacitor i n par a lle l with a ceramic 100 nf capacitor. 4, 5 v1p, v1n analog inputs for channel 1. this chan nel is int e nded for use with a di/dt curre nt transducer, i.e., a rogowski c o il or another current sensor such as a shun t or current transformer (ct). these inputs are fully differential volt age inputs with maximum differential in put signal leve ls of 0.5 v, 0.25 v, and 0.125 v, d e pend ing on the full-sca l e se le ctionsee the analog in puts s e ction. chan nel 1 also h a s a pga with gain selections of 1, 2, 4, 8, or 16. th e maximum sig n al lev e l at these pins with respect to agnd is 0 .5 v. both inputs have internal esd protect i on circuitry and ca n sustain an overvo ltage of 6 v without risk of permane n t damage. 6, 7 v2n, v2p analog inputs for channel 2. this ch annel is int e nded for use with the voltage transducer. these inputs are fully differential voltage inputs with a maximu m different ial signal leve l of 0. 5 v. channel 2 al so has a pga with gain selections of 1, 2, 4, 8, or 16. the maxi mu m signal lev e l at these pin s with respect to agnd is 0.5 v. both inputs have internal esd protection circuitry and can sust ain an ov e r voltage of 6 v without risk of perm ane n t damage. 8 a g n d analog ground reference. t h is pin provide s the ground reference for the analog circuitry, i.e., adcs and reference. this pin shou ld be tied to the analog grou nd plane or to the quietest ground reference in the system. use this quiet ground re ferenc e for al l a n alog circuitry, s u ch as antiali a si ng filters and current and voltage transducers. to minimiz e ground noise arou nd the ade 7763, connect the quiet ground plane to the digital ground plane at o n ly one poi nt. it is a ccepta b le to place the entire device on the a n alog ground plane. 9 r e f in /ou t access to the o n -chip voltage reference. the on-chi p referen c e has a n o mina l value of 2.4 v 8% and a typical temperature coefficient of 30 ppm/ c. an ex tern al reference source can a lso b e conne cted at this pin. in either cas e , this pin sh oul d be deco upled to agnd with a 1 f ceramic capacitor. 1 0 d g n d digital ground reference. t h is pin provide s the ground reference for the digital circuitry, i . e . , m u l t i p l i e r , filt er s, and dig i tal-t o -f re que n cy conve r ter . be cau s e the dig i tal retu rn curr ent s in t h e ade7 763 a r e s m a l l , i t i s acceptab le to c o nnect this pin t o the anal og ground plane of the system. however, high bus c a pacitan c e on the dout pin could result in noisy digi tal current, which could affect performance. 1 1 c f calibrati o n frequency logic output. the cf logic o utput gives active power inf o rmation. this ou tput is intended to be used for operational a n d calibr a t ion purposes. the full-scale output freq uency can be adjusted by writing to the cfden and cfnum r e gister ssee th e energy-to-frequency conversion section. 1 2 z x voltage waveform (channel 2) zero-crossing output. th is output toggles logic hi gh and logic low at the zero cro ssing of the d i fferential signal on ch anne l 2see the zer o -cros s ing detection section. 13 sag this open-drain logic output goes active lo w wh en either no zer o crossings are detected or a low voltage thres h ol d (channel 2) is cross e d for a s p ecified du rationsee th e line voltage sag detection se ction. 14 irq interrupt req u e s t output. this is an active low, open-drain logic output. m a skable interrupts in clud e active energy register rollover, active e n ergy register at ha lf level, a n d arrivals of new waveform samp lesse e the interrupts sectio n.
ade7763 rev. a | page 9 of 56 pin no. mnemonic description 15 clkin master clock for adcs and digital sign al processing. an external clock can be provided at this logic input. alternatively, a parallel resonant at crystal can be connected across cl kin and clkout to provide a clock source for the ade7763. the clock frequency for specified operation is 3.579545 mhz. ceramic load capacitors between 22 pf and 33 pf should be used with the gate oscillator circ uit. refer to the crystal manufacturers data sheet for load capacitance requirements. 16 clkout a crystal can be connected across this pin and clkin, as described for pin 15, to provide a clock source for the ade7763. the clkout pin can drive one cmos load wh en either an external clock is supplied at clkin or a crystal is being used. 17 cs chip select. part of the 4-wire spi serial interface. this active low logic input allows the ade7763 to share the serial bus with several other devicessee the serial interface section. 18 sclk serial clock input for the synchronous serial interface. all serial data transfers are synchronized to this clocksee the serial interface section. the sclk has a schmitt-trigger input for use with a clock source that has a slow edge transition time, such as an opto-isolator output. 19 dout data output for the serial inte rface. data is shifted out at this pin upon the rising edge of sclk. this logic output is normally in a high impedance state, unless it is driving data onto the serial data bussee the serial interface section. 20 din data input for the serial interface. data is shifted in at this pin u pon the falling edge of sclksee the serial interface section.
ade7763 rev. a | page 10 of 56 typical perf orm ance cha r acte ristics full-scale current (%) e rror (%) 0.1 ?0.6 ?0.2 ?0.3 ?0.4 ?0.5 0.1 0 0.4 0.3 0.2 ?0.1 1 1 0 100 04481-a - 006 gain = 1 integrator off internal reference ?40c, pf = 0.5 +85c, pf = 0.5 +25c, pf = 0.5 +25 c, pf = 1 f i gure 6 . a c ti v e ener gy err o r a s a p e r c enta ge o f rea d i n g (g a i n = 1 ) o v er p o wer f a c t o r with intern a l r e fe renc e and integ r ato r o ff ? 1.0 ? 0.8 ? 0.6 ? 0.4 ? 0.2 0 0.2 0.4 0.6 0.8 1.0 e rror (%) full-scale current (%) 0.1 10 1 100 04481-a - 007 gain = 8 integrator off internal reference +85c, pf = 1 +25c, pf = 1 ?40c, pf = 1 f i gure 7. ac tive e n e r gy as a p e r c e n tag e of re adi n g (g a i n = 8) o v er t e mpe r atu r e with intern a l r e fe renc e and integ r ato r o ff ? 1.0 ? 0.8 ? 0.6 ? 0.4 ? 0.2 0 0.2 0.4 0.6 0.8 1.0 e rror (%) full-scale current (%) 0.1 10 1 100 04481-a - 008 gain = 8 integrator off internal reference +85 c, pf = 0.5 +25 c, pf = 0.5 ? 4 0 c, pf = 0.5 +25c, pf = 1 f i gure 8 . a c ti v e ener gy err o r a s a p e r c enta ge o f rea d i n g (g a i n = 8 ) o v er p o wer f a c t o r with intern a l r e fe renc e and integ r ato r o ff ? 1.0 ? 0.8 ? 0.6 ? 0.4 ? 0.2 0 0.2 0.4 0.6 0.8 1.0 e rror (%) full-scale current (%) 0.1 10 1 100 04481-a - 009 gain = 8 integrator off external reference +85c, pf = 1 ?40c, pf = 1 +25 c, pf = 1 f i gure 9 . a c ti v e ener gy err o r a s a p e r c enta ge o f rea d i n g (g a i n = 8 ) o v er t e mpe r at u r e wit h e x te rn al r e f e renc e and integ r at o r o f f ? 1.0 ? 0.8 ? 0.6 ? 0.4 ? 0.2 0 0.2 0.4 0.6 0.8 1.0 e rror (%) full-scale current (%) 0.1 10 1 100 04481-a - 010 gain = 8 integrator off external reference +85c, pf = 0.5 +25c, pf = 0.5 ? 4 0c, pf = 0.5 +25 c, pf = 1 f i g u re 10. ac t i ve e n er g y e rror as a p e r cent a g e of r e ading (g ain = 8) o v er p o wer f a c t o r with e x te rn al r e f e renc e and integ r ato r o ff ? 0.5 ? 0.4 ? 0.3 ? 0.2 ? 0.1 0 0.1 0.2 0.3 0.4 0.5 e rror (%) full-scale current (%) 0.1 10 1 100 04481-a - 080 gain = 8 integrator off internal reference 5.25v 5.00v 4.75v f i g u re 11. ac t i ve e n er g y e rror as a p e r cent a g e of r e ading (g ain = 8) o v er p o wer s u p p ly with intern a l r e fe renc e and integ r ato r o ff
ade7763 rev. a | page 11 of 56 ? 0.6 ? 0.4 ? 0.2 0 0.2 0.4 0.6 0.8 1.0 1.2 e rror (%) 45 47 49 51 53 55 57 59 61 63 65 frequency (hz) 04481-a - 012 gain = 8 integrator off internal reference pf = 0.5 pf = 1 f i g u re 12. ac t i ve e n er g y e rror as a p e r cent a g e of r e ading (g ain = 8) o v er f r eq uenc y wit h inte rna l r e f e rence and integr a t o r o f f ? 1.0 ? 0.8 ? 0.6 ? 0.4 ? 0.2 0 0.2 0.4 0.6 0.8 1.0 e rror (%) full-scale current (%) 0.1 10 1 100 04481-a - 013 gain = 8 integrator off internal reference pf = 1 pf = 0.5 f i g u re 13. ir m s e rror as a p e r c e n t a g e of r e ad ing (g ain = 8) wi th internal referenc e a n d int e g r a t or o ff ? 0.5 ? 0.4 ? 0.3 ? 0.2 ? 0.1 0 0.1 0.2 0.3 0.4 0.5 e rror (%) full-scale voltage (%) 1 1 0 100 04481-a - 020 gain = 1 external reference f i g u re 14. v r m s e rror as a p e r c e n t a g e of r e ad ing (g ain = 1) with e x te rn al r e f e renc e ? 1.0 ? 0.8 ? 0.6 ? 0.4 ? 0.2 0 0.2 0.4 0.6 0.8 1.0 e rror (%) full-scale current (%) 0.1 10 1 100 04481-a - 016 gain = 8 integrator on internal reference +85 c, pf = 0.5 +25 c, pf = 1 ? 4 0 c, pf = 0.5 +25c, pf = 0.5 f i g u re 15. ac t i ve e n er g y e rror as a p e r cent a g e of r e ading (g ain = 8) o v er p o wer f a c t o r with intern a l r e fe renc e and integ r ato r o n ? 1.0 ? 0.8 ? 0.6 ? 0.4 ? 0.2 0 0.2 0.4 0.6 0.8 1.0 e rror (%) full-scale current (%) 0.1 10 1 100 04481-a - 015 gain = 8 integrator on internal reference +85c, pf = 1 +25c, pf = 1 ?40c, pf = 1 f i g u re 16. ac t i ve e n er g y e rror as a p e r cent a g e of r e ading (g ain = 8) o v er t e mpe r at u r e wit h e x te rn al r e f e renc e and integ r at o r o n ? 2.0 ? 1.5 ? 1.0 ? 0.5 0 0.5 1.0 1.5 2.0 2.5 3.0 e rror (%) 45 47 49 51 53 55 57 59 61 63 65 frequency (hz) 04481-a - 017 gain = 8 integrator on internal reference pf = 0.5 pf = 1 f i g u re 17. ac t i ve e n er g y e rror as a p e r cent a g e of r e ading (g ain = 8) o v er f r eq uenc y wit h inte rna l r e f e rence and integr a t o r o n
ade7763 rev. a | page 12 of 56 ? 0.5 ? 0.4 ? 0.3 ? 0.2 ? 0.1 0 0.1 0.2 0.3 0.4 0.5 e rror (%) full-scale current (%) 0.1 10 1 100 04481-a - 081 gain = 8 integrator on internal reference 5.25v 5.00v 4.75v f i g u re 18. ac t i ve e n er g y e rror as a p e r cent a g e of r e ading (g ain = 8) o v er p o wer s u p p ly with intern a l r e fe renc e and integ r ato r o n ? 0.5 ? 0.4 ? 0.3 ? 0.2 ? 0.1 0 0.1 0.2 0.3 0.4 0.5 e rror (%) full-scale current (%) 0.1 10 1 100 04481-a - 019 gain = 8 integrator on internal reference pf = 0.5 pf = 1 f i g u re 19. ir m s e rror as a p e r c e n t a g e of r e ad ing (g ain = 8) wi th internal referenc e a n d int e g r a t or o n 0 2 4 6 8 10 hits 12 14 16 ? 1 5 ? 10 ?5 0 5 10 15 20 ch1 offset (0p5v_1x) (mv) 04481-a - 021 f i g u re 20. cha nne l 1 o f f s et (g ai n = 1) v dd 10 f 10 f 10 f 100nf 100nf a v dd d v dd reset din dout sclk cs clk out clkin irq sag zx cf a gnd dgnd v1p v1n v2n v2p ref in/out u1 ade7763 t o spi b u s (u se d o n l y f o r cal i brat i o n) 22pf 22pf y1 3.58mhz not connected u3 ps2501-1 i di/dt current sensor 100 ? 1k ? 33nf 33nf 100 ? 1k ? 33nf 33nf 1k ? 33nf 600k ? 110v 1k ? 33nf 100nf channel 1 gain = 8 channel 2 gain = 1 to f r e q ue nc y co unt e r 04481-a - 022 fi g u r e 21 . t est c irc u it for p er f o r m a n ce cur v es w i th integ r ator o n ct turn ratio = 1800:1 channel 2 gain = 1 rb 10 ? 1.21 ? gain 1 (ch1) 1 8 not connected v dd 10 f1 f 100nf 100nf din dout sclk cs clk out clkin irq sag zx cf a gnd dgnd v1p v1n v2n v2p ref in / o u t u1 ade7763 t o s p i bus (us e d o n l y f o r ca l i b rati o n) 22pf 22pf y1 3.58mhz u3 ps2501-1 i current transformer 1k ? 33nf 1k ? 33nf 1k ? 33nf 600k ? 0 rb 110v 1k ? 33nf 10 f 100nf to fr e q u e n c y co un t e r 04481-a - 023 a v dd d v dd reset f i gure 2 2 . t e st c i rcui t fo r p e r f o r m a nce c u r v es wi th integ r a t o r o ff
ade7763 rev. a | page 13 of 56 theory of operation analog inputs the ad e7763 has tw o f u l l y dif f er en t i al v o l t a g e in p u t c h a n ne ls. the max i m u m dif f er e n t i a l i n put v o l t a g e fo r i n pu t p a irs v1 p / v 1 n a nd v2p/ v2n i s 0.5 v . i n ad di t i o n , t h e m a x i m u m sig n a l l e vel o n a n alog in p u t s fo r v1p/v1n a nd v2p/v2n is 0.5 v w i t h re sp e c t to a g n d . e a ch a n a l og i n pu t cha n n e l has a p r og ra mma b l e ga in am plif ier (pga) wi th p o ssi b l e ga in s e lec t io n s o f 1, 2, 4, 8, a nd 16. th e g a in s e l e cti o n s a r e mad e b y w r i t in g t o th e ga in r e gi s t er see f i g u r e 24 . bi ts 0 t o 2 s e le c t t h e ga in fo r t h e pga in c h a n ne l 1; t h e gain s e le c t io n fo r t h e pg a i n c h a n ne l 2 is made v i a bi ts 5 t o 7. f i gur e 23 sh o w s ho w a gain s e lec t io n f o r cha nne l 1 is made usin g t h e ga in r e g i s t er . v1p v1n v in k v in + gain[7:0] 76 5 4 3 2 1 0 00 0 0 0 0 0 0 76 5 4 3 2 1 0 00 0 0 0 0 0 0 gain (k) selection offset adjust (50mv) ch1os[7:0] bits 0 to 5: sign magnitude coded offset correction bit 6: not used bit 7: digital integrator (on = 1, off = 0; default off) 04481-a - 024 f i g u re 23. pg a in c h ann e l 1 i n addi tion t o t h e pg a, c h a n ne l 1 als o has a f u l l -s cale in p u t ra n g e s e le c t io n fo r t h e ad c. th e ad c a n alog in p u t ra n g e s e le c t ion is a l s o made usin g t h e ga in r e g i ster s e e f i gur e 24. a s p r e v io usly m e n t io n e d , t h e m a xi m u m dif f er en t i a l in p u t v o l t a g e is 0.5 v . h o wever , b y usin g b i ts 3 a nd 4 in t h e g a in r e g i st er , t h e maxim u m ad c in p u t v o l t a g e ca n be s e t t o 0.5 v , 0.25 v , o r 0.125 v . this is ac hiev e d b y ad j u s t in g t h e ad c r e f e r e n c es e e t h e refer e n c e c i r c ui t s e c t io n. t a b l e 5 s u mma r i z es t h e maxim u m dif f er en tial in p u t s i g n al le ve l o n c h anne l 1 f o r th e v a r i ou s a d c r a nge an d g a i n s e l e c t i o ns . t a b l e 5 . m a x i mum inp u t sign al l e v e l s fo r ch ann e l 1 adc input r a nge selection max signal channel 1 0.5 v 0.25 v 0.125 v 0.5 v gain = 1 ? ? 0.25 v gain = 2 gain = 1 ? 0.125 v gain = 4 gain = 2 gain = 1 0.0625 v gain = 8 gain = 4 gain = 2 0.0313 v gain = 16 gain = 8 gain = 4 0.0156 v ? gain = 16 gain = 8 0.00781 v ? ? gain = 16 gain register* channel 1 and channel 2 pga control 7 6 5 4 3 2 1 0 0 0 0 0 0 0 0 0 addr: 0x0a * register contents show power-on defaults pga 2 gain select 000 = 1 001 = 2 010 = 4 011 = 8 100 = 16 pga 1 gain select 000 = 1 001 = 2 010 = 4 011 = 8 100 = 16 channel 1 full-scale select 00 = 0.5v 01 = 0.25v 10 = 0.125v 04481-a-025 f i gure 2 4 . a n al o g g a i n regi st er i t is als o p o s s i b l e t o ad j u s t o f fs et er r o rs o n c h a nne l 1 an d cha nne l 2 b y wr i t in g t o t h e o f fs et co r r ec tio n r e g i s t ers (ch1os a nd ch2os , r e s p e c t i ve l y ). th es e r e g i s t ers al lo w cha nne l o f fs ets in t h e ra n g e 20 mv t o 50 mv (d ep en di n g o n t h e ga in s e t t in g) to b e re mo ve d. n o te t h a t i t i s not ne c e ss ar y to p e r f or m an of f s e t co r r e c t i o n in an en erg y m e as ur em e n t a p plic a t io n if hp f in cha nne l 1 is s w i t ch ed on. f i gur e 25 sh o w s t h e ef f e c t o f o f fs ets o n t h e r e al p o wer calc u l a t io n. a s s een f r o m f i gur e 25, a n o f fs et o n c h a n nel 1 and c h a n nel 2 c o n t r i b u tes a dc co m p on e n t a f te r m u l t i p lica t i o n . b e ca us e this dc co m p on en t is extrac t e d b y lp f 2 t o g e n e ra t e t h e ac t i v e (r e a l) p o w e r info r m a t ion, t h e o f fs ets con t r i b u te an er r o r t o t h e ac t i v e p o w e r c a l c u l a t ion. thi s p r oble m is e a si ly a v o i de d b y ena b l i n g h p f in c h a n ne l 1. by r e m o v i n g t h e o f fs et f r o m a t le as t one channe l , n o er r o r co m p on en t is gen e r a te d a t dc b y t h e m u l t i p li c a t i o n . er r o r ter m s a t co s( t) a r e r e m o ve d b y lpf 2 a n d b y i n teg r a t io n o f t h e ac t i ve p o w e r sig n a l i n t h e a c t i v e e n e r g y r e g i st er (a ene r g y [2 3:0] ) s e e t h e e n e r g y cal c ula t i o n s e ct i o n .
ade7763 rev. a | page 14 of 56 dc component (including error term) is extracted by the lpf for real power calculation frequency (rad/s) i os v v os i v os i os v i 2 0 2 04481-a - 026 f i g u re 25. e f f e c t of chann e l o f f s et s o n t h e r e al p o wer cal c ul at io n the co n t en ts o f t h e o f fs et co r r e c t i o n r e g i s t ers a r e 6-b i t, sig n an d ma g n i t u d e co de d . th e w e ig h t o f t h e l s b de p e nds o n t h e ga i n s e t t ing, i . e ., 1, 2, 4, 8, o r 16. t a b l e 6 sh o w s t h e co r r ec ta b l e o f fs et sp a n fo r e a ch o f t h e gain s e t t in g s a nd t h e ls b weig h t (m v) fo r t h e o f fs et co r r e c t i o n r e g i s t ers. th e maxim u m v a l u e t h a t ca n b e wr i t t e n t o t h e o f fs et co r r ec tio n r e g i s t ers is 31ds ee f i gur e 26. f i gur e 26 sh o w s th e r e la ti o n s h i p bet w een t h e o f fse t co rr ecti o n r e g i s t er co n t e n t s a nd t h e o f fs et (mv) o n t h e a n alog in p u ts fo r a g a i n of 1 . t o p e r f or m an of f s e t a d j u st me n t , c o n n e c t t h e an a l o g in p u ts t o a g nd; t h er e sh o u ld b e n o sig n al on ei t h er c h a n ne l 1 or c h an n e l 2 . a re a d f r om c h a nnel 1 o r c h a n nel 2 usin g t h e wa v e fo r m r e g i s t er indi ca t e s t h e o f fs et in t h e channe l . this o f fs et ca n b e can c ele d b y wr i t ing a n e q ua l and o p p o si te o f fs et va l u e to t h e c h a n ne l 1 o f fs et r e g i s t er , o r a n e q ual va l u e to t h e c h ann e l 2 o f fs et r e g i s t er . th e o f fs et co r r e c t i o n can b e co nf i r m e d b y p e r f o r min g a n ot h e r r e ad . n o t e t h a t w h en ad j u st in g t h e o f fs et of c h a nnel 1, t h e dig i t a l i n teg r a t or a n d t h e hpf sh o u ld b e dis a b l e d . ta bl e 6. offs et corr ecti on ra ngec h a n ne ls 1 a n d 2 gain correctable span ls sie 1 50 mv 1.61 mv/lsb 2 37 mv 1.19 mv/lsb 4 30 mv 0.97 mv/lsb 8 26 mv 0.84 mv/lsb 16 24 mv 0.77 mv/lsb ch1os[5:0] sign + 5 bits + 50mv offset adjust 0x3f 0x00 0x1f ?50mv 0mv sign + 5 bits 01,1111b 11,1111b 04481-a - 027 f i g u re 26. cha nne l 1 o f f s et c o rrec t ion range ( g ain = 1) th e c u r r en t a n d v o l t a g e r m s o f fs e t s ca n b e ad j u s t ed wi t h t h e irmsos a n d vrmsos r e gis t er s s e e t h e c h a n n e l 1 r m s o f f s e t c o m p en s a t i o n a n d c h a n n e l 2 rms of fs et c o m p e n s a t i on secti o n s . di/dt current sens or and digital integrator a di/d t s e n s o r det e c t s c h an g e s in ma g n etic f i e l d ca us e d b y ac c u r r en t. f i gur e 27 s h o w s t h e p r in c i ple o f a di/ d t c u r r en t s e n s o r . magnetic field created by current (directly proportional to current) + emf (electromotive force) ? induced by changes in magnetic flux density (di/dt) 04481-a - 028 f i g u re 27. p r inc i pl e of a d i /dt cur r ent s e ns or the f l ux den s i t y o f a ma g n et ic f i eld ind u ce d b y a c u r r en t is d i re c t ly prop or t i on a l to t h e m a g n itu d e of t h e c u r r e n t . c h ange s in t h e ma g n et ic f l ux den s i t y p a ssin g thr o ug h a c o nd uc t o r lo o p g e n e ra t e a n e l ec tr o m o t i v e f o r c e (emf) be tw ee n th e t w o en d s o f th e loo p . th e emf i s a v o l t a g e si gn al th a t i s p r o p o r ti o n al t o th e di/ d t o f t h e c u r r en t. th e v o l t a g e o u t p u t f r o m t h e di/d t c u r r en t s e n s o r is det e r m in ed b y t h e m u t u al ind u c t an c e betw e e n t h e c u r r en t-ca r r y i ng co nd uc to r and t h e di/ d t s e n s o r . th e c u r r e n t sig n a l m u st b e re co ver e d f r o m t h e di /d t sig n a l b e fo r e i t ca n b e us e d . an in t e g r a t o r is t h er efo r e n e c e s s a r y t o r e s t o r e th e s i g n a l t o i t s o r ig ina l f o r m . th e ad e7 763 h a s a bu i l t - i n d i g i t a l i n t e g r a t or t o r e co v e r t h e c u r r en t sig n al f r o m t h e di/ d t s e n s o r . th e dig i t a l i n t e g r a t or on c h an n e l 1 i s s w it che d of f b y d e f a u l t w h e n t h e ad e7763 is p o w e r e d u p . s e t t ing th e m s b o f ch1os r e g i s t er t u r n s o n t h e in teg r a t o r . f i gur e 28, f i gur e 29, f i gur e 30, a nd f i gur e 31 sh o w t h e ma g n i t ude and phas e r e s p on s e o f t h e dig i t a l in teg r a t o r . frequency (hz) 10 gain ( d b) 0 ?10 ?20 ?30 ?40 ?50 10 2 10 3 04481-a - 029 f i gur e 2 8 . c o m b ined ga in re sp onse o f the d i g i t a l in teg r at or a n d phas e co mpe n s a to r
ade7763 rev. a | page 15 of 56 frequency (hz) 10 2 10 3 04481-a - 030 ? 88.0 ph a se ( d egrees) ? 88.5 ? 89.0 ? 89.5 ? 90.0 ? 90.5 f i g u re 29. co mbi n e d p h as e r e s p ons e of t h e d i g i t a l i n teg r at or and p h as e co mpe n s a to r frequency (hz) ? 1.0 ? 6.0 40 70 45 gain ( d b) 50 55 60 65 ? 1.5 ? 2.0 ? 2.5 ? 3.5 ? 4.5 ? 5.5 ? 3.0 ? 4.0 ? 5.0 04481-a - 031 f i gur e 3 0 . c o m b ined ga in re sp onse o f the d i g i t a l in teg r at or a n d phas e co mpe n s a to r ( 40 h z to 7 0 h z ) ? 89.75 ?89.80 ?89.85 ?89.90 ? 89.95 ?90.00 frequency (hz) ph a se ( d egrees) 40 45 70 50 55 60 65 ?90.05 ?90.10 ? 89.70 04481-a - 032 f i g u re 31. co mbi n e d p h as e r e s p ons e of t h e d i g i t a l in teg r at or a n d phas e co mpe n s a to r ( 40 h z to 7 0 h z ) n o te t h a t t h e i n te g r a t or h a s a C 2 0 db / d e c a t te n u a t i o n a n d a p p r o x im a t e l y a C90 phas e shif t. w h e n com b i n e d wi t h a di /d t s e n s o r , t h e r e s u l t in g ma g n i t u d e a nd phas e r e s p on s e sh o u l d b e a f l a t ga i n o v er t h e f r e q uen c y b a nd o f in ter e st. t h e di /d t s e ns o r has a 20 db /de c ga in. i t als o g e nera t e s sig n if ica n t hig h f r e q u e nc y noi s e , ne c e ss i t a t i n g a more e f fe c t ive an t i a l i a s i ng f i lte r t o a v o i d n o i s e d u e t o alias i n g s e e t h e a n t i al ias f i l t er s e c t io n. w h en t h e dig i t a l in teg r a t o r is s w i t ch ed o f f , t h e ad e7763 ca n b e u s ed di r e ctl y wi th a c o n v en ti o n al cu rr e n t s e n s o r s u c h as a c u rr en t tra n sfo r m e r (ct) o r wi th a lo w r e sis t a n ce c u r r en t sh u n t. zero-crossing detection the ad e 776 3 has a zer o -cr o ssing det e c t ion c i r c ui t on cha n nel 2. this zer o cr ossin g is us e d t o p r o d uce an ext e r n a l z e r o - c r o s s i n g sig n a l ( z x), w h i c h is u s e d i n t h e c a l i br a t i o n m o d e ( s e e t h e c a l i b r a t i n g an e n e r g y m e te r s e c t i o n ) . th i s sig n al i s also use d t o ini t i a te a te m p er a t ure me asur e m en t ( s e e t h e t e m p e r atu r e m e as ur emen t s e c t io n). f i g u re 3 2 s h o w s how t h e z e ro - c ro ss i n g s i g n a l i s ge ne r a te d f r om th e o u t p u t o f lp f1. 1, 2, 1, 8, 16 adc 2 reference 1 lpf1 f ? 3db = 140hz ?63 % t o + 6 3 % f s pga2 {gain[7:5]} v2p v2n v 2 zero crossing zx to m u lt i p lie r 2.32 @ 60hz 1.0 0.93 zx v2 lpf1 04481-a - 033 f i g u re 32. zero - c r o s s i ng d e tec t i o n on chann e l 2 t h e zx s i gn al g o e s l o gi c h i gh u p o n a pos i ti v e - g o i n g ze r o c r o s s i ng an d l o g i c l o w up o n a ne g a t i ve - g oi ng z e ro c r o s s i ng on c h a n n e l 2 . t h e z x s i g n a l i s g e ne r a te d f r om t h e output of l p f 1 . lp f1 has a sing le p o le a t 140 h z (@ clki n = 3.579545 mh z). a s a r e s u l t , t h ere is a phas e lag b e tw e e n t h e a n alog in p u t sig n a l v 2 an d t h e output of l p f 1 . t h e ph a s e re sp ons e of t h i s f i lte r i s sho w n i n t h e c h a n nel 2 s a m p l i ng s e c t ion . t h e phas e l a g r e sp o n s e o f lp f1 r e s u l t s in a time de l a y o f a p p r o x ima t e l y 1.14 m s (@ 60 h z ) between t h e zer o cr os sin g o n t h e a n a l o g i n p u t s o f c h an nel 2 and t h e r i s i n g o r f a l l i n g e d ge o f z x .
