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p-compatible multiplying quad 12-bit d/a converter ad394 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 . s p ecificatio n s subj ec t to ch an 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 four, complete, 12-bit cmos dacs with buff er registers linearity error: 1/2 lsb t min , t ma x (ad3 94t) factory-trimmed gain an d off s et precision output amplifier s fo r v out full four -qu a dr ant multiplicati on per dac monoticity guaranteed over f u ll temper atur e range fast settling: 1 5 s maximum to 1/2 lsb avail a ble in mi l-std-88 3b pro d uc t d e scripti o n the ad394 co n t a i n s f o ur 12-b i t, hig h -sp e e d , lo w p o w e r , v o l t a g e o u t p ut, m u l t i p ly in g dig i t a l - to -ana lo g co n v er ters in a com p ac t 28-p i n h y b r id p a cka g e. t h e desi g n is b a s e d on a p r o p r i et a r y , la t c he d , 12- b i t, cmos d a c chi p , w h ich r e d u ce s chi p co un t and p r o v ides hig h r e lia b ili t y . th e ad394 is ideal f o r sys t em s r e q u ir in g dig i t a l co n t r o l o f ma n y a n alog v o l t a g es w h er e b o a r d sp ace is a t a p r e m i u m an d lo w p o w e r co n s um pt io n is a n e ces- si ty . s u ch a p pl ic a t io n s in cl ude a u t o ma t i c t e st e q ui pm en t, p r o c ess c o n t ro l l e r s , and ve c t or st ro ke d i sp l a y s . the ad394 is las e r - tr imm e d t o 1/2 ls b maxim u m dif f er en tial a nd in t e g r al linea r i t y (ad394t) a nd f u l l -s cale acc u rac y o f 0.05 p e r c en t a t 25c. th e hig h ini t ial acc u rac y is p o s s i b le b e ca us e o f t h e us e o f p r e c isio n, l a s e r - t r im m e d , t h in-f i l m s c a l in g r e sis t o r s. the i n di v i d u al d a c r e g i s t ers ar e acces s e d b y t h e cs1 th r o ugh cs4 co n t r o l p i n s . th es e con t r o l sig n als al lo w a n y co m b ina t ion o f th e d a c s e le c t ma tr ix t o o c c u r (s ee t a b l e 3). on ce s e lec t ed , th e d a c is lo aded wi t h a sing le 12-b i t wide w o r d . th e 12-b i t p a ra l l e l dig i t a l i n p u t i n ter f aces to m o st 12- and 16-b i t b u s sys t em s. the ad394 o u t p u t s (v refin = 1 0 v) p r o v ide a 10 v b i p o la r o u t p ut ra n g e wi t h p o si t i v e -t r u e o f fs et b i na r y in p u t co ding. the ad394 is p a c k a g ed in a 28 -lead cera mic p a c k a g e an d is a v a i la b l e f o r o p era t io n o v er a ? 55c t o +125c t e m p era t ur e ra n g e . f i gur e 1 . f u nctio n al bl oc k dia g r a m produc t highlight s 1. the ad394 o f f e rs a dra m a t ic r e d u c t io n in p r in ted cir c ui t b o ard sp ac e in s y ste m s u s ing m u l t i p l e l o w p o we r d a c s . 2. e a ch d a c is i ndep e n d