ade7763 rev. a | page 16 of 56 z e r o -cr o ssin g d e t e c t ion a l s o dr iv es t h e zx f l a g i n t h e i n t e r r u p t st a t u s re g i ste r . a n ac t i ve l o w i n t h e ir q output a p p e ar s i f t h e co r r es p o nding b i t in t h e in t e r r u p t enab l e reg i st er is s e t t o l o g i c 1. the f l a g in t h e i n t e r r u p t s t a t us reg i s t er an d t h e ir q output are s e t t o t h e i r def a u l t va l u es w h en r e s e t (rst st a t us) is r e ad i n t h e in te r r u p t st a t u s re g i ste r . zero-crossing timeo u t z e ro - c ro ss i n g d e te c t i o n h a s an a s s o c i ate d t i me out re g i ste r , zxto u t . this un sig n e d , 12 -bi t r e g i ster is de crem e n te d ( 1 ls b ) ev er y 128/clki n s e con d s. th e r e g i s t er is r e s e t t o i t s us er - p r og ram m e d , f u l l - s ca le v a l u e w h en a zer o cr o s si ng on c h an nel 2 is de t e c t e d . the de f a u l t p o w e r - on va l u e i n t h i s re g i st er i s 0 x f f f . i f the in t e r n al reg i s t er decr em en ts t o 0 bef o r e a zer o cr os sin g is dete c t e d and t h e dissa g b i t i n t h e mo de r e g i ster is l o g i c 0, t h e sa g p i n wi l l go ac t i ve lo w . t h e a b s e n c e o f a zer o cr ossin g is a l s o indi ca te d on t h e ir q p i n if t h e zxt o ena b le b i t in t h e in t e r r u p t ena b le r e g i s t er is s e t t o l o g i c 1. i r r e s p e c ti v e o f t h e ena b le b i t s e t t ing, t h e z x t o f l ag in t h e in t e r r u p t st a t us r e g i ste r is al wa ys s e t w h en t h e in ter n al zxto ut r e g i ster is de cr em e n te d to 0s e e t h e i n ter r u p ts s e c t io n. the z x ou t r e g i ster , a d dr ess 0x 1d , ca n b e wr i tten to a nd r e a d f r o m b y t h e us e r s e e t h e s e r i a l i n ter f ace s e c t i o n. th e r e s o l u tio n o f t h e r e g i s t er is 128 /clki n s e co n d s p e r ls b; th er ef o r e , t h e maxim u m de l a y f o r a n in t e r r u p t is 0.15 s e co nds (128/clki n 2 12 ). f i g u re 3 3 s h o w s t h e z e ro - c ro ss i n g t i me out d e t e c t i o n w h e n t h e line v o l t a g e s t a y s a t a f i xed dc le v e l f o r m o r e than cl kin/128 zxto u t s e conds. 12-bit internal register value zxtout channel 2 zxto detection bit 04481-a - 034 f i gure 33. zero - c r o s s i ng t i me out d e te c t ion period measurement the ad e7763 p r o v ides t h e p e r i o d m e as ur em en t o f th e l i n e . the p e ri od r e g i s t er is a n un s i g n e d , 16-b i t r e g i s t er t h a t is u p da te d e v er y p e r i o d an d a l w a y s has a n ms b o f zer o . w h en clki n = 3.579545 mh z, th e r e s o l u t i o n o f this r e g i s t er is 2.2 m s /ls b , whic h r e p r es en ts 0. 013% w h en t h e line f r eq uen c y is 60 h z . w h e n t h e lin e f r e q uen c y is 60 h z , t h e va l u e o f t h e p e r i o d reg i st er is a p p r o x ima t e l y 7457 d. the l e ng th o f t h e reg i st er e n a b l e s t h e meas ur em en t o f line f r eq uen c ies as lo w as 13.9 h z . the p e r i o d reg i st er is st ab l e a t 1 l s b w h e n t h e li ne is est a b l i s h e d a nd t h e m e as ur em e n t do es n o t cha n g e . thi s f i l t er is as s o c i a t e d wi th a s e t t l i n g t i m e o f 1.8 s e co nds bef o r e the meas ur emen t is s t a b le . s e e t h e c a l i b r a t ing a n en erg y m e t e r s e c t io n fo r m o r e o n t h e p e r i o d r e g i st er . power supply monitor the ad e7763 c o n t a i n s a n on-chi p p o wer s u p p ly m o ni t o r . th e ana l o g su p p ly ( a v d d ) is c o n t i n u o u sly mon i tore d. i f t h e s u p p l y is les s tha n 4 v 5%, t h e ad e7 763 wil l g o in t o a n inac ti v e sta t e a nd n o en erg y wil l acc u m u la te. this is us ef u l to en s u r e co r r e c t de vice op er a t io n d u r i n g p o w e r - u p a nd p o w e r - do wn st a g es. i n a d d i t i o n , b u i l t - i n h y st er es is and f i l t er ing hel p p r e v e n t f a l s e t r i g ge r i ng d u e t o noi s y suppl i e s . av dd 5v 4v 0v ade7763 power-on inactive state sag ina ctive a c tive ina ctive time 04481- a- 035 f i gure 34. o n - c hip p o w e r su p p ly m o ni tor a s s een in f i gur e 34, the tr ig g e r lev e l is n o mina l l y s e t a t 4 v . the t o lera nce on t h is t r ig ger le v e l is ab o u t 5 %. t h e sa g pi n ca n als o be us e d as a p o w e r s u p p l y m o ni t o r in p u t t o t h e m c u . the sa g p i n g o es log i c lo w w h en t h e ad e7763 is in i t s inac ti v e st a t e. t h e p o we r su p p ly and de c o u p l i ng for t h e p a r t shou l d b e s u ch t h a t t h e r i p p le a t a v dd do es n o t exce e d 5 v 5%, as sp e c if ie d fo r n o r m a l o p era t ion.
ade7763 rev. a | page 17 of 56 line vol t a g e sag det e ctio n i n addi t i on t o det e c t i n g t h e los s o f t h e li ne v o l t ag e w h en t h er e a r e n o zer o cr os sin g s o n t h e v o l t a g e c h a n ne l , t h e ad e7763 can a l s o b e pro g r a mme d to de te c t w h en t h e a b sol u t e val u e o f t h e lin e v o l t age dro p s b e lo w a p e a k v a lu e f o r a s p e c i f i e d n u m b e r of l i n e c y cles. this co ndi t i on is i l l u st r a te d i n f i gur e 35. sagcyc[7:0] = 0x04 3 line cycles sag reset high when channel 2 exceeds saglvl[7:0] full scale sa gl vl[7:0] sag channel 2 04481- a- 036 f i g u re 35. s a g d e te c t ion i n f i gur e 35 t h e line v o l t a g e fal l s b e lo w a thr e shold tha t has b e e n s e t i n t h e s a g le ve l r e g i s t er (sa g l v l[7:0]) fo r t h r e e line c y cles. th e q u an t i t i es 0 an d 1 a r e n o t v a li d fo r t h e sa gc y c r e g i s t er , an d t h e co n t e n ts r e p r es en t on e m o r e t h a n t h e des i r e d n u mb e r of f u l l l i ne c y cl e s . f o r ex am pl e, i f t h e d i s s a g b i t in t h e mo de r e g i ster is l o g i c 0 a n d t h e s a g c y c l e re g i s t e r (sa g cy c[7:0]) co n t a i n s 0x04, th e sa g pi n g o e s a c t i ve l o w a t t h e end o f t h e t h ir d li ne c y cle f o r w h ich t h e li ne v o l t a g e (c ha nne l 2 sig n al) fal l s b e lo w t h e t h r e sh old . a s i s th e c a s e wh e n z e r o c r os s i n g s ar e n o lo n g er dete c t e d , t h e s a g e v en t is als o r e co r d e d b y s e t t in g t h e sa g f l ag in t h e in t e r r u p t st a t us r e g i ste r . i f t h e sa g enable b i t is s e t t o l o g i c 1, t h e ir q log i c o u t p u t wil l g o ac t i v e lo w s e e t h e i n ter r u p ts s e c t ion. th e sa g pi n g o e s l o g i c h i g h a g ai n w h e n t h e ab s o l u te va l u e o f t h e sig n a l on c h anne l 2 exc e e d s t h e l e ve l s e t i n t h e s a g l e vel reg i st er . thi s is sho w n in fi g u r e 3 5 w h e n t h e sa g pi n go e s h i g h ag ai n d u r i ng t h e f i f t h l i n e c y c l e fr o m th e ti m e wh e n th e si gn a l o n c h a n n e l 2 fi r s t d r o p ped b e l o w th e th r e s h o l d l e v e l . sag level set the co n t en ts o f t h e s a g l e v e l r e g i s t er (1 b y t e ) a r e co m p a r e d t o t h e a b s o l u t e va l u e o f t h e m o s t s i g n if ican t b y t e ou t p ut f r o m lp f1 a f t e r i t is shif t e d lef t b y one b i t. f o r exa m p l e , the n o minal maxim u m co de f r o m lp f1 wi t h a f u l l -s cale sig n al o n c h a n ne l 2 is 0x2518s e e t h e chann e l 2 sam p lin g s e c t ion. s h if ting o n e b i t lef t g i v e s 0x4a30. ther ef o r e , wr i t in g 0x4 a t o t h e s a g l e v e l r e gis t e r p u ts th e sa g de t e cti o n lev e l a t full s c ale . w r i t i n g 0 x 0 0 or 0x01 p u ts t h e s a g det e c t io n le vel a t 0. th e sa g le v e l r e g i st er is co m p a r ed t o t h e m o s t s i g n if ican t b y t e o f a wa vef o r m s a m p le a f ter t h e sh if t le f t , a nd d e te c t ion o c c u rs w h e n t h e con t e n ts o f t h e s a g l e v e l r e g i s t er a r e g r e a t e r . peak detec t io n the ad e7763 c a n als o b e p r og ra mmed t o det e c t w h en t h e a b s o l u t e val u e of t h e v o l t a g e o r c u r r en t cha n ne l exce e d s a sp e c if ie d p e a k v a l u e . f i gur e 36 i l l u st ra t e s t h e b e ha vio r o f t h e p e a k dete c t io n fo r t h e vol t a g e cha nnel. b o t h c h annel 1 a nd c h a n nel 2 a r e m o n i to r e d a t t h e s a m e t i m e . pkv reset low when rststatus register is read vpklvl[7:0] v 2 read rststatus register pkv interrupt flag (bit 8 of status register) 04481-a - 037 f i g u re 36. p e ak l e vel d e tec t i o n f i gur e 36 sh o w s a li n e vol t a g e e x ce e d in g a t h r e sh old t h a t has b e e n s e t i n t h e v o l t a g e p e ak r e g i s t er (vp k l v l[7:0]). th e v o l t a g e p e ak e v en t is r e co r d e d b y s e t t i n g t h e pkv f l ag in t h e in t e r r u p t st a t us r e g i s t er . i f t h e pkv enab le b i t is s e t t o l o g i c 1 i n t h e in t e r r u p t mas k r e g i st er , t h e ir q log i c o u t p u t wi l l g o ac ti v e lo w . simi la rl y , t h e c u r r en t p e ak e v en t is r e co r d e d b y s e t t in g t h e p k i f l ag in t h e in t e r r u p t s t a t us reg i s t er s e e t h e i n t e r r u p ts secti o n . peak level set the co n t en ts o f t h e vpkl vl and ip kl v l r e g i s t ers a r e co m p a r e d to t h e a b s o l u te va l u e o f c h a nnel 1 and c h a n nel 2, r e s p ecti v e l y , a f t e r th ey a r e m u l t i p l i ed b y 2. f o r e x a m p l e , t h e n o mi n a l ma xi m u m co de f r o m th e ch a n n e l 1 ad c wi t h a full- s c ale sig n al is 0 x 2851ecs e e t h e chann e l 1 sam p lin g s e c t ion. m u l t i p l y in g b y 2 g i v e s 0x50a3d8. th er ef o r e , wr i t in g 0x50 t o t h e i p kl vl r e g i s t er , fo r exa m ple , p u ts t h e c h anne l 1 p e ak dete c t io n le vel a t f u l l s c a l e and s e ts t h e c u r r en t p e a k dete c t io n t o i t s least s e n s i t i v e val u e . w r i t in g 0x00 p u ts t h e cha n n e l 1 dete c t io n le vel a t 0. p e a k l e vel d e te c t ion is don e b y co m p a r in g t h e co n t e n ts o f t h e ipkl vl r e g i s t er t o t h e i n comin g c hann e l 1 sa m p l e . th e ir q p i n i ndic a tes t h a t t h e p e a k le vel is exce e d e d if t h e p k i o r pkv b i ts a r e s e t in t h e in t e r r u p t enab le r e g i s t er (ir q en [15:0]) a t a d dr es s 0x0 a . peak level record the ad e7763 reco r d s th e maxim u m a b s o l u t e val u e r e ach e d b y c h a nnel 1 and c h a nnel 2 i n tw o dif f er en t r e g i st ersip ea k a n d v p eak, r e s p ecti v e l y . vp eak a n d ip eak a r e 24 -b i t , u n s i gn ed r e g i s t e r s. th e s e r e g i st e r s a r e u p da t e d e a ch t i me t h e a b s o l u t e val u e of t h e wa v e fo r m s a m p le f r o m t h e co r r es p o nding cha nne l is ab o v e t h e val u e s t o r e d i n t h e v p ea k o r ip eak r e g i s t er . th e con t e n ts o f t h e v p eak r e g i s t er co r r es p o n d t o tw o
ade7763 rev. a | page 18 of 56 t i m e s t h e max i m u m a b s o l u te v a l u e obs e r v e d on t h e c h a n nel 2 in p u t. the co n t en ts o f ip ea k rep r es en t t h e maxim u m a b s o l u t e va l u e obs e r v e d o n t h e c h annel 1 i n p u t . r e ading t h e rst v p e a k a n d r s t i p e a k r e gi s t e r s c l ea r s th ei r r e s p ecti v e co n t en t s a f t e r t h e r e ad o p era t i o n. interrupts i n ter r u p ts a r e ma na ge d t h r o u g h t h e i n ter r u p t st a t us r e g i st er (s t a tus[15:0]) a n d t h e i n t e r r u p t ena b l e r e g i st er (ir q en [15: 0]). w h en a n in t e rr u p t ev en t occurs, t h e co r r es p o n d in g f l a g in t h e s t a t us r e g i s t er is s e t t o l o g i c 1s e e t h e i n t e r r u p t s t a t us reg i st er s e c t io n. i f t h e enab le b i t fo r t h is in t e r r u p t in t h e in t e r r u p t en a b le r e g i st er is l o g i c 1, t h e ir q log i c o u t p u t wi l l g o ac t i v e lo w . the f l a g b i ts i n t h e s t a t us r e g i s t er a r e s e t ir r e s p e c t i v e o f t h e s t a t e of t h e ena b le b i t s . t o det e r m ine t h e s o ur ce o f t h e i n t e r r u p t, t h e sy s t em mas t er ( m c u ) shou l d p e r f or m a re a d f r om t h e st atu s re g i ste r w i t h r e s e t (rs t s t a t us[15:0]). this is ac hiev e d b y c a r r yin g o u t a r e ad f r o m a d dr es s 0c h. the ir q o u t p u t g o e s l o gi c h i gh a f t e r th e co m p le ti o n o f th e in t e rr u p t s t a t us r e gi s t e r r e a d co m m a n d s e e t h e i n t e r r upt t i m i ng s e c t i o n . wh e n c a r r y i ng out a re a d wi th r e s e t, t h e ad e7763 is desig n e d t o ens u r e tha t n o in t e r r u p t ev e n t s a r e m i s s e d . i f a n in t e rr u p t ev en t occur s as th e s t a t us r e g i s t er is b e in g r e ad , t h e e v en t wi l l n o t b e los t a nd t h e ir q l o gi c o u t p u t w i l l be gu a r a n t e ed t o g o h i gh f o r th e d u ra ti o n o f th e i n t e rr u p t s t a t us r e gi s t e r d a ta tra n sf e r be f o r e g o i n g logi c lo w a g a i n to i ndic a te t h e p e nding i n ter r u p t. s e e t h e n e x t s e c t ion fo r a m o r e det a i l e d des c r i p t io n. using interrupts with an m c u fi g u r e 3 8 s h ow s a t i m i n g d i a g r a m w i t h a s u g g e s t e d i m p l e - m e n t a t io n o f ad e7763 in t e r r u p t ma na g e m e n t usin g a n m c u . at t i m e t 1 , t h e ir q line g o es ac ti ve lo w , in dica t i n g t h a t on e o r m o r e i n t e r r u p t e v en ts ha ve o c c u r r e d . t i e th e ir q l o g i c output to a n e g a t i v e ed g e - t ri g g e r ed ext e r n al in t e r r u p t o n t h e mc u . c o nf igur e t h e mcu t o st a r t exe c u t in g i t s in ter r u p t s e r v ice r o u t ine (is r ) w h en a n e g a ti v e e d g e is det e c t e d o n t h e ir q lin e . af ter e n t e r i n g t h e i s r , d i s a b l e a l l i n ter r u p ts b y u s i n g t h e g l o b a l in t e r r u p t en a b le b i t . a t t h is p o in t, t h e mcu ir q ext e r n al i n te r r upt f l ag c a n b e cl e a re d to c a pt u r e i n te r r upt e v e n t s t h a t o c c u r d u r i n g t h e c u r r en t is r . w h en t h e mcu in t e r r u p t f l a g is cl e a re d, a re a d f r om t h e st a t u s r e g i ste r w i t h re s e t i s c a r r i e d out . this c a us es t h e ir q l i ne to re s e t to l o g i c h i g h ( t 2 ) s e e t h e i n ter r u p t t i mi ng s e c t io n. th e st a t us r e g i st er co n t e n ts a r e us e d t o det e r m i n e t h e s o ur ce o f t h e i n t e r r u p t(s) a n d , t h er efo r e , t h e a ppropr i a t e a c t i on to b e t a ke n . i f a su b s e q u e n t i n te r r upt e v e n t o c c u rs d u r i ng t h e is r , tha t even t wil l be r e co r d ed b y t h e m c u e x te r n a l i n te r r upt f l ag b e i n g s e t ag ai n ( t 3 ) . u p on t h e com p let i on o f th e is r , t h e g l obal in t e r r u p t mas k is c l ea r e d (s a m e in s t r u c t io n c y cle) a nd t h e ext e r n al in t e r r u p t f l ag ca us es t h e m c u t o j u m p to i t s is r a g a i n. this ens u r e s tha t t h e m c u do es n o t miss an y exter n a l in t e r r u p ts . irq global interrupt mask set isr return global interrupt mask reset clear mcu interrupt flag read status with reset (0x05) isr action (based on status contents) mcu interrupt flag set mcu program sequence 04481-a - 038 t 1 t 2 t 3 jump to isr jump to isr f i gure 37. inte rrupt man a ge ment sclk din dout irq t 11 t 11 t 9 t 1 read status register command status register contents db7 db7 db0 cs 00 0 0 01 0 1 db0 04481-a - 039 f i gure 38. inte rrupt t i mi ng
ade7763 rev. a | page 19 of 56 interrupt ti ming re vi e w t h e s e r i a l i n t e r f ace s e c t io n b e fo r e r e adi n g t h is s e c t io n. a s p r e v iou sly d e s c r i b e d, w h e n t h e ir q o u t p u t g o es lo w , t h e mcu is r wi l l r e ad t h e in t e r r u p t s t a t us r e g i s t er t o det e r m i n e t h e s o ur ce o f t h e i n ter r u p t. w h en r e adi n g t h e st a t us r e g i s t er co n t en ts, t h e ir q output i s s e t h i g h up on t h e l a st f a l l i n g e d ge of sclk o f t h e f i rst b y t e t r an sfer (r e a d i n t e r r u p t st a t us r e g i s t er co mman d ). t h e ir q o u t p u t is he ld hig h u n til the las t b i t o f t h e ne x t 1 5 - b i t t r ans f e r is shif te d ou t ( i n t e r r u p t st a t u s re g i ste r co n t en ts)s e e f i gur e 37. i f an in t e r r u p t is p e ndin g a t t h is time , th e ir q o u t p u t wil l g o lo w a g a i n. i f n o in t e r r u p t is p e ndin g , t h e ir q o u t p u t wil l s t a y hig h . temperature measurement ther e is a n on-chi p t e m p er a t ur e s e n s o r . a tem p era t ur e m e a s ur e m en t c a n b e ma de b y s e t t in g bi t 5 in t h e m o de r e g i ste r . w h en bi t 5 is s e t log i c hig h in t h e m o de r e g i st er , th e ad e7763 ini t i a t e s a t e m p era t ur e m e as ur e m e n t o f t h e n e x t zer o cr os sin g . w h en t h e zer o cr os sin g o n c h anne l 2 is det e c t e d , t h e v o l t a g e out p ut f r om t h e te m p e r a t u r e s e ns i n g c i rc u i t i s c o nne c te d to ad c1 (c ha n n el 1) fo r dig i t i z i ng. t h e r e su l t in g co de is p r o c es s e d and place d in t h e t e m p era t ur e r e g i s t e r (temp[7:0]) a p p r o x ima t e l y 26 s la ter (24 clkin/4 c y c l es). i f ena b le d in t h e in t e r r u p t ena b le r e g i s t er (bi t 5), t h e ir q output w i l l go a c t i ve lo w w h e n t h e t e m p era t ur e con v ersio n is f i nish e d . the co n t en ts o f t h e t e m p era t ur e r e g i s t er a r e sig n e d (tw o s co m p lem e n t ) wi th a r e so l u ti o n o f a p p r o x i m a t e l y 1. 5 l s b/ c . the t e m p er a t ure r e g i s t er p r o d u c es a co de o f 0x00 w h en t h e a m b i e n t t e m p era t ur e is a p p r o x i m a t e l y ?25c. the t e m p er a t ure m e as ur em en t is un c a l i b r a t ed in th e ad e7763 and mig h t ha v e a n o f fs et t o lera nce as hig h as 2 5c. analog- t o-digital conversion the a n alog-t o - dig i t a l con v ersi o n is ca r r i e d o u t usin g tw o s e co nd-o r der -? ad cs. f o r sim p lici ty , t h e b l o c k dia g ra m in fi g u r e 3 9 s h ow s a f i r s t - o r d e r - ? ad c. th e con v er t e r co m p r i s e s tw o p a r t s: th e - ? m o d u l a to r an d t h e dig i t a l lo w- pa s s f i l t e r . 24 digital low-pass filter r c analog low-pass filte r + ? v ref 1-bit dac integrator mclk/4 latched comparator .....10100101..... + ? 04481- a- 040 f i gure 39. f i rs t- o r der a -? m o d u l a to r co n v er ts t h e i n p u t sig n a l i n t o a co n t i n uo us s e r i a l st r e a m o f 1s a nd 0s a t a r a te de ter m i n e d b y t h e s a m p ling c l o c k. i n t h e ad e7763, th e s a m p lin g c l o c k is eq ual t o clki n/4. the 1- b i t d a c i n t h e fe e d b a ck l o o p is dr i v en b y t h e s e r i al da t a st re am. t h e d a c ou t p ut is su b t r a c t e d f r om t h e in p u t s i g n a l . i f t h e lo o p gain is hig h e n oug h , t h e a v era g e val u e o f t h e d a c o u t p ut (a nd t h e r efo r e t h e b i t s t re a m ) wi l l a p p r o a ch t h a t o f t h e i n p u t s i gn al lev e l . f o r a n y gi v e n in p u t val u e i n a s i n g l e sa m p l i n g in t e r v a l , t h e d a t a f r o m t h e 1 - b i t ad c is vir t ua l l y m e a n in g l ess . onl y w h en a la rg e n u m b er o f s a m p les a r e a v er ag e d can a m e a n i n gful r e sul t be ob ta in ed . t h i s a v e r a g in g is ca rri ed o u t i n th e seco n d pa r t o f th e ad c , t h e d i gi tal lo w- pa ss f i l t e r . b y a v era g in g a la rg e n u m b er o f b i t s f r o m t h e m o d u la t o r , t h e lo w- p a ss f i lte r c a n pro d u c e 2 4 - bit d a t a - w ord s t h at a r e prop or t i on a l to t h e i n put s i g n a l l e v e l. th e - ? con ver ter us es t w o t e chni q u e s t o achi e ve hi g h r e s o l u t i on f r o m w h a t is ess e n t ial l y a 1- b i t c o n v ersio n t e chniq u e . the f i rs t i s o v e r sa m p l i n g . o v e r sa m p l i n g m e a n s tha t t h e si gn al i s sa m p l e d a t a ra t e (f r e q u en c y ) tha t is man y tim e s hig h er t h a n t h e band - w i d t h o f i n t e r e st . f o r exam ple, t h e s a m p l i n g r a te i n t h e ad e 7 76 3 i s c l k i n/ 4 ( 8 94 kh z ) a n d th e ba n d o f in t e r e s t i s 40 h z t o 2 kh z . o v ers a m p lin g has t h e ef fe c t o f s p r e adi n g t h e qu a n t i za t i o n n o is e (n o i s e d u e t o s a m p lin g ) o v er a wi der b a n d wi d t h. w i t h t h e n o is e s p r e a d m o r e thinl y o v e r a wi d e r ba n d w id th , t h e q u a n ti za ti o n n o is e in t h e b a nd o f in t e r e st de c r e a s e ss e e f i g u r e 40. h o w e v e r , o v ers a m p li n g al o n e is n o t ef f i cien t e n o u g h t o i m p r o v e t h e si gn al- t o-n o ise ra ti o (s n r ) in t h e ba n d o f in t e r e s t . f o r e x a m p l e , a n o v ers a m p ling ra t i o o f 4 is r e q u ir e d j u st t o i n cr e a s e t h e snr b y 6 db (1 b i t). t o k e ep the o v ers a m p lin g r a tio a t a r e as o n a b le le v e l , i t is p o s s i b le t o s h a p e t h e qua n t i za t i on n o i s e s o t h a t t h e ma jo r i ty o f t h e n o is e l i es a t hig h er f r e q uen c ie s. i n t h e -? m o d u l a t o r , t h e n o is e is s h a p e d b y t h e in teg r a t or , w h ich has a h i gh- p a s s-t y pe r e s p o n se f o r th e q u a n ti za ti o n n o i s e . th e r e s u l t i s t h a t m o s t o f t h e n o is e is a t hig h er f r e q uen c ies, w h er e i t ca n b e r e m o v e d b y t h e dig i t a l lo w-p a ss f i l t er . this no is e sha p in g is sh ow n i n fi g u re 4 0 . 447 0 894 2 noise signal digital filter antialias filter (rc) sampling frequency high resolution output from digital lpf shaped noise 447 0 894 2 noise signal freq uency (khz) freq uency (khz) 04481-a - 041 f i gure 40. noise reduction due t o o v ersamp ling and nois e sh aping in t h e a n a l og m o du la t o r
ade7763 rev. a | page 20 of 56 antialias filter f i gur e 39 als o sh o w s a n a n alog lo w-p a s s f i l t er ( r c) o n t h e in p u t t o t h e mo d u la t o r . this f i l t er p r e v en ts a l ias i ng, w h ich is a n a r tifac t o f al l s a m p le d sys t e m s. al iasing me a n s tha t f r e q ue n c y co m p on e n ts i n t h e in p u t sig n al t o t h e ad c t h a t a r e hig h er t h a n half t h e s a m p l i ng ra t e o f t h e ad c a p p e a r in t h e s a m p le d sig n al a t a f r e q ue n c y b e lo w half t h e s a m p lin g r a t e . f i g u r e 41 il l u s t ra t e s t h e ef fe c t . f r e q uen c y co m p on e n ts (s ho wn as a r ro ws) a b o v e half t h e s a m p l i ng f r e q u e nc y ( a l s o k n o w n a s t h e n y qu i s t f r e q u e nc y , i . e ., 447 kh z) a r e ima g ed o r f o l d ed back do wn b e lo w 447 kh z. this ha p p en s wi th al l ad cs, re ga r d les s o f th e ar c h i t e c t u r e . i n t h e exa m ple sho w n, o n l y f r e q uen c ies n e a r t h e s a m p ling f r e q uen c y , i . e., 8 94 khz, m o ve i n t o t h e b a nd o f in t e r e st fo r m e t e r i ng, i . e., 4 0 h z t o 2 khz. this a l lo ws t h e us e o f a ver y sim p le lp f (lo w -p as s f i l t er) t o a t ten u a t e high f r eq uen c y (n ea r 900 kh z) no is e, and i t p r even ts dist o r tio n in t h e band o f in t e rest. f o r co n v en t i o n al c u r r en t s e n s ors, a sim p le rc f i l t er (sin g l e-p o l e l p f) wi th a co r n e r f r eq uen c y o f 1 0 kh z p r o d uc es a n a t t e n u a t i o n o f a p p r o x ima t e l y 40 db a t 894 kh z s e e f i gur e 41. the 20 db pe r decad e a t t e n u a t i o n is usual l y s u f f i cien t t o e l im ina t e t h e e f f e c t s o f a l iasin g f o r c o n v e n t i on a l c u r r e n t s e n s or s ; howe ve r , f o r a d i / d t s e ns o r s u ch as a rogo wski coil, t h e s e ns o r has a 20 db p e r de c a de ga in. t h is n e u t r a li zes t h e C20 d b p e r de ca de a t ten u a t ion pro d u c e d b y one s i m p l e lp f . ther efo r e , w h e n us ing a di / d t sen s o r , ca r e s h o u l d be tak e n t o o f f s et th e 2 0 d b pe r decad e g a in . o n e s i m p l e a p p r oa c h is t o cas c ade t w o r c f i l t ers t o p r o d uce t h e C40 db p e r de ca de a t te n u a t ion. sampling frequency image frequencies aliasing effects 0 2 447 894 freq uency (khz) 04481- a - 042 f i g u re 41. a d c a n d sig n al proc es s i ng i n chan ne l 1 o u t l i n e d i me ns io ns adc transfer function the fol l o w in g e x p r es sio n r e l a t e s t h e ou t p u t o f t h e l p f in t h e -? ad c t o t h e a n alog in p u t sig n al lev e l . b o t h ad cs in t h e ad e7763 a r e desig n e d t o p r o d uce the s a m e o u t p u t c o de f o r the sa m e i n p u t s i gnal l e v e l . ( ) 3. 04 92 2 6 2 , 1 4 4 in ou t v co de a d c v = ( 1 ) ther efo r e , wi t h a f u l l -s cal e sig n al o n t h e i n p u t o f 0.5 v a nd a n in t e r n al r e f e r e nce o f 2.42 v , t h e ad c o u t p u t c o de is n o minal l y 165,151, o r 0x2 851f . th e maxim u m c o de f r o m t h e ad c is 262,144; this is eq ui valen t t o a n in p u t sig n al le v e l o f 0.794 v . h o w e v e r , f o r s p eci f i e d pe rf o r m a n c e , d o n o t e x ceed t h e 0. 5 v f u l l -s cale in p u t sig n al le ve l . reference circu i t f i g u re 4 2 s h o w s a s i m p l i f i e d ve r s i o n of t h e re f e re nc e output cir c ui t r y . th e no minal r e fer e n c e v o l t a g e a t t h e ref in/ou t pi n i s 2.42 v . this is t h e r e fer e nce v o l t age u s e d fo r t h e ad cs . h o we v e r , c h a nne l 1 has t h r e e in pu t ra n g e o p t i o n s t h a t a r e s e le c t e d b y divi din g do w n t h e r e fer e n c e val u e us e d fo r t h e ad c i n c h a nnel 1. t h e r e fer e n c e va l u e us e d fo r c h a nnel 1 is div i de d do wn to ? an d ? o f t h e n o min a l va l u e b y using a n i n ter n a l r e sisto r di v i der , as sho w n in f i g u r e 42. 60 a pt a t 2.5v 1.7k ? 12.5k ? 12.5k ? 12.5k ? 12.5k ? ref in/out 2.42v maximum load = 10 a output impedance 6k ? reference input to adc channel 1 (range select) 2.42v, 1.21v, 0.6v 04481-a - 043 f i gure 42. r e ference ci r c u i t o u tput th e ref in /ou t p i n c a n be o v e r d r i v en b y a n e x t e rnal so u r ce s u c h a s a 2 . 5 v refere n c e. n o te t h a t t h e n o m i n a l r e fere nce v a l u e sup p l i e d t o th e ad cs is n o w 2.5 v , n o t 2 . 42 v , whic h in cr eas e s the n o minal a n alog in p u t sig n al ran g e b y 2.5/2.42 100% = 3% o r f r o m 0.5 v t o 0.5165 v . the v o l t ag e o f t h e ad e 776 3 r e fer e nce dr if ts s l ig h t l y wi t h chan g e s in t e m p era t ur e s e e t a b l e 1 fo r t h e tem p era t u r e co ef f i cien t s p e c if ic a t ion (in p p m / c). th e val u e o f t h e t e m p era t ur e dr if t va r i es f r o m p a r t t o p a r t . b e ca us e t h e r e fer e n c e i s us e d fo r t h e ad cs i n b o t h c h a nnels 1 an d 2, a n y x % dr if t i n t h e r e fer e n c e re su lt s i n 2 x % d e v i a t i o n i n t h e me te r a c c u r a c y . t h e re f e re nc e dr if t t h a t r e s u l t s f r o m a t e m p era t ur e cha n g e is u s ual l y v e r y sma l l, typic a l l y m u ch sma l l e r t h a n t h e dr if t o f ot her com p on e n ts o n a m e ter . h o w e v e r , if gua r an t e e d tem p era t ur e p e r f o r ma n c e i s ne e d e d , u s e an e x te r n a l vol t age re fe re nc e. a l te r n a t iv ely , t h e m e t e r can b e ca li b r a t e d a t m u l t i p le t e m p era t ur es. re a l -t ime co m p e n sa ti o n ca n b e a c h i ev e d ea s i l y b y us i n g t h e o n - c hi p t e m p era t ur e s e ns o r . channel 1 adc f i gur e 43 sh o w s th e ad c and sig n al p r o c es sin g c h a i n fo r c h a nnel 1. i n w a vefo r m s a m p l i n g mo de, t h e a d c o u tp u t s a sig n e d , tw os co m p le m e n t , 24-b i t da t a -w o r d a t a maxim u m o f 27.9 ks ps (cl k in/128). w i t h t h e sp ecif ie d f u l l -s cal e a n alog in p u t sig n al o f 0 . 5 v (o r 0.25 v o r 0.125 v s ee th e analog i n p u ts s e c t io n), th e ad c p r o d u c es a n o u t p u t c o de tha t is a p p r o x ima t e l y b e tw een 0x28 51 ec (+2,642,412d) a nd 0xd7 ae14 (C2,642,412d)s e e f i gur e 43.
ade7763 rev. a | page 21 of 56 1, 2, 4, 8, 16 analog input range digital integrator* hpf adc 1 reference 2.42v, 1.21v, 0.6v v1 0v 0.5v, 0.25v, 0.125v, 62.5mv, 31.3mv, 15.6mv, channel 1 (current waveform) data range active and reactive power calculation waveform sample register current rms (irms) calculation 50hz v1p v1n pga1 v1 {gain[4:3]} {gain[2:0]} *when digital integrator is enabled, full-scale output data is attenuated depending on the signal frequency because the integrator has a ? 20db/decade frequency response. when disabled, the output is not attenuated further. adc output word range 0xd 7ae4 0x0 0000 0x28 51ec 0xd 7ae4 0x00 0000 0x28 51ec channel 1 (current waveform) data range after integrator (50hz) 0xei 08c4 0x00 0000 0x1e f73c 60hz channel 1 (current waveform) data range after integrator (60hz) 0xe6 31f8 0x00 0000 0x19 ce08 04481-a - 044 dt f i g u re 43. a d c a n d sig n al proc es s i ng i n chan ne l 1 channel 1 s a mpling the w a v e fo r m s a m p les ma y b e r o u t e d t o t h e w a v e fo r m r e g i s t e r (m o d e[14:13 ] = 1, 0) f o r th e s y s t em mast er (m cu) t o r e ad . i n wa v e fo r m s a m p lin g m o de , s e t t h e w s mp b i t ( b i t 3) in t h e i n te r r upt e n abl e re g i ste r to l o g i c 1 . th e a c t i v e a nd a p p a re n t p o we r a s wel l a s t h e e n e r g y c a l c u l a t i o n re m a i n u n i n te r r upte d du r i n g w a v e f o r m s a m p l i n g . i n wa v e f o r m s a m p lin g mo de , ch o o s e on e o f f o ur o u t p u t s a m p l e ra t e s usin g b i ts 11 a nd 12 o f the m o de r e g i s t e r ( w a v s e l 1 , 0 ) . t h e o u t p u t sa m p l e ra t e c a n be 2 7 . 9 k s p s , 14 ks ps, 7 ks ps, o r 3.5 ks pss e e t h e m o de reg i ster (0x09) s e c t ion. th e in t e r r u p t re qu e s t output , ir q , sig n als a n e w s a m p le a v a i l a b i l i t y b y g o i n g ac ti v e lo w . the timin g is sh o w n in f i gur e 44. th e 24-b i t wa v e - f o r m s a m p le s a r e t r a n sfer r e d f r om t h e ad e 776 3 one b y t e ( e i g h t b i ts) a t a t i m e , wi t h t h e m o st si g n if ica n t b y t e shif t e d ou t f i rst. the 24- b i t d a t a - w o r d is r i g h t j u st if ie ds e e t h e s e r i a l i n t e r f ace s e c t io n. th e i n ter r u p t r e q u est o u t p ut ir q s t a y s lo w un til t h e i n te r r upt rout i n e re a d s t h e re s e t st atu s re g i ste r s e e t h e i n ter r u p ts s e c t i o n. channel 1 data (24 bits) read from waveform sign 0 irq sclk din dout 0 0 01 hex 04481-a - 045 f i g u re 44. w a vef o r m s a mpl i ng ch an nel 1 cha n nel 1 rms ca lcu l a t ion t h e ro ot me a n s q u a re ( r ms ) v a lu e of a c o n t i n u o u s s i g n a l v ( t ) i s def i n e d as vrm s = 0 2 ) ( 1 ( 2 ) f o r tim e s a m p lin g sig n als, t h e r m s calc u l a t ion in v o l v es s q ua r i ng t h e s i g n al , t aki ng t h e a v er a g e , and ob t a inin g t h e s q u a r e r o o t : vrm s = = 1 2 ) ( 1 ( 3 ) the ad e7763 s i m u l t an eo u s l y c a lc u l a t es t h e r m s val u es f o r c h a nnel 1 and c h a nnel 2 i n di f f er en t r e g i s t ers. f i gur e 45 sh o w s th e d e ta il o f th e si gn al p r oce s si n g c h a i n f o r th e rm s calcu l a t i o n o n c h a n ne l 1. th e c h ann e l 1 r m s val u e is p r o c es s e d f r o m t h e s a m p les us e d in th e c h a n n e l 1 wa v e f o r m s a m p lin g m o de . the c h a nne l 1 r m s val u e is st o r e d in a n u n sig n e d , 24-b i t r e g i s t er (irms). on e l s b o f t h e c h anne l 1 r m s r e g i s t er is e q ui vale n t t o 1 ls b o f a cha n ne l 1 wa v e f o r m s a m p le . the u p da t e ra t e o f t h e cha nne l 1 r m s m e as ur em en t is clki n/4.
ade7763 rev. a | page 22 of 56 irms(t) lpf3 hpf1 channel 1 0x1c 82b3 0x00 + irmsos[11:0] irms current signal (i(t)) 2 26 2 25 sgn 2 27 2 17 2 16 2 15 04481-a -046 0x28 51ec 0x00 0xd7 ae14 24 24 f i g u re 45. cha nne l 1 r m s s i g n a l pr o c e s s i ng w i t h t h e sp ec if ied f u l l -s ca le a n a l og in p u t sig n al o f 0. 5 v , t h e ad c p r o d uces a n o u t p u t co de tha t is a p p r o x ima t e l y 2,642,412d s e e t h e c h ann e l 1 ad c s e c t io n. the e q uivale n t r m s val u e o f a f u l l -s cale ac sig n al is 1,868,467 d (0x1c82b3). the c u r r en t r m s m e as ur em en t p r o v ide d in t h e ad e7763 is acc u ra t e t o wi thin 1% f o r sig n al in p u t b e tw een f u l l s c ale and f u l l s c ale/100. c o n v er t i n g t h e r e g i s t er val u e t o i t s e q u i vale n t i n a m ps m u s t b e do ne ex ter n a l ly in t h e micr o p r o cess o r usin g a n a m ps/ls b c o nst a n t . t o m i n i m i z e noi s e, s y nch r on i z e t h e r e a d i n g of t h e rm s r e gi s t e r w i th th e z e r o c r o s s i n g o f th e v o l t a g e i n p u t a n d t a k e t h e a v er a g e o f a n u m b er o f r e adi n gs. cha n nel 1 rms offset compensa tion the ad e7763 in co r p o r a t es a c h a nne l 1 r m s o f fs et co m p en s a - ti o n r e gi s t e r (i rm s o s ) . t h i s i s a 1 2 - b i t , si gn ed r e gi s t e r th a t c a n be us e d t o r e m o v e o f fs et in t h e c h a nne l 1 r m s calc u l a t io n. an o f fs et mig h t exis t i n t h e r m s c a l c u l a t ion d u e t o in p u t n o is es t h a t a r e in t e gra t e d in t h e d c co m p o n en t o f v 2 (t) . the o f fset ca lib r a t io n al lo ws t h e con t en t o f t h e irms r e g i s t er t o b e ma in tain ed a t 0 w h en n o i n p u t i s p r es en t on c h a nne l 1. on e l s b o f the cha nne l 1 r m s o f fs et is eq ui val e n t t o 32,768 ls b o f t h e s q ua r e o f t h e c h a n ne l 1 r m s r e g i s t er . a s sumin g t h a t t h e max i m u m v a l u e f r o m t h e c h annel 1 r m s c a lc u l a t ion is 1,868,467d w i th f u l l - s c a l e a c i n p u t s , th e n 1 l s b o f th e c h a n n e l 1 r m s o f fs et r e p r es en ts 0 . 46% o f t h e m e as ur e m en t er r o r a t C60 db do wn o f f u l l s c a l e . irm s = 32768 2 + ( 4 ) w h er e irm s 0 is t h e r m s m e as urem e n t w i t h o u t o f fs et co r r e c t i o n . t o m e asur e t h e o f fs et o f t h e r m s m e as ur e m en t, tw o da t a p o i n ts a r e n e e d e d f r o m n o nzer o in p u t val u es, fo r exa m ple , t h e b a s e cu rr e n t , i b , a nd i max /100. th e o f fs et can be c a lc u l a t e d f r o m t h es e me a s u r e m e n t s . channel 2 adc channel 2 s a mpling i n channe l 2 wa v e f o r m s a m p l i n g mo de (m o d e[14:13] = 1, 1 a nd w s mp = 1) , t h e ad c o u t p u t co de s c a l in g fo r c h a nnel 2 is n o t t h e s a m e as i t is fo r c h a nnel 1. the c h a n nel 2 wa vefo r m s a m p le is a 16 -b i t w o r d and sig n ex tende d to 24 b i ts . f o r n o r m a l o p era t ion, t h e dif f er en t i al v o l t ag e sig n al b e t w e e n v2p and v2 n s h o u l d n o t exce ed 0.5 v . w i th maxim u m v o l t ag e in p u t (0.5 v a t p g a g a i n of 1 ) , t h e output f r om t h e a d c s w i n g s b e t w e e n 0x2852 a n d 0x d7ae (10,322d). h o wev e r , b e f o r e bein g p a s s e d t o t h e w a v e fo r m r e g i s t er , t h e ad c o u t p u t is p a s s e d t h r o ug h a sin g le-p ole , lo w-p a s s f i l t er wi t h a c u t o f f f r eq uenc y o f 140 h z . the plo t s i n f i g u r e 46 s h o w t h e ma g n i t u d e an d phas e r e s p o n s e of t h i s f i lte r . frequency (hz) 0 10 1 10 2 10 3 ph a se ( d egrees) ?20 ?10 ?40 ?50 ?60 ?30 ?70 ?80 ?90 0 ?18 gain ( d b) 60hz, ? 0.73db 50hz, ? 0.52db 60hz, ? 23.2 50hz, ? 19.7 ?8 ?10 ?14 ?12 ?16 ?2 ?4 ?6 04481-a - 047 f i g u re 46. m a g n it u d e and p h as e r e s p ons e of lpf 1 the lp f1 has t h e ef fe c t o f a t t e n u a t ing t h e sig n al . f o r exa m ple , if t h e li n e f r e q u e n c y is 60 h z , t h e sig n al a t t h e o u t p ut o f lp f1 w i l l b e a tte n u a t e d b y ab out 8 % . | h ( f )| = 2 hz 140 hz 60 1 1 ? ? ? ? ? ? ? ? + = 0.919 = ?0.73 d b (5) n o t e l p f1 do es n o t a f f e c t t h e ac ti v e p o w e r calc u l a t ion. th e sig n al p r o c es sing c h a i n in channe l 2 is il l u s t ra ted in f i gur e 47.
ade7763 rev. a | page 23 of 56 v1 adc 2 0v analog input range 0.5v, 0.25v, 0.125v, 62.5mv, 31.25mv reference lpf1 ac t i v e a n d re ac t i v e en er g y c a l c u l a t i o n v r m s ca l c u l at i o n an d w av e f o r m sa mpl i n g (pe a k / sa g / z x ) pga2 1, 2, 4, 8, 16 {gain[7:5]} v2p v2n v2 2.42v 0x2852 0x2581 0xdae8 0xd7ae 0x0000 lpf output word range 04481-a - 048 f i g u re 47. a d c a n d sig n al proc es s i ng i n chan ne l 2 vrms[23:0] lpf3 lpf1 channel 2 0x17d338 0x00 + + vrmos[11:0] voltage signal (v(t)) 2 9 sgn 2 8 2 2 2 1 2 0 04481-a - 049 0x2518 0x0 0xdae8 f i g u re 48. cha nne l 2 r m s s i g n a l pr o c e s s i ng c h a nne l 2 has onl y o n e a n alog i n p u t ra n g e (0.5 v dif f er en t i al). l i k e cha n ne l 1, cha nne l 2 has a pga wi th gain s e lec t io n s o f 1 , 2, 4, 8, a nd 16. f o r en erg y m e asur em en t, t h e o u t p u t o f t h e ad c is p a s s e d dir e c t ly t o t h e m u l t i p li er a n d is n o t f i l t er e d . an h p f is n o t r e q u ir ed t o r e m o v e an y dc o f fs et; i t is o n l y r e q u ir ed tha t t h e o f fs et is r e m o v e d f r o m o n e channe l t o e l imina t e er r o rs ca us e d b y o f fs e t s in th e po w e r calcu l a t i o n . i n wa v e f o r m sa m p lin g m o de , o n e o f f o ur o u t p u t s a m p le ra t e s ca n be ch os en b y usin g b i ts 11 a nd 12 o f t h e mo de r e g i s t er . the a v a i lab l e o u t p u t s a m p le ra t e s a r e 27. 9 ks ps , 1 4 ks p s , 7 ks ps , o r 3. 5 ks ps s e e t h e m o d e reg i st er (0x09) s e c t io n. th e i n ter r u p t r e q u es t o u t p ut ir q indica t e s tha t a s a m p le is a v a i lab l e b y g o in g ac t i v e lo w . th e timin g is t h e s a m e as tha t f o r cha nne l 1, as sh o w n in f i gur e 44 . cha n nel 2 rms ca lcu l a t ion f i gur e 48 sh o w s t h e det a ils o f t h e sig n al p r o c es sin g c h a i n fo r t h e r m s calc u l a t ion o n c h a n ne l 2. th e c h ann e l 2 r m s val u e is p r o c es s e d f r o m t h e s a m p les us e d i n t h e c h a n nel 2 wa v e fo r m s a m p ling m o de. the r m s val u e i s s l ig h t l y a t t e n u a t e d d u e t o lp f1. th e channe l 2 r m s val u e is s t o r ed in t h e un sig n ed, 24-b i t vrms r e g i s t er . the u p da t e r a t e o f t h e c h a n ne l 2 r m s m e as ur em en t is clki n/4. w i t h t h e s p ec if ied f u l l -s c a le ac a n alog in p u t sig n al o f 0.5 v , t h e o u t p u t f r o m lpf1 swin gs between 0x2518 a nd 0xd a e8 a t 60 h z s ee t h e cha nne l 2 ad c s e c t io n. th e eq ui valen t r m s val u e o f this f u l l - s c al e ac sig n al is a p p r o x ima t e l y 1,561,400 (0x17 d338) in th e vrms r e g i st er . th e v o l t a g e r m s m e as ur e- m e n t p r o v ided in t h e ad e7763 is acc u ra t e t o wi thin 0.5 % f o r si gn al in p u t betw een full scale a nd f u l l s c ale/20. the con v ersio n f r o m th e r e g i st er val u e t o v o l t s m u s t be don e ext e r n al l y in t h e m i c r opr o c e s s or u s i n g a vo lt s / l s b c o n s t a n t . b e c a u s e t h e l o w - p a ss f i l t e r use d f o r cal c u l a t i n g t h e r m s val u e i s im p e rf ec t , t h e r e i s so me r i ppl e noi s e f r om 2 ter m p r e s en t i n t h e r m s me a s ur e m e n t. t o mi ni mi ze t h e ef fe c t o f no i s e i n t h e r e ading , s y n c hr o n i z e t h e r m s r e a d i n g w i th th e z e r o c r o s s i n g s o f th e v o l t a g e i n p u t . cha n nel 2 rms offset compensa tion the ad e7763 in co r p o r a t es a c h a nne l 2 r m s o f fs et co m p ens a t i on r e g i s t er (vrms o s). this is a 1 2 -b i t , sig n e d r e g i s t er tha t can be us e d t o r e mo v e o f fs et in t h e cha nne l 2 r m s ca lc u l a t io n . an o f fs et co u l d exist in t h e r m s ca lc u l a t ion d u e t o in p u t n o is es and dc o f fs et i n t h e in pu t s a m p les. the o f fs et cal i b r a t io n al lo ws t h e co n t en ts o f t h e v r ms r e g i s t er t o b e ma in ta in e d a t 0 when n o v o l t a g e is a p p l ie d . o n e ls b o f the cha nne l 2 r m s o f fs et is eq ui val e n t t o 1 ls b o f t h e r m s r e g i s t er . a s sumi n g t h a t t h e maxim u m v a l u e o f t h e c h a n ne l 2 r m s calc u l a t io n is 1, 561,400d wi t h f u l l -s cale ac in p u ts, t h en 1 ls b o f th e c h a n ne l 2 r m s o f fs et r e p r es en ts 0.064 % o f m e as ur em en t er r o r a t C60 db do wn o f f u l l s c a l e . vrm s = vrm s 0 + vrm s os ( 6 ) w h er e vrm s 0 is t h e r m s me as urem e n t w i t h o u t o f fs et co r r ec tio n . the v o l t a g e r m s o f fs et co m p en s a t i o n sh o u ld b e do ne b y t e s t ing t h e r m s r e s u l t s a t t w o n o nzer o in p u t le ve ls. o n e m e as ur e m en t ca n b e do ne clo s e to f u l l s c a l e and t h e o t h e r a t a p p r o x im a t ely f u l l s c ale/10. the v o l t a g e o f fs et co m p ens a t i on c a n b e der i v e d f r o m t h e s e me asur e m e n t s . i f t h e v o l t age r m s o f fs et r e g i ster do e s n o t ha v e en o u g h ra n g e , t h e ch2os r e g i s t er can als o b e us ed .
ade7763 rev. a | page 24 of 56 phase compensation w h en t h e hp f is dis a b l e d , t h e phas e er r o r b e t w e e n c h a n ne l 1 a nd cha n ne l 2 is 0 f r o m dc t o 3.5 kh z. w h en hp f is ena b led, cha nne l 1 has t h e p h as e r e s p o n s e il l u s t ra t e d in f i gur e 50 an d f i gur e 51. f i gure 52 sh o w s t h e ma g n i t u d e r e s p o n s e o f t h e f i l t er . a s s een f r o m t h e p l o t s, t h e p h as e r e s p o n s e is al m o s t 0 f r o m 45 h z t o 1 kh z, which is al l tha t is r e q u ir ed in typ i cal en erg y m e a s ur e m en t a p plica t io n s . h o w e v e r , despi t e b e in g i n t e r n a l ly p h as e-com p ens a t e d , t h e ad e7 763 m u s t w o rk wi th tra n s d u c ers, w h ich co u l d ha v e in h e r e n t phas e er r o rs. f o r exa m ple , a phas e er r o r o f 0.1 t o 0.3 is n o t u n comm on f o r a c u r r en t tra n sf o r m e r (ct). p h as e er r o rs ca n va r y f r o m p a r t t o p a r t a nd m u s t be co r r ect e d in o r der t o p e r f o r m accura t e p o w e r ca lcula t io n s . th e er r o rs as s o cia t e d w i t h phas e mi sma t ch a r e p a r t i c u l a r l y n o tic e a b le a t lo w p o w e r fac t o r s. the ad e7763 p r o v ides a m e an s o f dig i t a l l y calib r a t i n g t h es e smal l phas e er r o rs b y a l l o w i ng a s h or t t i m e d e l a y or t i me a d v a nc e to b e i n t r o d u c e d in t o t h e s i g n al pr o c es sin g cha i n t o co m p e n s a te fo r t h es e er r o rs. b e ca us e t h e co m p en sa ti o n i s in tim e , th i s t e chn i q u e s h o u ld o n l y be us e d f o r smal l p h as e er r o rs in t h e ra n g e o f 0. 1 t o 0.5. c o r r e c t i n g l a rg e phas e er r o rs usin g a t i m e s h if t t e chniq u e can in t r o d uce sig n if ica n t phas e er r o rs a t hig h er ha r m o n ic s. the phas e cal i b r a t io n r e g i st er (p h c a l [5:0]) is a tw os com p le- m e n t , sig n e d , sin g le-b yt e r e g i ster t h a t has v a l u es ra n g in g f r o m 0x21 (C31d) t o 0x1f (+31d). the reg i st er is c e n t er e d a t 0 d h, s o t h a t wr i t i n g 0 d h t o t h e reg i st e r p r o d uces 0 de l a y . by cha n g i n g t h e ph c a l r e g i s t er , t h e t i me dela y in t h e cha nne l 2 sig n al p a th ca n c h an g e f r o m C102.12 s t o +39.96 s (clkin = 3.57954 5 mh z). o n e l s b is eq ui valen t t o 2.22 s (clkin/8) time de l a y o r ad va n c e . a line f r eq uen c y o f 60 h z g i v e s a phas e r e s o l u tio n o f 0.048 a t t h e f u ndam e n t al ( i . e ., 360 2.22 s 60 h z ). f i gur e 49 il l u s t ra t e s h o w t h e p h as e co m p ens a tion is us ed t o r e mo ve a 0.1 p h as e le ad in cha n ne l 1 d u e t o t h e exter n al t r a n s d ucer . t o ca n c e l t h e le ad (0.1) i n c h an nel 1 , a ph as e l e a d m u st a l s o b e i n t r o d u c e d i n t o c h an nel 2. t h e r e so l u ti o n o f th e p h a s e a d j u s t m e n t allo w s th e i n tr o d ucti o n o f a p h as e lead in in cr em en ts o f 0.048. th e p h as e lead is achie v e d b y in t r o d uci n g a t i m e ad van c e in c h annel 2. a t i m e advanc e o f 4. 44 s i s made b y w r i t i n g ?2 ( 0 x0b ) t o t h e t i me del a y b l o c k, t h us r e d u cin g t h e am o u n t o f time de l a y b y 4.44 s, o r e q u i va le n t l y , a phas e le ad o f a p pr o x i m a t el y 0 . 1 a t l i ne f r e q u e n c y o f 60 h z . 0x0b r e p r es en ts C2 b e ca us e t h e r e g i s t er is cen t er e d wi th 0 a t 0 d h. 1 1 0 1 0 0 1 50 pga1 v1p v1n v1 adc 1 hpf 24 pga2 v2p v2n v2 adc 2 delay block 2.22 s/lsb 24 lpf2 v2 v1 60hz 0.1 v1 v2 channel 2 delay reduced by 4.44 s (0.1lead at 60hz) 0x0b in phcal [5.0] phcal[5:0] ? 102.12 s to +39.96 s 60hz 04481- a- 050 f i g u re 49. phas e cal i br at io n frequency (hz) ph a se ( d egrees) 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 ?0.1 10 2 10 3 10 4 04481-a - 051 f i g u re 50. co mbi n e d p h as e r e s p ons e of h p f and p h as e com p ens a t i on ( 10 h z to 1 k h z) frequency (hz) 0.20 40 ph a se ( d egrees) 0.18 0.16 0.14 0.12 0.10 0.08 0 0.02 0.04 0.06 45 50 55 60 65 70 04481-a - 052 f i g u re 51. co mbi n e d p h as e r e s p ons e of h p f and p h ase com p ensat i on ( 40 h z to 7 0 h z )
ade7763 rev. a | page 25 of 56 frequency (hz) 0.4 er r o r ( % ) 54 56 58 60 62 64 66 0.3 0.2 0.1 0.0 ?0.1 ?0.2 ?0.3 ?0.4 04481-a - 053 f i g u re 52. co mbi n e d g a i n r e s p o n s e of hpf a n d p h as e co mpens a t i on active power calculation p o w e r is def i n e d as t h e ra t e o f en erg y f l o w f r o m t h e s o ur c e t o t h e lo ad . i t is de f i n e d as t h e p r o d uc t o f t h e v o l t a g e an d c u r r e n t wa v e fo r m s. the r e su l t in g w a v e fo r m is ca l l e d t h e in st a n t a ne o u s p o w e r sig n al and is eq u a l t o t h e ra t e o f energ y f l o w a t an y g i v e n tim e . the uni t of p o w e r is t h e wa t t o r jo u l es /s. e q ua t i o n 9 g i v e s a n ex p r ession for t h e inst an t a ne o u s p o w e r sig n a l in an ac syst e m . ) sin( 2 ) ( t v t v = ( 7 ) ) sin( 2 ) ( t i t i = ( 8 ) w h er e: v is t h e r m s v o lt a g e . i i s th e rm s cu rr e n t . ) ( ) ( ) ( t i t v t p = ) 2 cos( ) ( t vi vi t p ? = (9) the a v er a g e p o w e r o v er a n i n t e g r al n u m b er o f line c y cles (n) is g i v e n b y t h e ex p r es sio n in e q u a tio n 10. = = nt vi dt t p nt p 0 ) ( 1 (10) w h er e: t is t h e li ne c y cl e p e r i o d . p is th e ac t i v e or r e al p o w e r . n o t e t h a t the ac ti v e p o wer is eq ual t o t h e dc com p on en t o f t h e in s t an t a n e o u s p o w e r sig n al p ( t ) in e q ua t i o n 8, i.e ., vi . this is th e re l a tio n s h i p us ed t o calc u l a t e ac ti v e p o w e r in t h e ad e7763. the ins t an t a n e ous p o w e r sig n al p ( t ) is gen e ra t e d b y m u l t i p ly ing t h e c u r r e n t and v o l t age si g n als. the dc com p onen t of t h e i n s t an- t a n e o u s p o w e r sig n al is t h e n ext r ac t e d b y lp f2 (lo w-p as s f i l t er) t o ob ta in t h e act i v e po w e r in f o r m a t io n. th i s p r oces s i s il l u stra t e d in f i gur e 53. instantaneous power signal p(t) = v i-v i cos(2 t) ac t i v e re al p o w e r si g n a l = v i 0x19 999a vi 0xc cccd 0x0 0000 04481-a - 054 current i(t) = 2 i sin( t) voltage v(t) = 2 v sin( t) f i gure 53. ac tive p o w e r cal c ul ati o n b e ca us e lp f2 do es n o t ha v e an ide a l b r i ck wal l f r e q uen c y r e s p o n s e (s e e f i gur e 54), th e ac t i v e p o w e r sig n al has s o me r i p p le d u e t o t h e in st a n t a ne o u s p o w e r sig n al . this r i p p le is s i n u so id al a n d h a s a f r eq ue n c y eq ual t o tw i c e t h e lin e f r eq ue n c y . b e ca us e t h e r i p p le is sin u so ida l in n a t u r e , i t is r e m o v e d w h en t h e a c ti v e p o w e r s i g n al i s i n t e gra t ed t o cal c ula t e en er g y see th e en erg y c a lc u l a t io n s e c t io n. frequency (hz) ?2 4 1 db ?2 0 3 1 0 3 0 100 ?1 2 ?1 6 ?8 ?4 0 04481-a - 055 fi g u r e 5 4 . fr e q u e n c y r e s p o n s e o f l p f 2
ade7763 rev. a | page 26 of 56 apos[15:0] wgain[11:0] wdiv[7:0] lpf2 current channel voltage channel output lpf2 time (nt) 4 clkin t act i v e p o w e r si g n a l + + aenergy[23:0] o u tp u t s f r o m t h e lp f2 a r e a c c u m u la te d ( in te gr a t e d ) i n t h e i n t e r na l a c t i v e e ne rg y r e g i s t e r u ppe r 2 4 b i t s a r e ac ce s s i b l e t h ro u g h ae ne rg y [ 23: 0] re g i s t e r 23 0 48 0 wav e f o r m re g i s t e r va l u e s 04481-a - 056 % f i gure 5 5 . a c ti v e en er gy c a l c u l a t i o n f i gur e 55 sh o w s th e s i g n al p r o c es sin g c h a i n f o r th e ac ti v e p o w e r calc u l a t io n. th e ac ti v e p o w e r is calc u l a t e d b y lo w-p as s f i l t er in g t h e in st a n t a n e ous p o w e r sig n al . n o t e t h a t w h en r e adin g t h e w a ve f o r m s a m p l e s f r om t h e output of l p f 2 , t h e g a i n of t h e ac t i v e e n erg y can b e ad j u st e d b y usin g t h e m u l t i p lier an d wa t t ga in r e g i s t er (w gain[11:0]). th e ga in is ad j u s t ed b y wr i t in g a tw os co m p lem e n t 12-b i t w o r d to th e wa t t ga in r e g i s t er . e q ua tion 11 sh o w s h o w t h e gain ad j u s t m e n t is r e l a t e d t o t h e co n t en ts o f t h e wa t t ga in r e g i s t er : ? ? ? ? ? ? ? ? ? ? ? ? ? ? + = wgain power active wgain output (11) f o r exa m p l e , w h en 0x7ff is wr i t t e n t o the wa t t ga in r e g i s t er , the p o w e r o u t p u t is s c al e d u p b y 50 %. 0x7 ff = 204 7d, 2 047 /2 12 = 0. 5. s i mi la rl y , 0x800 = C2048d (sig ned tw os co m p lem e n t ) an d p o w e r o u t p u t is s c ale d b y C50%. e a c h ls b s c ales th e p o w e r o u t p u t b y 0.024 4%. f i gur e 56 sh o w s t h e max i m u m c o de (h exade c imal) ou t p ut ra n g e fo r t h e ac t i v e p o w e r sig n al (lp f 2). n o t e t h a t t h e ou t p ut ra n g e chan g e s dep e ndi n g o n t h e co n t en ts o f t h e w a t t ga i n r e g i s t er . th e mi nim u m o u t p ut ra n g e is g i v e n when t h e wa t t g a in r e g i st er co n t en ts a r e eq ual to 0x800, a n d t h e max i m u m r a n g e is g i ven b y wr i t in g 0x 7f f to t h e wa t t ga i n r e g i s t er . this can b e us e d t o cal i b r a t e t h e ac t i ve p o w e r (o r en erg y ) calc u l a t io n. 0x1 3333 0xcccd 0x6666 0xf 999a 0xf 3333 0xe cccd 0x0 0000 activ e p o we r outp ut positive power negative power 0x000 0x7ff 0x800 { w g a i n [ 11: 0] } active power calibration range 04481-a - 057 f i gure 56. ac tive p o w e r cal c ul ati o n o u tput range energy calculation a s s t a t e d ea rl ier , p o w e r is def i ned as t h e ra t e o f en erg y f l o w . this r e la t i o n shi p is exp r e s s e d ma th ema t ica l ly in eq ua t i o n 12. dt de p = ( 1 2 ) w h er e: p is p o w e r . e is e n erg y . c o n v ers e ly , en erg y is g i v e n as th e in t e g r al o f p o w e r . = pdt e ( 1 3 )
ade7763 rev. a | page 27 of 56 fo r w av e f o r m a c c u m u la tion 1 24 24 lpf2 v i 0x1 9999 0x19 999a 0x00 0000 instantaneous power signal ? p(t) fo r w av e f 0rm sa m p l i n g 32 0xc cccd current signal ? i(t) hpf v o l t a g e s i g n a l ? v(t) mul tiplier + + apos[15:0] 2 6 sgn 2 5 2 -6 2 -7 2 -8 04481-a - 058 wgain[11:0] f i g u re 57. ac t i ve p o wer s i g n al proc es s i ng the ad e7763 ac hiev es t h e in t e g r a t io n o f t h e ac ti v e p o w e r sig n al b y con t in uo us l y acc u m u l a tin g t h e ac ti ve p o w e r sig n al in a n in t e r n al u n r e adab le 49-b i t energ y r e g i s t er . th e ac t i v e en erg y r e g i s t er (aene r gy[23:0]) r e p r es en ts t h e u p p e r 24 b i ts o f this in t e r n al r e g i s t er . this dis c r e t e t i m e acc u m u la t i o n o r s u mma tio n is eq ui valen t t o in teg r a t ion in c o n t in uo us tim e . e q ua tion 14 exp r es s e s t h is r e la t i on s h i p . 0 1 () ( ) t n e p t dt li m p nt t = ?? == ? ? ? ? ( 1 4 ) w h er e: n i s th e d i scr e t e tim e sa m p le n u m b e r . t is t h e s a m p le p e r i o d . t h e d i sc r e t e tim e sa m p l e p e ri od ( t ) f o r th e accum u la ti o n r e g i s t er is 1.1 s (4/clki n ). i n addi tion t o calc u l a t in g t h e en erg y , t h is in t e g r a t io n r e m o v e s a n y sin u s o i d a l co m p on e n ts th a t mi g h t be in th e a c ti v e po w e r s i gn al . f i gur e 57 sh o w s this dis c r e t e tim e in t e g r a t io n, o r acc u m u l a tion. the ac t i ve p o w e r sig n al i n t h e w a vefo r m reg i st er is con t i n u o usl y adde d t o t h e in ter n al ac ti v e en erg y r e g i s t er . this addi tion is a sig n e d addi t i o n ; t h er efo r e , nega t i v e e n erg y is s u b t rac t e d f r o m t h e ac t i v e e n erg y co n t en ts. th e excep t io n t o t h i s is w h en p o a m is s e lec t e d in t h e m o d e [15:0] r e g i s t er , in which cas e o n l y p o si t i v e e n erg y co n t r i b u t e s t o t h e ac t i v e e n erg y acc u m u l a t i on s e e t h e p o si t i ve- o nl y a c c u m u la t i o n m o de s e c t i o n. the o u t p u t o f t h e m u l t i p l i er is divide d b y wd i v . i f t h e v a l u e i n th e wd iv r e g i st er is eq ual t o 0, th en t h e in t e r n al ac ti v e en erg y r e g i s t er is divided b y 1. wd iv is a n 8-b i t, un sig n e d r e g i s t er . af t e r divid i n g b y wdiv , t h e ac t i ve e n erg y is acc u m u l a t e d i n a 49-b i t in t e r n al en erg y acc u m u la tio n r e g i s t er . the u p p e r 24 b i ts o f t h is r e g i s t er ar e acces s ib le t h ro ug h a r e ad t o t h e ac t i v e e n erg y r e g i s t er (aene r gy[23:0]). a r e ad t o t h e r a e n er gy r e g i st er r e t u r n s t h e con t en t o f t h e ae ner g y r e g i s t er , a nd t h e u p p e r 24 b i t s o f t h e i n ter n al reg i st er a r e cl e a re d . a s sho w n i n fi g u re 5 7 , th e ac ti v e p o w e r sig n al is acc u m u l a t e d in a n in t e r n al 49 -b i t , s i gn ed r e gi s t e r . t h e a c ti v e po w e r s i gn al c a n be r e a d f r o m th e wa v e f o r m r e g i s t er b y s e t t in g m o d e [14:13] = 0 , 0 a nd s e t t in g th e w s mp b i t (b i t 3) in the in ter r u p t ena b le r e g i s t er t o 1. l i k e c h a nnel 1 and c h a nnel 2 wa ve fo r m s a m p lin g m o des, t h e wa v e f o r m da ta is a v a i la b l e a t s a m p le ra t e s o f 27 .9 ks ps, 14 ks p s , 7 ks ps, o r 3.5 ks pss ee f i gur e 44. f i gur e 58 sh o w s this energ y acc u m u l a tio n f o r f u l l -s cale s i g n als (sin us o i dal) o n t h e analog in p u ts. th e t h r e e c u r v es i l l u s t ra t e t h e mi ni m u m t i me fo r t h e e n erg y re g i st er t o r o l l o v e r w h e n t h e ac t i ve p o w e r ga in reg i s t er co n t en ts a r e 0x7ff , 0x000, a nd 0x800. th e wa t t ga in r e g i s t er is us ed t o ca r r y o u t p o w e r ca li b r a t io n. a s s h o w n , th e f a s t e s t i n t e gr a t i o n ti m e oc cu r s wh e n th e w a t t g a i n r e g i s t er is s e t t o maxim u m f u l l s c ale , i.e ., 0x7ff . 0x00 0000 0x7f ffff 0x3f ffff 0x40 0000 0x80 0000 aenergy[23:0] 6.2 48 12.5 time (minutes) wgain = 0x7ff wgain = 0x000 wgain = 0x800 04481-a - 059 f i gure 5 8 . ener gy r e gi st er rol l o v er t i m e f o r f u ll -s c a l e p o w e r ( m ini m u m and m a x i mum p o wer g a in ) n o t e t h a t t h e e n erg y r e g i s t er co n t e n ts r o l l o v er t o f u l l -s cale n e g a ti v e (0x80 0000) a n d con t in ue in cr easin g in val u e w h en t h e p o w e r o r en erg y f l o w is p o si ti v e s ee f i gur e 58. c o n v ers e ly , if t h e p o w e r was n e g a t i v e , t h e e n erg y r e g i s t er w o u l d under f lo w to f u ll-scale posi tiv e (0x7f ffff) a n d co n t in ue d e cr easin g in va l u e . b y usin g th e in ter r u p t ena b le r e g i s t er , t h e ad e 7763 ca n be co nf igur e d t o issue a n in ter r u p t ( ir q ) w h e n th e a c ti v e e n e r g y r e g i s t er is m o r e tha n half f u l l (p osi t i v e o r nega tiv e ), o r wh en a n ov e r f l ow o r u n d e r f l o w o c c u r s .
ade7763 rev. a | page 28 of 56 integr ation ti me un de r st e a d y loa d a s m e n t ion e d i n t h e la st s e c t ion, t h e dis c r e te t i m e s a m p le pe ri od ( t ) f o r th e ac c u m u la t i o n r e g i s t er is 1.1 s (4/clki n ). w i t h f u l l -s cale sin u s o idal sig n a l s o n t h e analog in p u ts an d t h e w g ai n r e g i st er s e t t o 0x000, t h e a v era g e w o r d val u e f r o m each lp f2 is 0xc cc cds ee f i gur e 53. the maxim u m p o si ti ve val u e tha t can b e s t o r ed in t h e in t e r n al 49 -b i t r e g i s t er bef o r e i t ov e r f l ow s i s 2 48 , o r 0xfff f ff f f fff f . t h e in tegra t io n t i m e un der th es e condi tion s wi t h wd iv = 0 is calc u l a t e d as f o l l o w s: ti m e = min 26 . 6 s 8 . 375 s 12 . 1 cccd 0xc ffff ffff 0xffff = = (15) w h en wd iv is s e t t o a val u e o t h e r t h an 0, t h e i n t e g r a t io n t i m e va r i es, as sh o w n in e q ua tio n 16. ti m e = ti m e wd i v = 0 wd iv (16) power offset calibration the ad e7763 in co r p o r a t es an ac ti v e p o w e r o f fs et r e g i st er (apos[15:0]). this is a sig n e d , tw os co m p lem e n t , 16 -b i t r e gis t er tha t can be use d t o r e m o v e o f fsets in the ac ti v e p o w e r calc u l a t io n s e e f i gur e 57. an o f fs et co u l d exist in t h e p o w e r calc u l a t io n d u e t o cr os s t al k betw een c h a n ne ls o n t h e pcb o r in t h e ic i t s e lf. the o f fs et cal i b r a t i o n al lo ws t h e con t e n ts o f t h e ac ti v e p o w e r r e gis t er t o be m a in ta in e d a t 0 w h en n o p o w e r is be in g co n s um e d . the 256 ls bs ( a pos = 0x0100) wr i t t e n t o t h e ac ti v e p o w e r o f fs et r e g i st er a r e e q ui v a len t t o 1 ls b in t h e wa v e fo r m s a m p le r e g i st er . a ssumi n g t h e a v era g e v a l u e o u t p u t f r o m lp f2 is 0xc cccd (83 8 ,861d) w h en in p u ts on cha n ne ls 1 a n d 2 a r e bo t h a t f u l l s c al e . a t ?60 db do wn o n cha n ne l 1 (1/1000 o f th e c h a nne l 1 f u l l -s cale i n p u t), t h e a v era g e w o r d va l u e o u t p u t f r o m lp f2 is 838.861 (838,861/1,000). on e ls b in t h e lp f2 o u t p u t has a m e as ur em en t er r o r o f 1/838.861 100% = 0.119% o f the a v era g e val u e . th e ac t i v e p o w e r o f fs et r e g i st er has a r e s o l u t i o n eq ual t o 1/256 ls b o f th e wa v e fo r m r e g i s t er ; t h er efo r e , th e p o w e r o f fs et co r r ec tio n r e s o l u tio n is 0.00047%/ls b (0.119% /256) a t C60 db . energy-to-freque nc y con v ersio n the ad e7763 p r o v ides energ y -t o-f r eq uen c y co n v ersio n fo r ca l i b r a t io n p u r p os es. af t e r ini t ia l ca l i b r a t io n a t ma n u fac t ur i n g, t h e ma n u fa c t u r er o r en d cus t o m e r o f t e n v e r i f i e s t h e en e r g y m e t e r cal i b r a t io n. one co n v enien t wa y t o v e r i f y th e m e t e r cal i b r a t io n is fo r t h e ma n u f a c t ur er t o p r o v i d e a n o u t p u t f r e q uen c y , which is prop or t i on a l to t h e e n e r g y or a c t i ve p o w e r u n d e r ste a dy l o a d co ndi t io n s . t h is o u t p u t f r eq uen c y ca n p r o v ide a sim p le , s i n g le- wi r e , o p ticall y i s o l a t ed in t e rfa c e t o ext e rnal cali b r a t i o n eq ui p- m e n t . f i gur e 59 i l l u st ra t e s t h e e n erg y -t o-f r e q ue n c y co n v ersio n . cfnum[11:0] cf 11 0 cfden[11:0] 11 0 aenergy[48:0] 4 80 04481-a - 060 % dfc f i gure 5 9 . ener gy -to - f r equenc y c o n v ersi o n a di g i t a l - to - f re qu e n c y c o n v e r te r ( d f c ) i s u s e d to ge ne r a te t h e cf p u ls e d o u t p u t . th e d f c ge n e ra t e s a p u ls e e a ch t i me 1 ls b in t h e ac ti v e en er g y r e gis t er is acc u m u la t e d . an o u t p u t p u lse is g e n e ra t e d w h en (cfd en + 1)/(cfnu m + 1) n u m b er o f p u ls es a r e g e n e ra t e d a t t h e d f c o u t p u t . u n der st e a d y lo ad co ndi t io n s , t h e o u tput f r e q u e nc y i s prop or t i on a l to t h e a c t i ve p o we r . the max i m u m o u t p ut f r e q uenc y , w i t h ac in p u t sig n a l s a t f u l l s c ale , cfnu m = 0x00, a n d cf d e n = 0x00, is a p p r o x ima t e l y 23 kh z. ther e a r e tw o u n sig n e d , 12 -b i t r e g i st ers, cfnu m[11:0] a n d c f d e n [ 11 :0 ], th a t c a n be u s ed t o set th e c f f r eq u e n c y t o a wid e ra n g e o f val u es. th e s e f r e q ue n c y-s c al in g r e g i st e r s a r e 12-b i t r e g i st ers t h a t can s c ale t h e o u t p u t f r e q uen c y b y 1/2 12 t o 1 wi t h a step of 1 / 2 12 . i f t h e val u e 0 is wr i t t e n t o an y o f t h es e r e g i st ers, t h e val u e 1 wi l l b e a p pl ie d t o t h e r e g i st er . the r a t i o ( c f n u m + 1 ) /( cfd e n + 1) s h o u ld be s m alle r th a n 1 t o e n s u r e p r o p e r o p e r a t i o n . i f t h e r a t i o o f t h e r e gist er s (cfnu m + 1)/(cfd e n + 1) i s g r e a t e r t h a n 1 , t h e r e g i st er val u es wi l l b e ad j u st e d t o a ra t i o (cfnu m + 1)/ (cfd en + 1) o f 1. f o r exa m p l e , if the o u t p u t f r eq uen c y is 1.562 kh z while th e con t en ts o f cfd e n a r e 0 (0x000), th en the o u t p u t f r eq uen c y ca n be s e t t o 6 . 1 h z b y wr i t in g 0xff t o th e cfd e n r e g i st er . w h en cfnu m a n d cfd e n a r e b o t h s e t t o o n e , t h e cf p u ls e wid t h is f i xed a t 16 clki n/4 c l o c k c y c l es, a p p r o x im a t e l y 18 s wi t h a clki n of 3. 579 545 mh z. i f t h e cf p u l s e o u t p u t is lon g er tha n 180 m s fo r a n ac ti ve en erg y f r eq uen c y o f l e s s tha n 5.56 h z , t h e p u ls e wi d t h is f i xe d a t 90 m s . o t h e r w is e , t h e p u ls e wi d t h is 50% o f the d u ty c y c l e . the o u t p u t f r e q uen c y has a sl ig h t r i p p le a t a f r e q uen c y e q u a l to t w ice t h e li n e f r e q uen c y . this is d u e t o i m p e r f e c t f i l t er in g o f t h e i n s t an t a ne ou s p o we r s i g n a l to g e ne r a te t h e ac t i v e p o we r s i g n a l s e e th e a c ti v e p o w e r c a l c ul a t i o n s e ct i o n . eq u a ti o n 8 g i v e s a n exp r essio n fo r t h e in st a n t a n e o u s p o w e r sig n al. this is f i l t er e d b y lpf2, w h ich ha s a ma g n it ude resp o n s e g i ven b y e q ua t i on 17. 2 9 . 8 1 1 ) ( 2 f f h + = ( 1 7 )
ade7763 rev. a | page 29 of 56 t h e acti ve po w e r sign al (o u t p u t o f lp f2) ca n b e r e w r i t t e n as ) 4 cos( 9 . 8 2 1 ) ( 2 t f f vi vi t p l l ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? + ? = ( 1 8 ) wher e f l i s t h e l i ne f r e q u e nc y , f o r e x am pl e, 6 0 hz . f r om e q u a t i on 1 3 , ) 4 sin( 9 . 8 2 1 4 ) ( 2 t f f f vi vit t e l l l ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? + ? = (19) n o t e t h a t in e q ua t i on 19 t h er e is a smal l r i p p le in t h e e n erg y calc u l a t io n d u e t o a sin(2t) co m p o n en t. t h is is s h o w n g r a p hi- cal l y in f i gur e 6 0 . the ac t i ve e n erg y calc u l a t ion is r e p r es en t e d b y t h e d a sh e d , stra igh t l i n e an d is eq ual t o v i t. th e sin u - s o idal r i p p le in th e ac ti v e energ y calc u l a t io n is als o s h o w n. b e ca us e t h e a v e r a g e val u e o f a sin u s o i d is 0, t h e r i p p le do es n o t co n t r i b u te t o t h e en erg y calc u l a t io n o v er t i me . h o w e v e r , t h e ri p p le m i g h t be o b se r v ed in t h e f r eq u e n c y o u t p u t , e s peciall y a t hig h er o u t p u t f r eq uen c ies. th e r i p p le beco m e s la rg er as a p e r c en t a g e o f t h e f r e q uen c y a t l a rg er lo ads a n d hig h er o u t p u t f r e q uen c ies. thi s o c c u rs b e ca us e t h e i n t e g r a t ion o r a v era g in g t i m e i n t h e e n erg y -t o-f r e q uen c y co n v ersio n p r o c ess is sh o r t e r a t h i g h e r output f r e q u e nc i e s . c o ns e q u e n t ly , s o me of t h e s i n u s o i d a l ri p p l e in t h e en er g y si g n al is obs e r v a b le in t h e f r eq uen c y o u t p u t . ch o o sin g a lo wer o u t p u t f r eq uen c y a t cf f o r cali b r a t io n ca n sig n if ican t l y r e d u ce t h e r i p p le . als o , a v era g in g t h e ou t p u t f r e q uen c y b y usin g a lo n g er ga te t i m e fo r t h e c o un t e r ac hie v es th e s a m e r e s u l t s. vi sin(4 04481-0-061 f i g u re 60. o u t p ut f r equ e nc y r i p p le 04481-a - 062 wdiv[7:0] apos[15:0] wgain[11:0] lpf1 + + laenergy[23:0] accumulate active energy in internal register and update the laenergy register at the end of linecyc line cycles output from lpf2 from channel 2 adc 23 0 linecyc[15:0] 48 0 % zero crossing detection calibration control f i gure 6 1 . ener gy ca lcula t io n l i ne c y cl e ener gy a c cu m u la ti on mo d e
ade7763 rev. a | page 30 of 56 line cycle energy accumulation mode i n lin e c y c l e en er g y a ccum u la ti o n m o de , th e en er g y a ccum u - l a ti o n o f t h e ade7763 ca n be sy n c hr o n ize d t o t h e chann e l 2 zer o cr os sin g so tha t ac t i v e en erg y acc u m u l a t e s o v er a n in t e gral n u m b e r o f h a lf lin e c y c l es. th e ad va n t a g e o f s u mm in g t h e a c t i v e en erg y o v er a n i n t e g r al n u m b er o f lin e c y cles is t h a t t h e sin u so id al co m p o n en t in t h e ac ti v e en er g y is r e d u ced t o 0. t h is e l imina t es r i p p l e in t h e e n erg y ca lc u l a t io n. ene r g y is ca lc u l a t e d mo r e ac c u r a tely and i n a sh o r ter t i me b e c a us e t h e i n teg r a t ion pe r i o d i s s h o r t e n e d . b y u s i n g th e lin e c y c l e en e r g y a ccum u la ti o n m o de , t h e energ y calib r a t ion c a n b e g r e a t l y si m p lif i e d , an d t h e tim e r e q u i r ed t o cali b r a t e th e m e t e r ca n be si g n i f ic a n tl y r e d u ced . the ad e7763 is p l aced in l i n e c y c l e en erg y acc u m u l a tio n m o de b y s e t t i n g b i t 7 (cy c m o d e ) in t h e m o de r e g i st er . i n li n e c y cle en erg y acc u m u l a tio n m o de , t h e ad e7763 acc u m u l a t e s t h e ac t i v e p o w e r sig n al in t h e l a e n er gy r e g i st er (a ddr es s 0x04) f o r a n in t e gral n u m b er o f lin e c y c l es, as s h o w n in f i gur e 61. the n u m b er o f half line c y cles is sp e c if ie d i n t h e li necy c r e g i st er (a ddr es s 0x1c) . the ad e7763 ca n acc u m u la te ac ti v e p o w e r fo r u p t o 65,535 hal f line c y c l es. b e ca us e t h e ac ti ve p o w e r is in tegra t e d o n an in t e gral n u m b er o f lin e c y c l es, th e cy ce n d f l a g in t h e in ter r u p t s t a t us r e gist er is set (b i t 2) a t t h e en d o f a line c y cle en erg y acc u m u l a t i o n c y cle . i f t h e c y cend ena b le b i t in t h e in t e r r u p t ena b le r e g i st er is ena b le d, t h e ir q output a l s o wi l l g o ac t i ve lo w . th er efo r e , t h e ir q lin e can als o be us e d t o sig n al t h e com p let i o n o f t h e li ne c y cle en erg y acc u m u l a t i on. an o t h e r c a lib r a t io n c y c l e ca n s t a r t as lo n g as the cy cm o d e b i t in t h e m o de r e gis t er is set. f r o m e q ua tio n s 13 a n d 18, ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? + ? = nt nt dt t f f vi dt vi t e 0 2 0 ) 2 cos( 9 . 8 1 ) ( (20) wher e: n is a n in teg e r . t is t h e lin e c y c l e p e r i o d . since t h e si n u s o idal co m p o n en t is in teg r a t e d o v er a n in t e g r al n u m b er o f li n e c y cles, i t s val u e is alwa ys 0. th e r efo r e , + = nt vidt e 0 0 ( 2 1 ) () e tv i n t = ( 2 2 ) n o t e th a t i n th i s m o d e , th e 1 6 - b i t l i n e c y c r e g i s t e r c a n h o l d a m a xim u m val u e o f 65,535. i n oth e r w o r d s, t h e line en erg y acc u m u la tio n m o d e can be us ed t o acc u m u l a te ac ti v e en er g y f o r a m a xim u m d u r a tio n o f 65,535 half lin e c y c l es. a t 60 h z l i n e f r eq uen c y , this t r a n s l a t es t o a t o tal d u r a tio n o f 6 5 ,535/ 120 h z = 546 s e co n d s. posi tive- o nly accum u latio n m o de i n po s i ti v e - o nl y a c cu m u la ti o n m o d e , th e e n e r g y a c cu m u la ti o n i s on ly d o ne f o r p o s i t i ve p o we r , i g nor i ng a n y o c c u r r e n c e of n e ga ti v e po w e r a b o v e o r be lo w th e n o - l oad th r e s h o l d , a s s h o w n in f i gur e 62. the cf p u lse also r e f l ec ts this acc u m u l a tio n m e th od wh e n in th i s m o d e . p o s i ti v e - o nl y a c cum u la ti o n m o d e i s ac t i va t e d b y s e t t in g t h e ms b o f t h e mo de r e g i ster (m o d e[15]). the def a u l t s e t t i n g fo r t h is m o de is o f f. t r a n si t i o n s in t h e d i re c t i o n of p o we r f l o w , goi n g f r om ne g a t i ve t o p o s i t i ve or pos i ti v e t o n e ga ti v e , set t h e ir q p i n t o a c ti v e lo w i f th e p p o s a n d pneg b i ts a r e s e t i n t h e in ter r u p t ena b le r e g i st er . th e c o r r e s p o nd i n g pp os and pne g b i t s i n t h e i n t e r r u p t st a t u s r e gi s t e r s h o w wh i c h tra n si ti o n h a s occu rr ed s ee th e r e gi s t e r des c r i p t io n s i n t a b l e 9. pneg ppos ppos interrupt status registers ppos pneg pneg irq no-load threshold active power no-load threshold a ctive energ y 04481-a - 063 f i gure 62. e n er gy ac cu m u l a ti on in p o s i tive - o nly ac cu mul a tio n mod e no-loa d t h reshold the ad e7763 in c l udes a n o -lo a d thr e sh old fea t ur e o n t h e ac t i v e e n erg y t h a t e l imina t es an y cr e e p ef fe c t s i n t h e m e t e r . thi s is acco m p lish e d b e c a us e e n erg y do es n o t acc u m u l a t e if t h e m u l t i p lier o u t p u t is b e lo w t h e n o -lo a d t h r e sh o l d . t h is thr e sh o l d is 0.001% o f the f u l l -s cale o u t p u t f r eq uen c y o f th e m u l t i p l i er . c o m p a r e this val u e t o t h e iec1 036 s p ecif ic a t ion, whic h s t a t es tha t t h e m e t e r m u s t s t a r t u p wi th a lo ad e q ual to o r les s tha n 0.4% i b . this standa r d tran sla t es t o 0.0167% o f t h e f u l l -s cale output f r e q u e nc y of t h e m u lt ipl i e r .
ade7763 rev. a | page 31 of 56 apparent power calculation the a p p a r e n t p o w e r is t h e max i m u m p o w e r t h a t can b e deliver e d to a lo ad . v rm s an d i rm s a r e t h e ef fe c t i v e v o l t a g e an d c u r r en t de li v e r e d t o t h e lo ad; t h e a p p a r e n t p o wer (ap) is def i n e d as v rm s i rm s . th e a n gle be tw ee n th e acti v e po w e r a n d t h e a p p a r e n t p o w e r g e n e ral l y r e p r es en ts t h e phas e shif t d u e t o n o nr esist i ve lo ads. f o r sin g le-phas e a p pl ic a t io ns, r e p r es en ts t h e an g l e b e tw e e n t h e v o l t a g e and t h e c u r r en t s i g n alss e e f i g u re 6 3 . e q u a t i on 2 4 g i ve s a n e x pre s s i on of t h e i n s t an t a n e ou s p o w e r sig n a l in a n ac sy ste m w i t h a phas e sh if t. re ac t i v e po wer ap p a re nt p o w e r a c t i ve po wer 04481-a - 064 f i gure 63. p o wer t r iangle () 2 s i n ( ) rm s vt v t = () 2 s i n ( ) rm s it i t = + ( 2 3 ) ) ( ) ( ) ( t i t v t p = ) 2 cos( ) cos( ) ( + ? = t i v i v t p rms rms rms rms (24) the a p p a r e n t p o w e r is def i n e d as v rm s i rm s . this exp r essio n is inde p e n d e n t f r o m t h e phas e a n g l e b e tw e e n t h e c u r r en t an d th e v o l t a g e . f i gur e 64 i l l u st ra t e s t h e sig n al pr o c essin g i n e a ch phas e fo r t h e calc u l a t io n o f t h e a p p a r e n t p o w e r in t h e ad e 7763. v rms i rms 0xa d055 a p p a re nt p o w e r si g n a l ( p ) current rms signal ? i(t) v o l t a g e r m s s i g n a l ? v(t) multiplier 04481-a - 065 0x00 0x1c 82b3 0x00 0x17 d338 vagain f i gure 64. a p pa r e n t p o w e r s i gna l pr o ces s i ng the ga i n o f t h e a p p a r e n t e n erg y ca n b e ad j u st e d b y usin g t h e m u l t i p li er a n d v a gain r e g i ster (v a g ain[11:0]). th e ga i n is ad j u ste d b y wr i t in g a tw os co m p lem e n t , 12- b i t w o r d to t h e v a gain r e g i ster . e q ua t i on 25 s h o w s h o w t h e ga in ad j u s t m e n t is r e la t e d t o t h e co n t e n ts o f t h e v a gain r e g i ster . ? ? ? ? ? ? ? ? ? ? ? ? ? ? + = vagain power apparent in outputvaga (25) f o r ex am pl e , w h en 0x7f f i s wr i t t e n t o t h e v a g a i n reg i st er , t h e p o w e r o u t p u t is s c al e d u p b y 50 % . 0x7 ff = 204 7d, 2 047 /2 12 = 0. 5. s i m i l a rly , 0x8 00 = C2 047 d (s ig ne d , tw o s c o m p lem e n t ) and p o wer o u t p u t is s c aled b y C50 % . e a c h ls b r e p r es en ts 0.0244% o f the po w e r o u t p u t . t h e a p pa r e n t p o w e r is c a lcu la t e d wi th th e cu rr en t a n d v o l t a g e r m s val u es ob t a i n e d in t h e r m s b l o c ks o f t h e ad e7763. f i gu r e 65 s h o w s t h e m a xim u m co de (h exadec im al) o u t p u t ra n g e o f t h e a p p a r e n t p o w e r sig n al. n o t e t h a t t h e o u t p u t ra n g e c h a n g e s de p e n d i n g o n t h e co n t en t s o f t h e a p p a r e n t p o we r ga in r e g i sters. th e minim u m ou t p u t ra n g e is g i v e n w h e n t h e a p p a r e n t p o w e r ga in r e g i s t er co n t en t is eq ual t o 0x800; th e max i m u m r a nge is g i ven b y wr it ing 0 x 7 f f to t h e a p p a r e n t p o w e r ga in reg i st er . this ca n b e us e d t o cal i b r a t e t h e a p p a r e n t p o w e r (o r en erg y ) calc u l a t ion in th e ad e7763. 0x10 3880 0xa d055 0x5 682b 0x0 0000 0x000 0x7ff 0x800 {v ag a i n[ 11: 0] } a p p are nt p o w e r 100% f s a p p a r e n t p o w e r 150% f s ap p a re nt p o w e r 5 0 % f s apparent power calibration range, voltage and current channel inputs: 0.5v/gain 04481-a - 066 f i gure 65. a p pa r e n t p o w e r ca lc ul ati o n o u tput rang e apparent power o ffset calibration e a ch r m s m e asur em e n t i n cl u d es a n o f fs et co m p en s a t i o n r e g i st er t o cal i b r a t e an d e l imina t e t h e dc com p on e n t i n t h e r m s v a l u e se e t h e ch a n n e l 1 r m s calcula t i o n a n d ch a n n e l 2 rm s calcula t i o n sect i o n s . th e ch a n n e l 1 a n d ch a n n e l 2 rm s v a l u e s a r e t h e n m u lt i p l i e d t o g e t h er i n t h e a p p a r e n t p o w e r sig n al p r o c essin g . b e c a us e n o addi t i onal o f fs ets a r e cr e a t e d in t h e m u l t i p li ca t i o n of t h e r m s val u es , t h er e is n o sp e c if ic o f fs et co m p ens a t i on i n t h e a p p a r e n t p o w e r sig n al p r o c essing. th e o f fs et co m p en s a t i o n o f t h e a p p a r e n t p o wer m e asur em e n t is d o n e b y cali b r a t i n g ea c h in d i v i d u al rm s m e as u r e m en t .
ade7763 rev. a | page 32 of 56 apparent e n ergy cal c ulation the a p p a r e n t e n erg y is g i v e n as t h e in t e g r al o f t h e a p pa r e n t po w e r . = dt t power apparent energy apparent ) ( (26) the ad e7763 ac hiev es t h e in t e g r a t io n o f t h e a p p a r e n t p o wer sig n al b y con t in uo us l y acc u m u l a t i n g t h e a p p a r e n t p o w e r sig n al in an in t e r n al 4 9 -b i t r e gis t er . th e a p p a r e n t en er g y r e gis t er (v aener g y[2 3 :0]) r e p r es en ts t h e u p p e r 24 b i t s o f t h is in t e r n al r e gi s t e r . t h i s d i scr e t e tim e a c cum u la ti o n o r s u m m a ti o n i s e q ui vale n t t o in t e g r a t ion in co n t in uo us t i me . e q ua t i o n 29 exp r ess e s t h is r e la t i on shi p . ? ? ? ? ? ? ? ? ? ? = = 0 0 ) ( n t t nt power apparent lim energy apparent (27) wher e: n is the d i scr e t e n u m b er o f tim e sa m p les. t is t h e tim e sam p le p e r i o d . t h e d i sc r e t e t i m e sa m p l e p e ri od ( t ) f o r th e ac cu m u la ti o n r e g i s t er is 1.1 s (4/clki n ). f i gur e 66 sh o w s t h is dis c r e t e t i m e in t e g r a t io n o r acc u m u l a t i on. t h e a p p a r e n t p o w e r sign al is c o n t in uo us l y add e d t o t h e in t e r n al r e g i st er . this a d di t i on is a s i g n e d addi t i o n , e v en if t h e a p p a r e n t en erg y alwa ys r e ma in s p o si t i v e in t h e o r y . the 49 b i ts o f t h e in t e r n al r e g i st er a r e divi de d b y v a d i v . i f t h e val u e i n t h e v a d i v r e g i st er is 0, t h e n t h e in t e r n al ac t i v e e n erg y r e gis t er is d i vided b y 1. v a d i v is a n 8-b i t, un sign e d r e gis t er . the u p p e r 24 b i ts a r e t h en wr i t ten i n t h e 24- b i t a p p a r e n t e n erg y r e g i s t er (v aener g y[23:0]). r v aener g y r e g i s t er (24 b i ts lo n g ) is p r o v ide d t o r e ad t h e a p p a r e n t e n erg y . this r e g i st er is re s e t to 0 af te r a re ad op e r a t i o n. f i gur e 67 sh o w s this a p p a r e n t en er g y acc u m u la tio n f o r f u l l - s c ale sig n als (sin us o i dal) o n t h e a n alog in pu ts. the t h r e e c u r v es i l l u st ra t e t h e mi nim u m t i m e fo r t h e e n erg y r e g i st er t o r o l l o v er when t h e v a gain r e g i st ers c o n t en t is eq ual to 0x7ff , 0x000, a n d 0x800. th e v a gain r e g i ster is us ed t o ca r r y o u t a n a p pa r e n t po w e r c a li b r a t i o n . a s s h o w n in th e f i gu r e , th e fa s t es t in teg r a t ion t i me o c c u rs w h en t h e v a gain r e g i st er is s e t t o max i m u m f u l l s c a l e, i. e. , 0 x 7 f f . vadiv apparent power + + vaenergy[23:0] ap p a re nt p o w e r i s ac cum u l at e d ( i n t e g rat e d ) i n t h e a pp a r en t e n e r g y r eg i s t e r 23 0 48 0 48 0 04481-a - 067 % time (nt) t a c t i ve po w e r si g n a l = p f i gure 6 6 . a p par e nt ener gy c a l c u l a t ion 0 xff ffff 0x80 0000 0x40 0000 0x20 0000 0x00 0000 vaenergy[23:0] 6.26 12.52 18.78 25.04 time (minutes) vagain = 0x7ff vagain = 0x000 vagain = 0x800 04481-a - 068 f i gure 6 7 . ener gy r e gi st er rol l o v er t i m e f o r f u ll -s c a l e p o w e r (m ax i m u m and m i ni m u m p o we r g a in ) n o t e t h a t t h e a p p a r e n t e n erg y r e g i st er is un sig n e d s e e f i gur e 67. b y usin g th e in t e r r u p t ena b l e r e g i s t er , t h e ad e7763 ca n be co nf igure d t o i ssue a n in ter r u p t ( ir q ) wh en t h e a p p a r e n t en e r g y r e gis t er is m o r e tha n half f u l l o r when an o v er f l o w o c c u r s . t h e half f u l l in t e r r u p t fo r t h e un sig n e d a p p a r e n t e n erg y r e g i st er is bas e d on 24 b i ts , as o p p o s e d t o 23 b i ts fo r the sig n e d ac ti v e en erg y r e g i st er .
ade7763 rev. a | page 33 of 56 integr ation ti mes un der ste a d y loa d a s m e n t i o n e d in t h e l a s t secti o n , t h e d i sc r e t e tim e sa m p l e pe ri od ( t ) f o r th e accum u la t i o n r e gis t er is 1.1 s (4/clk in ). w i t h f u l l -s cale sin u s o idal sig n a l s o n t h e analog in p u ts an d t h e v a gain r e g i ster s e t t o 0x000, th e a v er a g e w o r d val u e f r o m t h e a p p a r e n t p o w e r st a g e is 0xa d0 55. the maxi m u m val u e t h a t ca n be st o r ed in th e a p p a r e n t en er g y r e gis t er bef o r e i t o v er f l o w s is 2 24 o r 0xff ffff . th e a v er a g e w o r d val u e is adde d t o t h e in t e r n a l r e g i st er , which can st o r e 2 48 o r 0xfff f ffff f fff b e fo r e i t o v er f l o w s. th er efo r e , t h e in t e g r a t ion t i m e u n der t h es e co ndi t io n s wi t h v a d i v = 0 is calc u l a t ed as f o l l o w s: min 52 . 12 888 2 . 1 0xad055 ffff ffff 0xffff = = = s s time (28) whe n va d i v is set t o a val u e o t h e r than 0, t h e in tegra t io n tim e va r i es, as sh o w n in e q ua tio n 29. ti m e = ti m e wd i v = 0 va d i v ( 2 9 ) line ap par e nt energ y accumul a tio n the ad e7763 is desig n ed wi th a s p ec ial a p p a r e n t en erg y acc u m u la tio n m o de , which sim p lif i es t h e cal i b r a t io n p r o c es s. b y usin g th e o n -c hi p zer o -cr o s s in g det e c t ion, t h e ad e7763 a c cu m u l a t e s th e a p pa r e n t po w e r s i gn al i n th e l v a e n e r g y r e g i st er fo r a n in t e g r al n u m b er o f half c y cles, as sho w n i n f i gur e 68. th e l i n e a p p a r e n t en er g y acc u m u la tio n m o d e is al w a ys a c t i v e . the n u m b er o f half li n e c y cles is sp e c if ie d i n t h e linec y c r e g i s t er , whic h is a n un sig n e d , 1 6 -b i t r e g i s t er . th e ad e7763 can acc u m u la te a p p a r e n t p o wer fo r u p t o 65,535 co m b in e d half c y cles. b e ca us e t h e a p p a r e n t p o w e r is in teg r a t e d o n t h e s a me in teg r al n u m b e r o f lin e c y cles as t h e l i n e ac t i v e en erg y r e g i st er , t h ese t w o val u e s ca n be e a si l y co m p a r e d . th e act i v e a n d a p p a r e n t en erg i es a r e c a lc u l a t e d m o r e ac c u ra t e ly b e c a us e o f t h is p r e c is e t i mi n g co n t r o l. a t t h e e n d o f a n en erg y cal i b r a t i o n c y cle , t h e cy ce n d f l ag in t h e in t e r r u p t s t a t us r e gis t er is set. i f the cy ce nd mask b i t in t h e i n t e r r u p t mask r e g i ster is ena b le d , t h e ir q o u t p u t also wil l g o ac ti v e lo w . th us, the ir q lin e can als o be use d t o sign a l th e en d o f a ca li b r a t io n. t h e lin e a p pa r e n t en e r g y a ccum u la ti o n uses th e sa m e si g n al p a th as t h e a p p a r e n t en erg y acc u m u l a t i o n . th e ls b size o f t h es e t w o re g i ste r s i s e q u i v a l e n t . vadiv[7:0] lpf1 + + lvaenergy[23:0] lvaenergy register is updated every linecyc zero crossings with the total apparent energy during that duration apparent power from channel 2 adc 23 0 linecyc[15:0] 48 0 04481-a - 069 % zero-crossing detection calibration control f i gure 6 8 . a p par e n t ener gy c a l i b r a tion
ade7763 rev. a | page 34 of 56 energies scaling the ad e7763 p r o v ides m e as urem en ts o f ac t i v e a n d a p p a r e n t en erg i es. th e s e m e asur e m en ts do n o t ha v e t h e s a m e s c alin g and t h er efo r e ca nn ot b e com p a r e d dir e c t ly t o e a ch ot h e r . ta bl e 7. e n ergi es s c ali n g pf = 1 pf = 0. 707 pf = 0 integrator on at 50 hz active wh wh 0.707 0 apparent wh 0.848 wh 0.848 wh 0.848 integrator off at 50 hz active wh wh 0.707 0 apparent wh 0.848 wh 0.848 wh 0.848 integrator on at 60 hz active wh wh 0.707 0 apparent wh 0.827 wh 0.827 wh 0.827 integrator off at 60 hz active wh wh 0.707 0 apparent wh 0.827 wh 0.827 wh 0.827 calibrating an energy meter the ad e7763 p r o v ides gain and o f fs et co m p ens a tio n fo r ac ti v e and a p p a r e n t energ y ca l i b r a t io n. i t s p h as e co m p en s a t i o n co r r e c ts phas e er r o r in ac t i v e an d a p p a ren t e n erg y . i f a sh un t is us e d , o f fs et a n d pha s e ca l i b r a t io n ma y n o t b e r e q u ir e d . a r e fer e n c e me te r or an ac c u r a te s o u r c e c a n b e u s e d to c a l i b r a t e th e ad e7763. w h en usin g a refer e n c e m e ter , th e ad e7763 c a lib r a t ion o u t p u t f r eq uen c y , cf , is ad j u s t e d t o m a t c h t h e f r eq uen c y o u t p u t o f the r e fer e n c e m e t e r . a p u ls e o u t p u t is o n ly p r o v ide d fo r t h e ac t i v e en erg y m e as ur em en t in t h e ade7763. i f a r e fer e n c e m e t e r is us e d t o cal i b r a t e t h e v a , t h e n addi t i o n al co de m u st b e wr i t t e n in a m i cr o p r o ces s o r t o p r o d uce a p u ls ed o u t p u t f o r this q u an t i ty . o t h e r w is e , v a c a lib r a t io n r e q u ir es an acc u ra t e s o ur ce. the ad e 7 7 6 3 p r o v id es a l i n e c y c l e a ccum u la ti o n m o d e f o r c a l i b r a t i o n u s i n g a n acc u r a t e s o ur ce . i n t h is m e th o d , t h e ac ti v e en er g y acc u m u l a tio n ra t e is ad j u s t ed t o p r o d uc e a d e sir e d cf f r e q u e n c y . the b e n e f i t o f usi n g t h i s mo de is t h a t t h e ef fe c t o f t h e ri p p l e n o is e on t h e ac t i v e en erg y is e l imina t e d . u p t o 65,535 ha lf line c y cles ca n b e acc u m u la t e d , t h er efo r e p r o v i d in g a st a b le en erg y val u e t o a v era g e. th e ac c u m u l a t i o n t i me is calc u l a t e d f r o m t h e li ne c y cle p e r i o d , me asur e d b y t h e p e r i o d r e g i st er , and t h e n u m b er o f half li n e c y cles in t h e acc u m u la t i o n , f i xe d b y t h e linecy c r e g i st er . c u r r en t a n d v o lt a g e r m s o f fs et cal i b r a t io n r e mo v e s a p p a r e n t en erg y o f fs et. a ga in c a lib r a t ion is a l s o p r o v ide d fo r a p p a r e n t en erg y . f i gur e 7 0 sho w s an o p t i mi ze d cal i b r a t ion f l o w fo r ac t i v e en erg y , r m s, and a p p a r e n t e n erg y . a c ti v e an d a p p a r e n t en er g y ga in cal i b r a t io n s c a n take p l ace c o nc u r re n t ly , w i t h a re a d of t h e a c c u m u l a te d a p p a re n t e n e r g y r e g i st er fol l o w i n g t h a t o f t h e ac c u m u l a t e d ac t i ve en erg y r e g i st e r . f i gur e 69 sh o w s t h e cal i b r a t io n f l o w fo r t h e ac t i v e en erg y p o r t io n o f th e ad e7763. watt gain calibration watt offset calibration phase calibration 04481- a - 083 f i gure 6 9 . a c ti v e en er gy c a l i b r a tio n watt/va gain calibration watt offset calibration rms calibration phase calibration 04481-a-084 f i gure 70. a p par e n t and a c tiv e ener gy c a libr ation
ade7763 rev. a | page 35 of 56 watt g a in the f i rst st ep o f cal i b r a t in g t h e ga in is t o def i ne t h e l i n e v o l t a g e, t h e b a s e c u r r en t , a n d t h e maxi m u m c u r r e n t fo r t h e m e t e r . a m e t e r co n s tan t , s u c h as 3200 im p/kw h o r 3.2 im p/w h , n e eds to b e de te r m i n e d f o r c f . n o te t h a t t h e l i ne volt age and t h e maxim u m c u r r en t s c ale t o half o f t h eir r e sp e c t i v e a n alog in p u t ra n g es in t h is exa m ple . the exp e c t e d c f in h z is cf expe ct e d (h z) = ) cos( s/h 3600 ) w ( ) imp/wh ( ? load ant meterconst (30) wher e: ? is t h e an g l e b e t w e e n i and v . cos is t h e p o w e r fac t o r . ) ( ? the ra t i o o f ac t i v e en erg y ls bs p e r cf p u ls e is ad j u st e d usin g t h e cf nu m, c f den, and wdi v r e g i sters. cf expe ct e d = ) 1 ( ) 1 ( (s) + + cfden cfnum wdiv ontime accumulati laenergy (31) the r e l a t i on sh ip b e tw e e n w a tt- h o u rs ac c u m u l a te d and t h e q u an ti ty r e ad f r o m aen e rgy ca n be d e t e r m in e d f r o m the a m o u n t o f ac t i ve en erg y acc u m u la t e d o v er t i me wi t h a gi v e n l o a d : s/h 3600 ) ( (w) lsb wh = laenergy s time on accumulati load (32) wher e a ccu m u la tio n t i m e ca n b e det e r m i n e d f r o m t h e val u e i n t h e l i n e p e r i o d a n d t h e n u m b er o f half line c y cles f i xe d in t h e linecy c r e g i st er . a c c u m u la tio n ti m e (s) = 2 ) ( s period line linecyc ib (33) t h e l i n e pe ri o d c a n be d e t e rm in ed f r o m th e peri od r e gi s t e r : li n e pe r i o d (s) = pe r i od clkin 8 ( 3 4 ) the ae ner g y w h /ls b ra t i o c a n als o b e exp r ess e d in t e r m s o f th e m e t e r co n s t a n t : (imp/wh) ) 1 ( ) 1 ( lsb wh ant meterconst wdiv cfden cfnum + + = ( 3 5 ) i n a m e t e r des i g n , w d i v , cf nu m, a n d cfd e n sh o u ld be kep t co n s ta n t a c r o s s all m e t e r s t o e n s u r e th a t th e w h / l s b co n s ta n t i s m a i n ta in e d . l e a v in g w d iv a t i t s d e fa ul t v a l u e o f 0 e n s u r e s max i m u m r e s o lu t i o n . the wdi v r e g i ster is no t inc l ude d i n t h e cf sign al c h a i n , so i t d o es n o t af f e c t th e f r eq uen c y p u lse o u t p u t . the w g ai n r e g i st er is us e d t o f i n e ly c a l i b r a t e e a ch m e t e r . c a li - b r a t i n g t h e w g ai n reg i st er chan g e s b o t h cf and ae ne r g y f o r a g i ven lo a d co ndi t ion. aenergy expe c t e d = aenergy no m i nal ? ? ? ? ? ? + 12 2 1 wgain (36) cf expe ct e d (h z) = cf no m i nal ? ? ? ? ? ? + + + 12 2 1 ) 1 ( ) 1 ( wgain cfden cfnum ( 3 7 ) whe n c a l i br a t i n g w i t h a re f e re nc e m e te r , w g a i n i s a d ju ste d un t i l cf ma t c h e s t h e r e fer e n c e m e t e r p u ls e o u t p u t . i f an acc u ra t e s o ur ce is us e d t o cal i b r a t e , w g ain wil l be m o dif i e d un t i l t h e ac t i v e en erg y acc u m u l a t i o n ra t e yi e l ds t h e ex p e c t e d c f pu l s e r a te. the steps o f desig n in g and c a l i b r a t in g t h e ac t i v e en erg y p o r t io n o f a m e t e r wi t h ei t h er a r e fer e n c e met e r o r a n ac c u ra t e s o ur ce a r e o u t l i n e d in t h e fol l o w in g ex a m ples. th e sp e c if ica t ion s fo r t h is exa m ple a r e me t e r c o n s t a n t : me t e r c o n s t a n t (im p /w h ) = 3.2 ba se c u rr e n t: i b = 10 a ma x i mu m c u r r e n t : i ma x = 60 a lin e v o l t a g e : v nom i nal = 220 v l i ne f r e q u e nc y : f l = 50 h z the f i rst st ep i n cal i b r a t io n wi t h ei t h er a r e fer e n c e met e r o r a n acc u ra t e s o ur ce is t o calc u l a t e t h e cf den o m i na to r , cfd e n . this is don e b y co m p a r in g t h e exp e c t e d cf p u ls e o u t p ut t o t h e n o m i n a l c f o u t p u t w i th th e d e fa u l t c f d e n = 0 x 3 f a n d cfn u m = 0x3f wh en t h e base c u r r en t is a p p l ied . t h e exp e c t e d cf o u t p u t f o r this m e t e r wi t h t h e base c u r r en t a p p l ie d is 1.955 6 h z usin g e q u a tio n 30. cf ib ( expe ct e d ) (h z) = hz 9556 . 1 ) cos( s/h 3600 v 220 a 10 imp/wh 200 . 3 = ? al ter n a t i v ely , cf expe ct e d ca n b e me asur e d f r o m a r e fer e n c e m e ter pu l s e outp ut . cf expe ct e d (h z) = cf re f (38) the max i m u m cf f r e q uenc y me asur e d wit h o u t an y f r e q uenc y d i visio n an d wi t h ac in p u ts a t f u l l scale is 23 kh z. f o r this exa m ple , t h e n o minal cf wi t h t h e t e st c u r r en t, i b , a p plie d is 958 h z . i n t h is exa m p l e t h e line v o l t a g e and maxim u m c u r r en t s c ale half o f t h e i r r e sp e c t i v e a n a l og in p u t ra n g es . the li n e v o l t a g e an d maxim u m c u r r en t sh o u l d n o t b e f i xe d a t t h e max i m u m an a l o g in p u ts to ac c o un t fo r o c c u r r enc e s such as sp i k es o n t h e li n e .
ade7763 rev. a | page 36 of 56 cf no m i nal (h z) = max i i 2 1 2 1 khz 23 ( 3 9 ) cf ib ( no m i nal ) (h z ) = hz 958 60 10 2 1 2 1 khz 23 = t h e n o m i nal cf o n a s a m p le s e t o f m e t e rs sh o u ld be m e as ur e d usin g the d e f a ul t cfd e n , cfnu m, a n d w d iv t o en s u r e tha t t h e b e st cfd e n is ch os en fo r t h e desig n . w i t h t h e cfn u m r e gis t er set t o 0, cfd e n is ca lc ula t e d t o be 489 fo r th e exa m p l e m e t e r : cfd e n = 1 ) ( ) ( ? ? ? ? ? ? ? ? ? expected ib nominal ib cf cf int (40) cfd e n = 489 ) 1 490 ( 1 9556 . 1 958 = ? = ? ? ? ? ? ? ? int t h i s v a lu e f o r c f de n s h ou l d b e l o a d e d i n to e a ch me te r b e f ore cali b r a t i o n . th e w g a i n r e gi s t e r ca n t h en be used t o f i n e l y cal i b r a t e t h e cf o u t p ut. th e fol l o w in g s e c t io n s expla i n h o w t o cal i b r a t e a met e r bas e d o n ad e 7763 when using a r e f e r e n c e m e t e r o r a n acc u ra t e so ur ce. calibrating w a tt g a in using a r e ference meter exampl e the cfd e n and cfnu m val u es fo r t h e desig n sh o u ld b e w r itte n to t h e i r re sp e c t i ve re g i s t e r s b e f ore b e g i n n i n g t h e c a l i br a t i o n s t e p s sh ow n i n fi g u re 7 1 . whe n u s i n g a re f e re nc e m e t e r , t h e p e r c en t er r o r in cf is m e as ur ed b y co m p a r in g t h e cf o u t p u t o f the ad e7763 m e ter wi th t h e p u ls e ou t p u t o f the re fe re nc e me te r , u s i n g t h e s a me te st c o nd i t i o n s for b o t h me te r s . eq ua ti o n 41 d e f i n e s t h e pe r c en t e r r o r w i th r e s p ect t o t h e p u lse o u t p u t s o f bo t h m e t e rs (usin g t h e bas e c u r r en t, i b ): % erro r cf ( ib ) = 100 ) ( ) ( ? ib ref ib ref ib cf cf cf (41) calculate cfden value for design write cfden value to cfden register addr. 0x15 = cfden write wgain value to the wgain register: addr. 0x12 measure the % error between the cf output and the reference meter output set i test = i b , v test = v nom , pf = 1 04481-a - 085 calculate wgain. see equation 42. f i gure 7 1 . c a l i b r a ting w a tt g a in usi n g a refer e nc e m e t e r f o r t h is exa m ple: me t e r c o n s t a n t : me t e r c o n s t a n t (im p /w h) = 3.2 cf n u m e r a t o r : cf nu m = 0 cf d e n o mina to r : cfden = 489 % e r r o r m e a s u r e d a t b a s e c u r r e n t : % erro r cf ( ib ) = ?3.07% on e l s b cha n ge in wg a i n cha n g e s t h e ac t i ve en erg y r e g i st ers a n d cf b y 0.02 44% . wg a i n is a signed , tw os c o m p lem e n t r e g i s t er a n d c a n co r r ec t u p t o a 50% er r o r . a s s u m i n g a ?3.07% er r o r , wg a i n is 126: wg a i n = in t ? ? ? ? ? ? ? ? ? % 0244 . 0 % ) ( ib cf error (42) wg a i n = in t 126 % 0244 . 0 % 07 . 3 = ? ? ? ? ? ? ? ? w h en cf is cal i b r a t e d , t h e ae ner g y r e g i st e r has t h e s a me w h / l s b c o nst a n t f r om me te r t o me te r i f t h e me te r c o nst a n t , wd iv , and t h e cfnu m/ cfd e n ra t i o r e ma i n t h e s a me . th e w h /ls b ra t i o fo r this m e t e r is 6.378 10 ?4 usin g e q ua t i o n 35 wi t h wd iv a t t h e defa u l t val u e. (imp/wh) ) 1 ( ) 1 ( lsb wh ant meterconst wdiv cfden cfnum + + = 4 10 378 . 6 2 . 3 490 1 imp/wh 200 . 3 ) 1 490 ( 1 lsb wh ? = = + = calibratin g w a tt gain using an accurate source example the cf den v a lue ca lc u l a t e d usin g e q u a t i on 40 sh o u l d b e wr it te n to t h e c f d e n r e g i ster b e fo r e b e g i nn ing ca l i b r a t io n and zer o sh o u ld be wr i t t e n t o t h e cfnu m r e g i s t er . ena b le t h e l i n e acc u m u la tion m o de and t h e lin e acc u m u la t i o n in t e r r u p t. th en, wr i t e t h e n u m b er o f half lin e c y cles fo r t h e en erg y acc u m u l a t i on to t h e l i ne c y c re g i ste r to set t h e accum u la tio n tim e . re s e t t h e i n ter r u p t st a t u s r e g i st er a n d w a i t f o r t h e l i ne c y c l e a c c u m u l a t i o n in t e r r u p t. th e f i rs t li n e c y cle acc u m u l a t i o n r e su l t s mig h t n o t us e t h e acc u m u l a t i o n t i m e se t b y th e l i n e c y c r e g i s t e r a n d , t h erefo r e, sh ou l d b e di s c a r de d . af ter re s e tt i n g t h e i n t e r r upt st a t us r e g i st er , t h e fol l o w in g li ne c y cle r e adin gs wi l l b e v a li d . w h en linecy c half lin e c y c l es ha v e e l a p s e d , t h e ir q pi n g o es a c ti v e lo w a n d th e n o m i nal la ene r gy w i t h t h e te s t c u r r e n t a p plie d can b e r e ad . this l a ener gy va l u e is c o m p a r e d t o t h e exp e c t e d l a e n er gy val u e t o det e r m i n e t h e w g ai n v a l u e . i f a p p a r e n t e n erg y ga in c a lib r a t ion is p e r f o r m e d a t t h e s a me t i me , l v aener g y c a n b e r e ad dir e c t ly a f ter l a ene r gy . b o t h re g i ste r s s h ou l d b e re a d b e f o re t h e ne x t i n te r r upt i s i ssu e d o n th e ir q p i n. f i gur e 72 det a i l s steps t o cal i b r a t e t h e wa t t ga i n usin g a n acc u ra t e s o ur ce .
ade7763 rev. a | page 37 of 56 write wgain value to the wgain register: addr. 0x12 calculate cfden value for design write cfden value to cfden register addr. 0x15 = cfden set half line cycles for accumulation in linecyc register addr. 0x1c set i test = i b , v test = v nom , pf = 1 calculate wgain. see equation 43. set mode for line cycle accumulation addr. 0x09 = 0x0080 enable line cycle accumulation interrupt addr. 0x0a = 0x04 read line accumulation energy addr. 0x04 reset the interrupt status read register addr. 0x0c interrupt? no no yes yes 04481-a - 086 reset the interrupt status read register addr. 0x0c interrupt? f i gure 7 2 . c a l i b r a ting w a tt g a in usi n g a n a c cur a te so urc e eq u a ti o n 43 d e s c ri be s th e r e la tio n s h i p bet w e e n th e e x pect e d l a e n er gy v a lue a n d t h e l a e n er gy m e asur e d i n t h e t e st co ndi t ion: wg a i n = in t ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? nominal ib expected ib laenergy laenergy (43) the n o m i nal l a ener gy r e ading, lae n ergy ib ( nom i nal ) , is the l a en er gy r e adi n g wi t h t h e t e st c u rr en t a p p l i e d . th e e x pe ct e d l a e n er gy r e adin g is calc u l a t e d f r o m t h e fol l o w in g e q ua t i o n : la e n e r g y ib ( ex p e ct e d ) = int ? ? ? ? ? ? ? ? ? ? ? ? ? ? + + wdiv cfden cfnum time on accumulati cf expected ib 1 1 (s) ) ( (44) wh er e cf ib ( ex pe ct e d ) (h z) is c a lc ul a t ed f r o m e q ua tio n 30, acc u m u la tion tim e is calc u l a t e d f r o m e q ua tio n 33, a n d t h e line per i o d is d e t e rm i n ed fr o m th e p e ri od r e g i s t e r a c c o r d i n g t o eq u a tio n 3 4 . f o r t h is exa m ple: me t e r c o n s t a n t : me t e r c o n s t a n t (im p /w h) = 3.2 te s t c u r r e n t : i b = 10 a lin e v o l t a g e : v nom i nal = 220 v l i ne f r e q u e nc y : f l = 50 h z ha l f l i n e c y c l e s : linecy c ib = 2 0 00 cf n u m e r a t o r : cf nu m = 0 cf d e n o mina to r : cfden = 489 en erg y re adi n g a t b a s e c u r r en t : l a en ergy ib ( nom i nal ) = 17174 p e r i o d reg i st er re a d i n g: pe r i od = 8959 cloc k f r eq uen c y : clki n = 3.579 5 45 mh z cf ex pe ct e d is calc ula t e d t o be 1.95 56 h z ac co r d ing t o e q ua t i o n 3 0 . la en er g y expe ct e d is calc u l a t ed to be 19186 using e q ua tion 44. cf ib ( expe ct e d ) (h z) = ) cos( s/h 3600 a 10 v 220 imp/wh 200 . 3 ? = 1.9556 h z la e n e r g y ib ( ex p e ct e d ) = int ? ? ? ? ? ? ? ? ? ? ? ? ? ? + + wdiv cfden cfnum clkin period linecyc cf ib expected ib 1 1 / 8 2 / ) ( la e n e r g y ib ( ex p e ct e d ) = int 1 1 489 1 ) 10 579545 . 3 /( 8 8959 2 / 2000 9556 . 1 6 ? ? ? ? ? ? ? ? ? ? ? ? + = 19186 ) 4 . 19186 ( = int
ade7763 rev. a | page 38 of 56 w g ai n is c a lc u l a t e d t o be 480 usin g e q ua t i o n 43. wg a i n = in t 480 2 1 17174 19186 12 = ? ? ? ? ? ? ? ? ? ? ? ? ? n o t e t h a t w g ain is a sig n e d , tw os co m p lem e n t r e gis t er . wi t h wd iv and cf n u m s e t to 0, l a en ergy ca n be exp r es s e d as la e n e r g y ib ( ex p e ct e d ) = )) 1 ( / 8 2 / ( ) ( + cfden clkin period linecyc cf int ib expected ib the calc u l a t e d w h /ls b ra t i o fo r t h e ac t i v e e n erg y r e g i s t er , usin g e q ua t i o n 35 is 6.378 10 ?4 is 4 10 378 . 6 imp/wh 200 . 3 ) 1 489 ( 1 lsb wh ? = + = watt offset of fs et cal i b r a t ion al lo ws o u ts t a ndin g p e r f o r ma n c e o v er a wide d y na mic ran g e , f o r exa m p l e , 1000:1. t o do this cal i b r a t io n tw o m e as u r em e n t s a r e n eeded a t u n i t y po w e r fa c t o r , o n e a t i b an d t h e ot h e r a t t h e lo w e s t c u r r en t to b e co r r e c t e d . ei t h er cal i b r a- t i on f r e q u e nc y or l i ne c y cl e a c c u m u l a t i on m e a s u r e m e n t s c a n b e us e d t o de t e r m i n e t h e e n erg y o f fs et. gain cal i b r a t io n sh o u ld b e p e r f or me d pr i o r to of f s e t c a l i br a t i o n . o f f s et cali b r a t i o n is pe rf o r m e d b y d e t e rm in i n g th e a c ti v e en e r g y er r o r ra t e . af t e r d e t e r m in in g t h e acti v e en er g y er r o r ra t e , calcu- la te t h e v a l u e t o wr i t e t o t h e a p os r e g i s t er t o c o r r e c t t h e o f fs et . apos = ? clkin rate error aenergy 35 2 ( 4 5 ) the ae ner g y r e g i s t ers u p da te a t a r a t e o f cl kin/4. th e tw o s co m p lem e n t apos r e gis t er p r o v ides a f i n e ad j u s t m e n t t o t h e ac t i v e p o w e r ca l c u l a t ion. i t r e p r es en ts a f i xe d am o u n t o f p o w e r o f fs et t o b e ad j u s t e d e v er y clki n/4. th e 8 ls b s o f t h e a p os r e g i s t er a r e f r ac t i o n al s u ch t h a t o n e ls b o f a p os r e p r es en ts 1/256 o f th e leas t sig n if ica n t b i t o f th e in t e r n al ac ti v e en erg y r e g i s t er . th er efo r e , o n e ls b o f t h e apos r e g i ster r e p r es en ts 2 ?3 3 o f t h e ae ner g y[23:0] ac t i v e e n erg y r e g i s t er . s e e t h e fol l o w i n g s e c t io n s fo r s t eps t o det e r m i n e t h e ac t i ve en erg y er r o r ra t e fo r b o t h li ne acc u m u l a t i on and r e fer e n c e me te r c a l i br a t i o n opt i ons . calibratin g watt offset usin g a reference meter example f i gur e 73 sh o w s t h e s t eps in v o lv e d i n cal i b r a t i n g wa t t o f fs et wi t h a r e fer e n c e m e ter . write apos value to the apos register: addr. 0x11 measure the % error between the cf output and the reference meter output, and the load in watts set i test = i min , v test = v nom , pf = 1 04481-a - 087 calculate apos. see equation 45. f i gure 7 3 . c a l i b r a ting w a tt o ffset usi n g a refer e nc e m e ter f o r t h is exa m ple: me t e r c o n s t a n t : me t e r c o n s t a n t ( i m p /w h) = 3. 2 mini m u m c u r r e n t : i min = 40 ma loa d a t m i ni m u m c u rr e n t : w imin = 9.6 w cf er r o r a t m i nim u m c u r r en t : % erro r cf ( imin ) = 1.3% cf n u m e r a t o r : cf nu m = 0 cf d e n omin a to r : c de n = 489 c l o c k f r e q u e n c y : c kin = 3.579545 mh z us i n g e q u a t i o n 4 5 , apo s is ? 5 2 2 f o r this exam p l e . cf a b s o l u te e r r o r = c f imin ( nom i nal ) ? c f imin ( ex pe ct e d ) (46) cf a b s o l u te e r r o r = (% erro r cf ( imin ) ) w imin 3600 (imp/wh) ant meterconst (47) cf a b s o l u te e r r o r = hz 000110933 . 0 3600 200 . 3 6 . 9 100 % 3 . 1 = ? ? ? ? ? ? then, aenergy e r r o r ra t e (ls b /s) = cf a b s o l u te e r r o r 1 1 + + cfnum cfden (48) aenergy e r r o r ra t e (ls b /s) = 0.000110933 05436 . 0 1 490 = u s in g e q u a tion 45, apos is ?5 22. apos = ? 522 10 579545 . 3 2 05436 . 0 6 35 ? = apos ca n b e r e p r es en ted as f o llo ws wi th c f nu m a n d w d iv set a t 0: apos = ? clki n cfden ant meterconst w error imin imin cf 35 ) ( 2 ) 1 ( 3600 (imp/wh) ) (% +
ade7763 rev. a | page 39 of 56 calibratin g watt offset wi th an accurate source exampl e f i gur e 74 is t h e f l o w cha r t fo r wa t t o f fs et ca l i b r a t io n wi t h an acc u ra te s o ur ce. set half line cycles for accumulation in linecyc register addr. 0x1c set i test = i min , v test = v nom , pf = 1 calculate apos. see equation 45. set mode for line cycle accumulation addr. 0x09 = 0x0080 enable line cycle accumulation interrupt addr. 0x0a = 0x04 read line accumulation energy addr. 0x04 reset the interrupt status read register addr. 0x0c interrupt? no no yes yes reset the interrupt status read register addr. 0x0c interrupt? write apos value to the apos register: addr. 0x11 04481-a - 088 f i gure 7 4 . c a l i b r a ting w a tt o ffset wi th a n a c cur a t e s o urc e f o r t h is exa m ple: me t e r c o n s t a n t : me t e r c o n s t a n t (im p /w h) = 3.2 lin e v o l t a g e : v nom i nal = 220 v l i ne f r e q u e nc y : f l = 50 h z cf n u m e r a t o r : cf nu m = 0 cf d e n omin a to r : cfden = 489 ba se c u rr e n t: i b = 10 a h a l f l i ne cy c l e s u s e d a t b a s e cu r r e n t : linecy c ( ib ) = 2000 p e r i o d reg i st er re a d i n g: pe r i od = 8959 cloc k f r eq uen c y : clki n = 3.579 545 mh z expect ed la en e r g y r e gis t er v a l u e a t base c u rr e n t ( f r o m t h e w a t t g a i n s e c t i o n ) : la e n e r g y ib ( ex p e ct e d ) = 19186 mini m u m c u r r e n t : i min = 40 ma n u m b er o f h a lf line c y c l es use d a t minim u m c u r r en t: linecy c ( imin ) = 35700 a c t i v e e n erg y re adi n g a t mini m u m c u r r en t: la e n e r g y imin ( no m i n a l ) = 13 95 the l a ener gy exp e c t ed at i min is 1255 usin g e q u a tio n 49. la e n e r g y imi n ( ex pe ct e d ) = int ? ? ? ? ? ? ? ? ) ( (49) la e n e r g y imi n ( ex pe ct e d ) = int 1370 ) 80 . 1369 ( 2000 35700 19186 10 04 . 0 = = ? ? ? ? ? ? wher e: la e n e r g y ib ( expe c t e d ) is t h e exp e c t e d l a e n ergy r e ading a t i b f r o m t h e w a t t g a in c a l i b r a t io n. linecy c imin is t h e n u m b er o f half li n e c y cles t h a t e n erg y is a c cum u la t e d o v er wh en m e as uri n g a t i min . m o r e lin e c y cles co u l d b e r e q u ire d a t t h e mi ni m u m c u r r en t t o mi ni mi ze t h e ef fe c t o f quan t i za t i o n er r o r on t h e o f fs e t ca l i b r a t ion. f o r ex am p l e , if a t e st c u r r en t o f 4 0 m a r e s u l t s in a n ac t i ve ener g y acc u m u l a t i on o f 113 a f t e r 20 00 half l i ne c y c l es, one ls b va r i a t ion in t h is r e adin g rep r es en ts a 0.8 % er r o r . this me as ur emen t do e s n o t p r o v i d e e n oug h r e s o l u t i on to calib r a t e a <1 % o f fs et er r o r . h o w e v e r , if t h e ac ti v e en erg y is acc u m u la t e d o v er 37,500 h a l f line c y c l es , one ls b va r i a t ion res u l t s in 0. 05 % er r o r , r e d u c i ng t h e q u a n tiz a ti o n e r r o r . apos is ?672 u s in g e q u a tio n s 55 a n d 49. la e n e r g y a b s o l u t e e r r o r = la e n e r g y imi n ( nom i nal ) ? l a en er gy imi n ( exp e c t ed ) la e n e r g y a b s o l u t e e r r o r = 1 395 ? 1370 = 25 (50) aenergy e r r o r ra t e (ls b /s) = period clkin linecyc error absolute laenergy 8 2 / (51) aenergy e r r o r ra t e (ls b /s) = 069948771 . 0 8959 8 10 579545 . 3 2 / 35700 25 6 = clkin rate error aenergy 35 2 = ? 672 10 579545 . 3 2 069948771 . 0 6 35 ? = apos = ?
ade7763 rev. a | page 40 of 56 m p en s a t e s f o r p h as e er r o r b y in s e r t in g a smal l t i m e de l a y o r adva n c e o n t h e v o l t a g e chann e l in p u t. p h as e le ads u p t o 1.84 a n d p h as e l a gs u p t o 0.72 a t 50 h z c a n b e co r r ec t e d . the er ro r i s de te r m i n e d b y me asur i n g t h e ac t i v e e n erg y a t i b and tw o p o wer fac t ors, p f = 1 a n d pf = 0.5 ind u c t i v e . s o m e ct s ma y i n t r o d uc e la rg e phas e er r o rs t h a t a r e b e yo n d t h e ra n g e o f t h e phas e cal i b r a t ion r e g i s t er . i n t h is cas e , co a r s e phas e co m p ensa tio n has t o be do ne ex t e r n al l y wi th an a n alog f i l t er . the phas e er r o r ca n b e ob t a i n e d f r o m ei t h er c f o r l a ener g y me a s u r e m e n t s : er r o r = phase c a libration the p h cal r e g i s t er is p r o v i d e d t o r e mo v e smal l phas e er r o rs. the ad e7763 c o 2 2 ) ( ) ( 5 . 0 , expected ib expected ib pf ib laenergy laenergy laenergy ? = (52) i f wa t t ga i n and o f fs et calib r a t ion ha ve b e en p e r f o r m e d , t h er e s h o u l d be 0% er r o r in cf a t uni t y p o w e r fac t o r , a n d t h en er r o r = % error cf ( ib ,p f = 0.5) /100 (53) the phas e er r o r is phase e r r o r () = ?ar c sin ? ? ? ? ? ? ? ? 3 error ( 5 4 ) the r e la t i on s h i p b e tw e e n phas e er r o r a n d t h e p h ca l phas e co r r ec tio n r e gist er is phc a l = in t () + ? ? ? ? ? ? 360 period error phase 0x0d (55) the exp r es sio n fo r p h cal can b e si m p lif i e d usin g t h e a s s u m p ti o n th a t a t s m all x ar csin( x ) x d in t h e v o lt a g e cha n ne l b y p h ca l is a l ? 0x0d) 8/ s a t i m e del a y if si t e , b ts a t i me ad van c e if th i s v e h e i s f phca l = 0 x 0d . c t ion o f t h e ) the de l a y i n t r o d uce de l a y = ( phc clki n (56) the de l a y as s o c i a t e d wi t h t h e ph cal r e g i st er i phc a l ? 0x0d is p o i v u t r e p r es e n q u a n ti t y i s n e g a t i . t r e n o ti m e d e la y i the phas e co r r e c t i o n is i n t h e op p o si t e dir e phas e er r o r . phase co r r ec tio n () = ? ( phc a l ? 0 x 0 d p e r c a libr a ting p h as e u s ing a r e fer e n c e met e r ex am p l e a p o we r f a c t or of 0 . 5 i n d u c t ive c a n b e a s su me d i f t h e output r a te of t h e re f e re nc e me te r i s h a l f of it s p f r then, t h e p e r c e n t er r o r b e tw e e n cf an d t h e pu ls e o u t p u t o i o d 360 (57) pu l s e = 1 a te. f r c a t h e r e fer e n c e met e n b e us e d t o p e r f o r m t h e p r e c e d in g calc u l a t io n s . write phcal value to the phcal register: addr. 0x10 measure the % error between the cf output and the reference meter output set i test = i b , v test = v nom , pf = 0.5 04481-a -089 calculate phcal. see equation 55. f i gure 75. ca lib r a ti ng p h as e u s i n g a r e ferenc e meter f o r t h i s e x a m ple: cf %e rr or a t p f = 0. 5 i n d u c t iv e: % erro r cf ( ib , p f = 0 . 5 ) = 0. 215 % p e ri o d reg i ster re a d in g : pe r i od = 8959 then ph cal is 11 usin g e q ua t i o n s 57 t h r o ug h 59: er r o r = 0.215 %/100 = 0.00215 phase e r r o r () = ?ar c sin ? = ? ? ? ? ? ? ? ? 07 . 0 3 00215 . 0 phc a l = i n t ? ? ? ? ? ? ? 360 8959 07 . 0 + 0x0d = ?2 + 13 = 11 p h ca l can b e exp r es s e d as fol l o w s: phc a l = int ? ? ? ? ? ? ? ? ? ? ? ? ? 2 3 100 % arcsin period error + (58) ? ? ? ? 0x0d n o t e t h a t p h cal is a sig n e d , tw os co m p lem e n t r e gis t er . s e t t in g t h e p h cal r e g i s t er t o 11 p r o v ides a phas e co r r e c t i o n o f 0.08 t phase co r r ec tio n () = ? o co r r ec t the p h as e le ad: period phcal ? 360 ) 0x0d ( phase co r r = ? 08 . 0 8960 360 ) 0x0d 11 ( ec tio n () = ?
ade7763 rev. a | page 41 of 56 i th an acc u r a te sour ce ex am ple c a libr a ting p h as e w w i t h an acc u ra te s o ur ce, li ne c y cle acc u m u la t i o n is a go o d m e t h o d o f c a lib r a t in g phas e er r o r . th e val u e o f l a e n er gy m u s t be ob ta in e d a t tw o p o w e r f a c t o r s, p f = 1 a n d p f = 0.5 ind u c t iv e . set half line cycles for accumulation in linecyc register addr. 0x1c set i test = i b , v test = v nom , pf = 0.5 c a l c u l a t e p h c a l . s e e e q u a t i o n 5 5 . set mode for line cycle accumulation addr. 0x09 = 0x0080 enable line cycle accumulation interrupt addr. 0x0a = 0x04 read line accumulation energy addr. 0x04 reset the interrupt status read register addr. 0x0c i n t e r r u p t ? no no yes yes reset the interrupt status read register addr. 0x0c interrupt? write phcal value to the phcal - 090 f o r t h is exa m ple: l i ne f r e q u e nc y : f = 50 h z to r : cfden = 489 ba se c u rr e n t: i b = 10 a h a l f linecy c ib = 2 000 p e ri d reg i ster : pe r i od = 8959 expect ed li n e a c cu m u l a ti o n a t u n i t y p o w e r f a ct o r (f r o m w a t t ga i n e c t ion): la e n e r g y ib ( ex p e ct e d ) = 19186 a c ti e n erg y readin g a t p f = 0.5 ind u c t i v e: la e n e r g y ib , p f = 0.5 = 9613 register: addr. 0x10 04481-a f i gure 76. c a lib r a ting p h ase with an ac cur a te s o urc e me t e r c o n s t a n t : me t e r c o n s t a n t (im p /w h) = 3.2 lin e v o l t a g e : v nom i nal = 220 v l cf n u m e r a t o r : cf nu m = 0 cf d e n omin a l i ne cy c l e s u s e d a t b a s e cu r r e n t : o s v e the er r o r usin g e q ua t i on 52 is er r o r = 0021 . 0 2 19186 2 19186 9613 = ? phase e r ? = ? ? ? ? ? ? ? ? 07 . 0 3 0021 . 0 r o r () = ?ar c sin u s in g e q u a t i on 55, ph ca l is 1 1 . phc a l = in t 11 13 2 0x0d 360 8959 07 . 0 = + ? = + ? ? ? ? ? ? ? n o t e t h a t p h cal is a sig n e d , tw os co m p lem e n t r e gis t er . t h e p h a s e le a d is co rr ect e d b y 0.08 d e gr ee s wh en t h e p h c a l r e g i s t er is s e t t o 11: n () = ? phase co r r ec tio period phcal ? 360 ) 0x0d ( phase co r r ec tio n () = ? = ? 08 . 0 8960 360 ) 0x0d 11 ( vr ms an d ir ms c a lib ratio n v r m s a n d irm s a r e c a l c ula t ed b y sq u a r i n g t h e i n p u t in a dig i t a l m u l t i p lier . ) 2 cos( ) sin( v 2 ) sin( v 2 ) ( t t v 2 = t v v t 2 2 ? = (59) the s s val u e is ext r ac t 2 a ss f i l t er t o f t h e ou t p u t o s t h e r m s va l u e . an o f fs et co r r e c t i o n is p r o v ide d t o ca nce l n o is e t . ther o is e f r o m t h e 2 t e r m b e c a us e t h e lo w-p a s s f i l t er do es n o t c o m p lete ly a t t e n u a t e t h e sig n al. this n o is e ca n b e m i n b y s y n c h r o n i z i n g th e rm s r e g i s t e r r e a d i zer o cr os sin g o f t h e v o l t a g e sig n al. th e ir q q ua r e o f t h e r m e d f r o m v ( t ) b y a lo w-p . th e s q ua re r o o f t h is lo w- p a s s f i l t er g i v e an d of f s e t c o n t r i but i ons f r om t h e i n p u e is r i p p le n i m i z e d n g s w i th t h e output c a n b e al. n g s o f t h e v o l t a g e i n p u t. co nf igur e d t o i n dic a t e t h e zer o cr os sin g o f t h e vol t a g e sig n this f l o w cha r t de m o n st ra tes ho w vrms and i r ms r e adi n gs a r e syn c hr o n ize d t o t h e zer o cr os s i
ade7763 rev. a | page 42 of 56 2 1 2 2 2 1 2 2 2 2 2 1 irms i 1 set interrupt enable for zero irmsos = i i irms i ? ? 32768 (63) w h e and irms 2 a r e r m s r e g i s r v a l u es wi t h o u t o f fs et co r r ec tio n f o r in p u t i 1 and i 2 , r e s p ec ti ve l y . a p p a p p a r e n t e n erg y ga in ca l i b r a t ion is p r o v ide d fo r b o t h met e r - t o - g t h e v a h / ls b co n s tan t . v a energy = crossing addr. 0x0a = 0x0010 reset the interrupt status read register addr. 0x0c r e irms 1 t e interrupt? no yes 04481- a- 091 read vrms or irms addr. 0x17; 0x16 reset the interrupt status read register addr. 0x0c f i g u re 77. sy nch r o n iz ing v r m s a n d ir m s r e ad ing s wit h zer o c r os s i ng s v o lt age r m s c o m p e n s a t i on i s d o ne af te r t h e s q u a re ro ot . vrm s = vrm s 0 + vrm s os (60) wher e: vrm s 0 i s t h e r m s m e a s u r em en t w i th o u t o f fse t co rr ecti o n . vrm s is lin e a r f r o m f u l l -s cale to f u l l -s cale/20. t o calib r a t e t h e o f fs et, tw o vr ms m e as ur e m e n ts a r e r e q u ir e d , fo r ex am pl e, a t v no mi nal and v no mi nal /10. v no mi nal is set a t half o f t h e f u l l -s cale a n alog in p u t ra n g e s o tha t t h e smal lest lin e a r vrms r e ading is a t v no mi nal /10. vrm s os = a r e n t energy m e t e r ga in ad j u s t m e n t an d f o r set t in ? ? ? ? ? ? + 12 2 1 1 vagain vadiv vaenergy initial (64) t io n . i t u s e d t o cal i b r a t e in divid u a l m e t e r s . a p p i o n s h ou l d b e p e r f or me d b e f r m s t h e m o s t ef f i ci e n t us e o f t h e c r e n t t e s t po i n t s . a p pa r e n t en e r g y g a i n a n d w a t t g a in c o m p e n sa ti o n r e q u s and wa t t o f fs et c o r r e c t i o n e q u ir e a lo w e r t e s t c u r r en t. a p p a r e n t en er g y ga in c a lib r a t io n c a n be t t - h o u r ga i n ca l i b r a t io n l i n e c y cle acc u m u l a t i o n a p p a r e n t e n erg y r e g i s t ers, a r e b o t h r e ad fol l o w ing t h e l i n e c y cle acc u m u la t i on in ter r u p t. f i gure 78 sh o w s a f l o w cha r t fo r ca li b r a t in g ac t i v e and a p pa va d i v is sim i lar t o th e cfd e n f o r th e wa t t -h o u r calib r a sho u l d b e t h e s a me acr o ss al l me t e rs and de ter m ine s t h e v a h/ls b co n s tan t . va g a i n i s a re n t e n e r g y g a i n c a l i br a t o re o f fs et co r r e c t i o n t o m a k e u r ir e t e st in g a t i b , whi l e r m r do ne sim u lt an e o usly wi t h t h e wa u s i ng l i ne c y cl e a c c u m u l a t i o n . in t h i s c a s e , la e n e r g y an d lv a e n e r g y , t h e r e n t en e r g y s i m u l t a n eo u s l y . 1 2 2 2 1 v v vrms v vrms v ? ? 1 ( 6 1 ) wher e vrm s 1 and vrm s 2 a r e r m s r e g i s t er va l u es wi t h o u t o f fs e t co r r ec tio n f o r in p u t v 1 an d v 2 , r e s p ec ti ve l y . i f t h e ra n g e o f t h e 12- b i t, tw os co m p le m e n t v r msos r e g i s t er is n o t e n o u g h , us e t h e v o l t a g e channe l o f fs et r e g i st er , ch2os, t o co r r e c t t h e v r m s o f fs et. c u rr e n t rm s c o m p en sa ti o n i s pe rf o r m e d be f o r e th e sq u a r e r o o t : irms 2 = irms0 2 + 32768 ir msos (62) u t o f fs et co r r e c t i o n . a u l a n m f u l l s c ale t o f u l l t s a r e r e q u ir e d , a t a l f o f th e f u l l -s cale s r e adin g is a t va g a i n = int ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 12 ) ( ) ( 2 1 nominal ib expected ib lvaenergy lvaenergy ( 6 5 lv a e n e r g y ) ib ( expe ct e d ) = int ? ? ? ? ? ? ? ? ? ? ? ) ( s/h 3600 s time on accumulati constant lsb vah i v b nominal ( 6 ? 6 ) a c c o r d i n g t o e q ua tion 34. the va h r e p r es en t e d b y t h e v a ener gy r e g i s t er is va h = v a energy va h / ls b c o n s ta n t (67) the va h / l s b co n s ta n t c a n be v e ri f i e d usin g t h is e q ua t i o n : t h e a c c u m u l a t i on t i me i s d e te r m i n e d f r om e q u a t i o n 3 3 , a n d th e l i n e pe ri od c a n b e d e t e rm i n ed fr o m th e p e ri od r e g i s t e r wher e irms 0 is t h e r m s me as urem e n t wi t h o the c u r r en t r m s c l c t io i s l i ne a r f r o s c ale/100. t o calib r a t e t h is o f fs et, tw o irm s m e a s ur emen fo r ex am pl e, a t i b and i max /50. i max i s s e t h a n alog in p u t ra n g e so tha t t h e sm al les t l i n e a r i r m i max /50. lvaenergy s time on accumulati va constant lsb vah 3600 ) ( = (68)
ade7763 rev. a | page 43 of 56 calculate cfden value for design write cfden value to cfden register addr. 0x15 = cfden set half line cycles for accumulation in linecyc register addr. 0x1c set i test = i b , v test = v nom , pf = 1 c a l c u l a t e w g a i n . s e e e q u a t i o n 4 3 . set mode for line cycle accumulation addr. 0x09 = 0x0080 enable line cycle accumulation interrupt addr. 0x0a = 0x04 r e a d l i n e a active energy: addr. 0x04 apparent energy: addr. 0x07 c c u m u l a t i o n e n e r g y reset the interrupt status read register addr. = 0x0c interrupt? n o yes r e s e t t h e i n t e r r u p t s t a r e a d r e g i s t u s t e r a d d r . = 0 x 0 c no interrupt? yes write wgain value to addr. 0x12 04481-a - 092 c a l c u l a t e v a g a i n . s e e e q u a t i o n 6 5 . w r i t e v g a i n v a l u e t o a d d r . 0 x 1 a f i gure 7 8 . a c ti v e / a p p ar e n t i n t h a d e 7 7 6 3 a r e s h c y i s 5 m h z, va r i o u s timin g a n d f i l t er c h a r ac t e r i s t ics wil l e q uenc y acco r d in g t o t h e fol l o w in g e q ua t i on: g a i n c a l i b r a tio n clkin freq uency i s da t a sh e e t, t h e c h a r ac t e r i s t ics o f t h e o w n when clki n f r eq uen c y eq u a ls 3.579545 mh z. h o w e v e r , t h e ad e7763 is desig n e d t o ha v e t h e s a me acc u rac y a t an y clki n fr e q u e n c y w i th i n th e s p e c i f i e d ra n g e . i f th e c l k i n fr e q u e n n o t 3 . 5 7 9 5 4 n e e d to b e r e def i n e d wit h t h e ne w cl ki n f r e q uen c y . f o r e x a m p l e , th e c u t o ff fr e q u e n c i e s o f a l l d i g i ta l fi l t e r s , s u c h a s l p f 1 , l p f 2 , or h p f 1 , sh i f t i n prop or t i on to t h e c h ange i n clki n f r m h z frequency new 579545 . 3 frequency clkin frequency original = (69) the cha n g e in clki n f r e q uenc y do es n o t a f fe c t t h e t i min g cha r ac t e r i s t ics of t h e s e r i al i n t e r f ace b e c a us e t h e da t a t r a n sfer is e v e r , i t is e r e a d /w ri t e tim i n g o f th e se rial d a ta t r a n l e 2. t a b l e 8 l i y . t a b l e 8. frequen c y d e penden c ie s of th e a d e7 763 pa ra met e rs parameter clkin dependency syn c hr o n ize d wi th t h e s e r i al c l o c k signal (sclk). h o w i m po r t a n t t o o b se r v e th sfer s e e t h e t i min g cha r ac ter i st ics in t a b s t s v a r i ou s t i mi ng ch ange s t h a t are af fe c t e d b y c l k i n f r e q u e nc nyq u ist freq uency for ch 1, ch 2 adc s c l k i n / 8 phcal resoluti on (secon ds p e r lsb) 4/clkin active e n ergy regist er upd a te rate (hz) c l k i n / 4 waveform sam p ling rate (per second) wavsel 1,0 = 0 0 clkin/128 0 1 clkin/256 1 0 clkin/512 1 1 clkin/1024 maximum zxtout period 524,288/clkin
ade7763 rev. a | page 44 of 56 suspending func tionality the a n a l o g an d t h e dig i t a l c i r c u i t can b e susp e n de d s e p a r a tely . t h e ana l o g p o r t ion can b e su sp e n de d b y s e tt ing t h e a s u s p e n d b i t (b i t 4) o f th e m o de r e gis t er to logic highse e the m o d e r e g i s t e r ( 0 x 0 9 ) s e c t ion. i n su sp e n d mo d e , a l l w a ve for m s a m p l e s f r o m t h e a d cs a r e s e t t o 0s. the dig i t a l c i r c ui t r y ca n b e halt e d b y s t o p p i n g t h e c l k i n in p u t a n d m a in ta i n in g a logi c h i gh o r lo w o n t h e clkin p i n. th e ade7763 ca n be r e ac ti va t e d b y r e st o r in g t h e c l kin in p u t and s e t t in g t h e as us pe nd b i t t o log i c lo w . checksum register the ad e7763 has a c h ec ks u m reg i s t er (checks u m[5:0]) t o ens u re t h a t t h e da t a b i t s r e ce i v e d i n t h e las t s e r i al re ad op er a t ion a r e n o t co r r u p t e d . th e 6 - b i t ch e c ks u m r e g i s t er i s r e s e t b e fo r e t h e f i rst b i t (msb o f t h e r e g i st er t o b e r e ad) is pu t o n t h e d o ut p i n . du rin g a seri al r e ad o p e r a t io n , wh en ea ch da ta b i t be co m e s a v a i la b l e u p o n t h e r i sin g e d g e of sclk, t h e b i t i s adde d t o t h e ch e c ks u m r e g i s t er . a t t h e e n d o f t h e s e r i al r e ad o p era t ion, t h e co n t en t o f t h e ch eck s um r e gi s t er i s eq u a l t o t h e s u m o f all o n e s p r e v io us ly r e ad in t h e r e g i s t er . u s in g t h e ch e c ks um r e g i st er , t h e us er ca n det e r m ine if an er r o r has o c c u r r e d d u r i n g t h e las t r e ad o p era t io n. n o t e tha t a r e ad t o t h e ch ecks um r e gis t er also gen e r a tes a ch e c ksu m o f t h e che c ksu m r e g i ster i t s e lf. content of register (n-bytes) checksum register addr: 0x3e + + dout 04481-a - 070 f i gure 79. che c ks um r e g i s t er f o r s e ri a l inter f a c e r e ad serial interface al l ad e7763 f u n c tio n ali t y is ac ces s i b le via s e v e ral o n -c hi p r e g i s t erss e e f i gur e 80. th e con t e n ts o f t h es e reg i s t ers can b e u p da te d o r r e ad usin g t h e o n -chi p s e r i a l i n ter f ace. af ter p o w e r - on or to g g l i n g t h e res e t p i n lo w an d a fa l l i n g e d ge on cs , th e ad e7763 is p l aced in co mm unica t io n m o de . i n co tio n m o de , t h e ad e7763 exp e c t s a wr i t e t o i t s c o mm unica t io n t o t h e co mm unic a t io n r e g i s t er mm unica - r e g i s t er . th e da t a wr i t t e n det e r m i n es w h e t h e r t h e n e xt da t a t r a n sfer o p era t io n is a r e ad or a wr i t e and w h i c h r e g i s t er is ac ces s e d . th er efo r e , al l da t a tra n sf er o p era t io n s wi th t h e ad e7763, whet her a r e ad o r a wr i t e , m u s t b e g i n wi t h a wr i t e to t h e co mm uni c a t ion r e g i s t er . communication register in out in out in out in out in out register 1 register 2 register 3 register n ? 1 register n register address decode din dout 04481-a - 071 f i gur e 8 0 . a ddr essing ade7 76 3 regi ster s via the comm uni c a t io n reg i st er the co mm uni c a t io n r e g i s t er is a n 8- b i t - wide r e g i s t er . th e ms b det e r m i n es w h e t h e r t h e n e xt da t a t r a n sfer o p era t io n is a r e ad or a wr i t e . th e 6 l s bs co n t ain t h e addr es s o f t h e reg i s t er t o b e access e d s e e t h e c o mm uni c a t io n reg i ster s e c t io n fo r a m o r e det a i l e d de s c r i pt io n. f i gur e 81 an d f i gur e 82 sh o w t h e da ta tran sf er s e q u en ces f o r a re a d a n d w r ite op e r a t i o n , re sp e c t i vely . u p on c o m p l e t i on of a da ta tra n sf er (r ead o r wr i t e), t h e ad e7763 a g a i n en t e rs t h e co mm unic a t io n m o de . a da t a t r a n sfer is co m p let e w h e n t h e ls b o f th e ad e 7763 r e g i s t er bein g addr es s e d (f o r a wr i t e o r a r e ad) is tra n sf er r e d t o o r f r o m th e ad e7763. multibyte communication register write din sclk cs dout read data address 0 0 04481- a- 072 f i g u re 81. r e ad ing d a t a f r o m t h e a d e 7 7 6 3 v i a t h e s e ri al i n ter f ac e communication register write din sclk address 0 1 cs 0 4 4 8 1 - 073 multibyte read data f i g u re 82. w r it ing d a t a t o t h e a d e 7 7 63 v i a th e s e r i a l i n ter f ace a-
ade7763 rev. a | page 45 of 56 a d e u p o f f o ur sig n als : the s e r i al in ter f ace o f the ad e 7 7 6 3 i s m sclk, d i n, d o ut , an d cs . th e s e r i al clo c k fo r a da t a t r a n s f e r is a ppl ie d a t t h e s c lk l o g i c i n put. t h i s l o g i c i n pu t ha s a s c h m itt - t r ig ger in p u t st r u c t ur e t h a t a l lo ws slo w r i sing and fa l l i n g clo e d g e s t o b e us e d . al l da t a t r a n s f er o p era t io n s ar e syn c hr o n i z e d t o th e s e r i al c l o c k. da ta is s h if ted in t o t h e ade7763 a t t h e d i n logic in p u t u p o n t h e fal l i n g e d ge o f sclk. d a t a is s h if t e d o u t o th e ad e7763 a t th e d o ut log i c o u t p u t u p o n a r i sin g edg e o sclk. th e c k f f cs log i c in p u t is t h e ch i p -s e l e c t in pu t. this i n p u t i s u s ed wh e n m u l t i p le d e vi ce s s h a r e th e se rial b u s. a fallin g ed g e up on cs als o r e s e ts th e s e r i al in in t o co mm unic a t io n m o de . t t e r f ace an d places th e ad e7763 h e cs in p u t sh o u l d be dr i v en lo w fo r t h e en t i r e da t a t r a n sfer o p era t io n. b r i n g i n g cs hig h d u r i n g a da t a t r a n sfer o p era t io n ab o r ts t h e t r a n sfer a n d places t h e s e r i a l b u s in a hi g h im p e dan c e st a t e . th e cs logic in p u t c a n b e tie d lo w if t h e ad e7 763 is t h e onl y de vic e on t h e s e r i al b u s. h o wever , wi t h cs tied lo w , a l l ini t ia t e d da t a tra n sf er o p era t io n s m u s t be f u l l y com p l e te d , i.e., t h e ls b o f e a ch reg i st er m u st b e t r an sfer r e d b e c a u s e t h ere is n o ot h e r wa y t o b r ing t h e ad e7 763 in t o c o mm u - n i c a t i on mo d e w i t h out re s e tt i n g t h e e n t i re d e v i c e u s i n g res e t . ade7763 seri al write operation the s e r i al wr i t e s e q u e n ce t a k e s place as fol l o w s. w i t h t h e ad e7763 in comm unic a t io n m o de (i . e ., t h e cs in p u t l o g i c lo w), f i rs t a wr i t e t o t h e co mm unic a t io n r e g i s t er o c c u rs. the ms b of th i s b y t e tra n s f e r i s a 1, in d i ca t i n g th a t t h e d a ta tra n s f e r o p era t ion is a wr i t e . the ls bs of t h is b y t e co n t ain t h e addr es s o f th e reg i s t er t o b e wr i t ten to . the ad e7763 s t a r ts s h if t i n g in t h e r e gis t er da t a u p o n t h e n e xt fal l i n g edg e o f sclk. al l r e m a ining b i ts o f r e gist er da ta a r e s h if ted in u p o n t h e fal l i n g edg e o f s u b s e q u en t scl k p u ls ess e e f i gur e 83. a s expla i n e d e a rlier , t h e da t a wr i t e is ini t i a t e d b y a wr i t e t o t h e comm uni c a t io n r e g i s t er fol l o w e d b y t h e da t a . d u r i n g a da t a wr i t e o p era t io n, da t a is t r a n sfer r e d t o al l o n -chi p r e g i s t ers o n e b y t e a t a t i m e . af t e r a b y te is t r a n sfer r e d in t o t h e s e r i al p o r t , t h er e is a f i ni te tim e bef o r e i t is tra n sf er r e d t o o n e o f t h e ad e7763 o n -c hi p r e gis t er s. al t h o u gh an o t h e r b y te tra n sf er t o th e ser i al p o r t ca n st a r t w h i l e t h e pr e v io us b y t e is b e in g t r a n sfer r e d t o a n o n -chi p r e gi s t e r , th i s se co n d b y t e tra n s f e r s h o u ld n o t f i ni s h un til a t lea s t 4 s a f t e r t h e en d o f t h e p r e v i o us b y t e tra n s f er . th i s fun c t i o n ali t y is exp r ess e d i n t h e t i mi n g sp e c if ica t io n t 6 see f i gur e 83. i w f a r i t e o p era t io n is a b o r t e d d u r i ng a b y te t r a n sfer ( cs is b r o u g h t h i g h ), t h en tha t b y te ca nn o t b e w r i t t e n t o t h e d e s t ina t io n r e gister . d e st ina t ion r e g i st ers can b e u p to 3 b y t e s w i de s e e t a b l e 9, t a b l e 10, t a b l e 11, t a b l e 12, and t a b l e 13. th erefo r e t h e f i rs t b y te shi f te d i n to t h e s e r i a l p o r t a t di n i s t r ans f e r re d to t h e m s b (m o s t s i g n if i c an t b y t e ) o f t h e de st i n a t i o n reg i s t er . i f , fo r exam ple, 3 t h e addr es s e d r e g i s t er is 12 b i ts wi de , a 2 - b y t e da t a t r a n sfer m u s t take p l ac e . b e ca use t h e da t a is al wa ys as s u m e d t o be r i g h t j u s t if ie d , in this case t h e 4 ms bs o f th e f i r s t b y t e w o uld b e ig n o r e d a n d t h e 4 ls bs o f th e f i rs t b y te wr i t t e n t o th e ad e 7 7 6 w o u l d b e t h e 4 ms bs o f th e 12 -b i t w o rd . f i gur e 84 il l u s t ra t e s th i s e x a m p l e . din sclk t 2 t 3 t 4 t 5 command byte 10 a4 a5 a3 a2 a1 a0 cs t 1 t 7 t 6 t 8 most significant byte least significant byte db7 db0 db7 db0 t 7 04481-a - 074 inter f ace wri t e t i mi n g f i gure 83. s e ri al sclk din x x x x db11 db10 db9 db8 db7 db6 db5 db4 db3 db2 db1 db0 most significant byte least significant byte 04481-a - 075 f i gure 84. 1 2 -bit s e ri al w r ite o p er ati o n
ade7763 rev. a | page 46 of 56 serial r e ad o p er ation dur i n g a da ta r e ad o p er a t io n f r o m t h e ad e776 3, da ta is s h if t e d out a t t h e d o u t l o g i c output up on t h e r i s i ng e d ge of s c l k . as is t h e cas e wi t h t h e da t a wr i t e op era t ion, a wr i t e t o t h e co mm u - n i ca ti o n r e gis t er m u s t p r eced e a d a t a r e a d . w i t h t h e ad e7 763 in co mm unica t io n m o de ( cs lo g i c l o w) , f i rs t a n 8- b i t wr i t e t o t h e co mm unic a t io n r e g i s t er o c c u rs. th e ms b o f this b y te tra n sf er is a 0, indica t i n g tha t t h e n e xt da t a t r a n sfer o p era t io n is a r e ad . the ls bs o f t h is b y t e co n t ain t h e addr es s o f t h e reg i s t er tha t is t o be r e ad . the ad e7763 s t a r ts sh i f t i ng d a t a out of t h e re g i ste r up on t h e ne x t r i s i ng e d ge of sclkse e f i gur e 85. a t this p o in t, t h e d o ut logic o u t p u t le a v es i t s hi g h i m p e dan c e s t a t e a n d s t a r ts dr iv i n g t h e da t a b u s. a l l re m a i n i n g bit s of re g i ste r d a t a are sh i f te d out up on s u b s e - q u en t sclk ri sin g e d g e s. th e serial in t e r f ace als o en ter s co mm u- nica tio n m o de as so o n as t h e r e ad is co m p let e . t h en, t h e d o ut log i c o u t p u t e n ters a hig h i m p e dan c e s t a t e u p o n t h e fal l i n g e d ge o f th e las t sclk p u ls e . th e r e a d o p er a t io n can b e ab o r te d b y br i n g i n g t h e cs lo gic in p u t high b e f o r e th e da t a tr a n sf e r i s co m p let e . th e d o ut ou t p u t e n t e rs a hig h i m p e dan c e s t a t e up on t h e r i s i ng e d ge of cs . w h en an ad e7 763 r e g i s t er is addr es s e d f o r a r e ad o p er a t i o n , t h e en t i r e co n t e n ts o f t h a t r e g i s t er a r e t r a n sfer r e d t o t h e s e r i a l p o r t . this al lo ws th e ad e7763 t o m o dif y i t s on-c hi p r e g i st e r w i th o u t th e ri s k o f c o rr u p ti n g d a ta d u ri n g a m u l t i b y t e tr a n s f e r . n o t e t h a t w h en a r e ad o p era t ion fol l o w s a wr i t e o p era t ion, t h e r e ad co mmand (i .e ., wr i t e t o comm unic a t io n r e g i s t er) s h o u l d n o t ha p p e n fo r a t le as t 4 s a f t e r t h e e n d o f t h e wr i t e o p era t io n. i f t h e r e ad comma n d is s e n t wi t h in 4 s o f t h e wr i t e o p era t io n, t h e last b y te o f t h e wr i t e o p er a t i o n co u l d b e los t . this t i ming co n s t r a i n t is g i ven as t i min g sp e c if ica t ion t s 9 . sclk cs t 1 t 10 t 13 db0 db7 db0 db7 t 11 11 0 0 a4 a5 a3 a2 a1 a0 din dout t t 12 command byte most significant byte least significant byte t 9 04481-a - 076 f i g u re 85. s e ri al int e r f ace r e ad ti ming
ade7763 rev. a | page 47 of 56 descr registers table 9. summary of registers by address address name r/w no. bits default type 1 iption 0x01 waveform r 24 0x0 s wavef wavef 1, channel 2, or the active power signal. selecte sampl orm register. this read-only register contains the sampled orm data from either channel the data source and the le ngth of the waveform registers are d by bits 14 and 13 in the mode registersee the channel 1 ing and channel 2 sampling sections. 0x02 aenergy r 24 0x0 s active time in section. energy register. active power is accumulated (integrated) over this 24-bit, read-only re gistersee the energy calculation 0x03 raenergy r 24 0x0 s same a follow s the active energy register, exce pt that the register is reset to 0 ing a read operation. 0x04 laenergy r 24 0x0 s line a power numbe ccumulation active energy register. the instantaneous active is accumulated in this read -only register over the linecyc r of half line cycles. 0x05 vaenergy r 24 0x0 u appar ulated over time in this read-only re ent energy register. apparent power is accum gister. 0 x06 rvaenergy r 24 0x0 u same as the vaenergy register, except that the register is reset to 0 following a read operation. 0x07 lvaenergy r 24 0x0 u line accumulation apparent energy register. the instantaneous real power is accumulated in this read -only register over the linecyc number of half line cycles. 0x08 reserved 0x09 mode r/w 16 0x000c u mode register. this is a 16-bit register through which most of the ade7763s functionality is accessed. signal sample rates, filter enabling, and calibration modes are selected by writing to this register. the contents can be read at any timesee the mode register (0x09) section. 0x0a irqen r/w 16 0x40 u interrupt enable register. ade7763 interrupts can be deactivated at any time by setting the corresponding bit in this 16-bit enable register to logic 0. the status register continues to detect an interrupt event even if disabled; however, the irq output is not activatedsee the interru ts p section. 0x0b status r 16 0x0 bit read-only register that contains information regarding the source of ade7763 interruptssee the interrupts section. u interrupt status register. this is a 16- 0x0c rststatus r 16 0x0 u same as the interrupt status register, except that the register contents are reset to 0 (all flags cleared) after a read operation. 0x0d ch1os r/w 8 0x00 s * channel 1 offset adjust. bit 6 is not used. writing to bits 0 to 5 allows offsets on channel 1 to be removed see the analog inputs and ch1os register sections. writing logic 1 to the msb of this register enables the digital integrator on channel 1; writ ing logic 0 disables the integrator. the default value of this bit is 0. 0x0e ch2os r/w 8 0x0 s * channel 2 offset adjust. bits 6 and 7 are not used. writing to bits 0 to 5 of this register allows offsets on cha nnel 2 to be removedsee the analog inputs section. note that the ch2os register is inverted. to apply a positive offset, a negative number is written to this register. 0x0f gain r/w 8 0x0 u pga gain adjust. this 8-bit register is used to adjust the gain selection for the pga in channels 1 and 2see the analog inputs section. 0x10 phcal r/w 6 0x0d s phase calibration register. the phase relationship between channel 1 and 2 can be adjusted by writing to this 6-bit register. the valid content of this twos complement register is between 0x1d to 0x21. at the line frequency of 60 hz, this ranges fr om C2.06 to +0.7?see the phase compensation section. 0x11 apos r/w 16 0x0 s active power offset correction. this 16- bit register allows small offsets in the active power calculation to be removedsee the active power calculation section.
ade7763 rev. a | page 48 of 56 r/w no. bits default type 1 description address name 0x12 wgain r/w 12 0x0 s power gain adjust. this is a 12-bit register. calibrate the active power calculation by writing to this regist er. the calibration range is 50% of ll-scale active power. the resolution of the gain adjust is the nominal fu 0.0244%/lsb see the calibrating an energy meter section. 0x13 wdiv r/w 8 0x0 u gy active energy divider register. the internal active energy register is divided by the value of this register before being stored in the aener register. 0x14 cfnum r/w 12 0x3f u just the output frequency cf frequency divider numerator regi ster. ad on the cf pin by writing to this 12-bit read/write registersee the energy-to-frequency conversion section. 0x15 cfden r/w 12 0x3f u ency divider denominator register. adjust the output e nversion section. cf frequ frequency on the cf pin by writing to this 12-bit read/write registerse the energy-to-frequency co 0x16 irms r 24 0x0 u channel 1 rms value (current channel). 0x17 vrms r 24 0x0 u channel 2 rms value (voltage channel). 0x18 irmsos r/w 12 0x0 s ction register. channel 1 rms offset corre 0x19 vrmsos r/w 12 0x0 s channel 2 rms offset correction register. 0x1a vagain r/w 12 0x0 s apparent gain register. calibrate the apparent power calculation by writing to this register. the calibration range is 50% of the nominal scale real power. the resolut full- ion of the gain adjust is 0.02444%/lsb. 0x1b vadiv r/w er 8 0x0 u apparent energy divider register. the internal apparent energy regist is divided by the value of this register before being stored in the vaenergy register. 0x1c linecyc r /w xffff u line-cycle register. this 16-bit et the 16 0 line cycle energy accumulation mode register is used during line cycle energy accumulation mode to s number of half line cycles for energy accumulationsee the line cycle energy accumulation mode section. 0x1d zxtout r/w 12 0xfff u e zero-crossing timeout. if no zero crossings are detected on channel 2 within the time specified in this 12-bi t register, the interrupt request lin ( irq ) will be activatedsee the zero-crossing detection section. 0x1e sagcyc r/w 8 0xff u e sag output is activated see the line voltage sag detection sag line cycle register. this 8-bit register specifies the number of consecutive line cycles below saglvl that is required on channel 2 before th section. 0x1f saglvl r/w 8 0x0 u peak nel 2 the sag sag voltage level. an 8-bit write to this register determines at what signal level on chan pin becomes active. the signal must remain low for the number of cycles specified in the sagcyc register before the sag pin is activatedsee the line voltage s ag detection section. 0x20 ipklvl r/w 8 0xff u channel 1 peak level threshold (current channel). this register sets the level of current peak detection. if th e channel 1 input exceeds this level, the pki flag in the status register is set. 0x21 vpklvl r/w 8 0xff u channel 2 peak level threshold (voltage channel). this register sets the level of voltage peak detection. if th e channel 2 input exceeds this level, the pkv flag in the status register is set. 0x22 ipeak r 24 0x0 u channel 1 peak register. the maximum input value of the current channel, since the last read of the register is stored in this register. 0x23 rstipe ak r 24 0x0 u same as channel 1 peak register, except that the register contents are reset to 0 after a read. 0x24 vpeak r 24 0x0 u channel 2 peak register. the maximum input value of the voltage channel, since the last read of the register is stored in this register. 0x25 rstvpeak r 24 0x0 u e same as channel 2 peak register, except that the register contents ar reset to 0 after a read. 0x26 temp r 8 0x0 s temperature register. this is an 8-bit register that contains the result of the latest temperature conversion see the temperature measurement section.
ade7763 rev. a | page 49 of 56 address name r/w no. bits default type 1 description 0x27 period r 16 0x0 u period of the channel 2 (voltage channel) input estimated by zero- crossing processing. the msb of this register is always zero. 0x28C 0x3c reserved. 0x3d tmode r/w 8 C u test mode register. 0x3e chksum r 6 0x0 u in the previous readssee the serial read operation section. checksum register. this 6-bit, read-onl y register is equal to the sum of all the ones 0x3f dierev r 8 C u die revision register. this 8-bit, read-only register contains the revision number of the silicon. 1 type decoder: u = unsigned, s = signed by twos complement method, and s * = signed by sign magnitude method.
ade7763 rev. a | page 50 of 56 register descriptions all ade7763 functionality is accessed via on-chip registers. each r ister and ansf ring the regis data. full descr tion of the se l int col is given in the serial interface secti on. mu n r t omm egis is an bit, write regist at con processor. all data transfer operations must begin with a write to t r det wheth the n t operation is a read o write designations for the communication register. db7 db6 db5 db4 db3 db2 db1 db0 egister is accessed by first writing to the communication re g then tr er ter a ip ria erface proto com nicatio egis er the c unication r ter 8- -only er th trols the serial data transfer between the ade7763 and the host he communication register. the data written to the communic ation registe ermines er ex r a and which register is being accessed. table 10 outlines the bit w/r 0 a5 a4 a3 a2 a1 a0 table 10. communication register bit location bit mnemonic description 0 to 5 a0 to a5 the 6 lsbs of the communication register specify the regi ster for the data transfer operation. table 9 lists the address of each on-chip register. 6 reserved this bit is unused and should be set to 0. 7 w/r when this bit is a logic 1, the data transfer operation immediately following the write to the communication register is interpreted as a write to the ade7763. when this bit is a logic 0, the data transfer operation immediately following the write to the communication register is interpreted as a read operation. mode register (0x09) the ade7763 functionality is configured by writing to the mode register. table 11 describes the functionality of each bit in the register. table 11. bit location bit mnemonic default value description 0 dishpf 0 hpf (high-pass filter) in channe l 1 is disabled when this bit is set. 1 dislpf2 0 lpf (low-pass filter) after the multipli er (lpf2) is disabled when this bit is set. 2 discf 1 frequency output cf is di sabled when this bit is set. 3 dissag 1 line voltage sag detection is disabled when this bit is set. 4 asuspend 0 by setting this bit to logic 1, both a/d converters can be turned off. during normal operation, this bit should be left at logic 0. all digital func tionality can be stopped by suspending the clock signal at clkin pin. 5 tempsel 0 temperature conversion starts when this bit is set to 1. this bit is automatically reset to 0 after the temperature conversion. 6 swrst 0 software chip reset. a data transfer should not take place to the ade7763 for at least 18 s after a software reset. 7 cycmode 0 setting this bit to logic 1 places th e chip in line cycle energy accumulation mode. 8 disch1 0 adc 1 (channel 1) inputs are internally shorted together. 9 disch2 0 adc 2 (channel 2) inputs are internally shorted together. 10 swap 0 by setting this bit to logic 1, the analog in puts v2p and v2n are connected to adc 1 and the analog inputs v1p and v1n are connected to adc 2. use these bits to select the wa veform register update rate. dtrt1 dtrt0 update rate 0 0 27.9 ksps (clkin/128) 0 1 14 ksps (clkin/256) 1 0 7 ksps (clkin/512) 12, 11 dtrt1, 0 00 1 1 3.5 ksps (clkin/1024)
ade7763 rev. a | page 51 of 56 d e s c r i p t i o n bit location bit mnemonic defau l t v a l u e use these bits t o select the sour ce of the sampled data for the waveform regi ster. wavsel1, 0 length sou r ce 14, 13 wavsel1, 0 00 0 0 24 bits, active power signal (output of lpf2) 0 1 reserved 1 0 24 bits, channe l 1 1 1 24 bits, channe l 2 15 poam 0 w r i t i n g l o g i c 1 to t h i s b i t a llo ws o n l y p o sitive p o w e r to ac c u mulate . the defau l t valu e o f t h i s b i t i s 0. u t p 2 7 . 9 k 0 1 = 1 4 . 4 k 1 0 = 7 . 2 k 1 1 = 3 . 6 k s poam s e l (waveform selection for sample mode) 0 0 00 00 0 0 0 0 1 1 swap (swap ch1 and ch2 adcs) dtrt ( w a v e f o r m s a m p l e s o 0 0 = u t d a t a r a t e ) s p s ( c l k i n / 1 2 8 ) s p s ( c l k i n / 2 5 6 ) s p s ( c l k i n / 5 1 2 ) p s ( c l k i n / 1 0 2 4 ) (positive only accumulation) w a v 00 = lpf2 01 = reserved 10 = ch1 11 = ch2 00 0 0 15 14 13 1 10 9 8 5 4 3 2 addr: 0x09 12 1 7 6 1 0 dishpf (disable hpf1 in channel 1) dislpf2 (disable lpf2 after multiplier) discf dissag (disable sag output) swrst (software chip reset) cycmode a t i o n m o d e ) disch2 c h a n n e l 2 ) (disable frequency output cf) asuspend (suspend ch1 and ch2 adcs) tempsel (start temperature sensing) ( l i n e c y c l e e n e r g y a c c u m u l note: register contents show power-on defaults 04481-a - 077 f i gure 8 6 . mo d e regi st er ( s h o r t t h e a n a l o g i n p u t s o n disch1 ( s h o r t t h e a n a l o g i n p u t s o n c h a n n e l 1 )
ade7763 rev. a | page 52 of 56 p r ( 0 t t a e g i , r u p r s t e r ( 0 the s t a t us r e g i st er is us e d b y t h e m c u t o s o ur ce o f a u p t r e q u i n t e r r u r e s e t i n t s t a t u s e r r u p t s e g i s t e r t u s r x0b), s t e r ( 0 x 0 c ) i n t e r t e n a b l e e g i x0a) de t e r m i n e t h e n in t e r r es t ( ir q ). w h e n a n in t e r r u p t e v en t o c c u rs, t h e c o r r e s p o nd i n g f l ag i n t h e i n te r r u p t st a t u s g i s t e r i s s e t to log i c h i g f t h e e n a b le b i g i s logic 1 in t h e in t er r u pt e n ab l e re g i s t e r , th e ir q re h . i t f o r th is f l a logic o u t p u t wil l g o ac ti ve l o w . w t h e m c u ser v ices t h t e r r u p t, i t m u r e ad f r o m th e in t e r r u p t s t a t us r e g i s t er t o de t e r m i n e t h e s o ur ce o f t h e i n t u p t . a bl e 12 . bit location interrupt flag description h e n e in s t f i r s t c a r r y o u t a e r r t 0 aehf indicates that an interrupt occu rred because the active energy register, aener gy, is more than half full. 1 sag ind i cates that an interrupt was caused by a sag on the line vo lta g e. 2 cycend indicates the end of energy accumulation over an integral num b er of half li ne c y cles, as defined by the content of the linecyc r e gistersee th e line cycle energy accumulati on mode sectio n. 3 wsmp indicates that new data is prese n t in the wavefo r m register. 4 zx this status bit reflects the status of the zx logic ouputsee th e zero-crossing de tection section. 5 temp indicates that a temperature conversion re sult i s available in the temperature register. 6 reset ind i cates the end of a reset for software and har d ware re sets. t h e corresp ond i n g enable bit ha s no function in the interrupt enable regi ster, i.e. , this status bit is set at the end o f a re set, but cannot be enabled to cause an interrupt. 7 aeof indicates that the active energy register has ov e r flowed. 8 pkv indicates that the waveform sa mple from cha n nel 2 has e x cee d ed the vpklvl value. 9 pki indicates that the waveform sample from cha n nel 1 has e x cee d ed the ipklvl value. 10 vaehf indicates that an interrupt occu rred because the apparent energy registe r, vae n ergy, is more than half full. 11 vaeof indicates that the appare nt ener gy register has overflo w ed. 12 zxto indicates that an interrupt was caused by a missing zero cro ssi ng on the line v o ltage for a spe c ified number of line cycle s see the zero-crossi ng t imeout section. 13 ppos indicates that the power has gone from negative to positive. 14 pneg indicates that the power ha s go ne from positive to negative. 15 reserv ed reserved. vaehf (vaenergy is half full) ppos (power negative to positive) reserved pneg (power positive to negative) 00 0 0 0 0 0 00 0 0 00 00 0 8 97 4 5 62 30 1 15 14 13 12 11 10 aehf (active energy half full) sag (sag online voltage) cycend (end of linecyc half line cycles) wsmp (waveform samples data ready) zx (zero crossing) temp (temperature data ready) reset (end of software/hardware reset) aeof (active energy register overflow) zxto (zero-crossing timeout) vaeof (vaenergy overflow) pki (channel 1 sample above ipklvl) pkv (channel 2 sample above vpklvl ) 04481-a - 079 addr: 0x0a, 0x0b, 0x0c f i gure 87. inte rrupt status /i nterr u pt e n abl e r e gister
ade7763 rev. a | page 53 of 56 r . the ms b o f t h is r e g i s t er is us e d t o s w i t ch t h e dig i t a l in teg r a t o r on a n d of f i n of f s e t c o r r e c tio n in cha n ne l 1. t a b l e 13 s u mm a r izes t h e f u nc tio n o f this r e g i ste r . ch1os register (0x0d) the ch1o s r e g i s t er is a n 8- b i t, r e ad/ w r i t e enable d r e g i s t e c h an n e l 1 , a n d bit s 0 to 5 i n d i c a te t h e a mou n t o f ta bl e 13 . ch 1 o s r e gist er bit location bit mnemonic description 0 t o 5 offset the 6 lsbs of the ch1os register control the am ount of dc offset correction in the channel 1 adc. the 6-bit offset correction is sign and ma gnitud e coded. bits 0 to 4 indicate the magnitude of the offset correction. bit 5 shows the sign of the offset correction. a 0 in bit 5 means the offset correct ion is po sitive, a n d a 1 indicates the offset correction i s negative. 6 n o t u s e d t u s e d . t h i s b i t i s n o 7 i n t e g r a t o r t t i n g this bit is used t o activate the digi tal integrator on channel 1. the digita l integrator is switch e d o n b y s e this bit. this bit is set to 0 by def a ult. d i g i t a l i n t e g r a t o r s e l e c t i o n 1 = enable 0 = disable not used 0 0 0 0 00 00 765 4 3210 addr: 0x0d sign and magnitude coded offset correction bits 04481-a - 078 f i g u re 88. cha nne l 1 o f f s et r e g i s t e r
ade7763 rev. a | page 54 of 56 s o u t l i n e d i m e n s i o n 20 11 7. 50 7. 20 6. 90 8. 20 7. 80 7. 40 5. 6 0 5. 3 0 5. 0 0 10 1 co p l anari t y 0. 10 0.05 min 1.85 1 . 7 5 1. 6 5 0.65 bsc 0.25 0.09 0.95 0.75 0.55 8 4 0 2.00 max 0.38 0.22 se a t i n g p l ane pin 1 compliant to jedec standards mo-150ae f i gure 89. 2 0 -l ead shrink sm al l o u t lin e p a ckage [s sop ] (r s-20) di me nsio ns sho w n i n mi ll im e t e r s ordering guide model temperature r a nge package descri ption package option ade7763ars ?40c to +85c 20-lead ssop rs-20 ade7763ars rl ?40c to +85c 20-lead ssop rs-20 eval-ade77 63e b evaluation board
ade7763 rev. a | page 55 of 56 notes
ade7763 rev. a | page 56 of 56 ? 2004 analo g de vices, inc. all rights reserve d . tra d em arks and registered tra d ema r ks are the prop erty of their respective owners . d04481C0C 10/04(a) notes

▲Up To Search▲

Price & Availability of EVAL-ADE7763EB

	To Download EVAL-ADE7763EB Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .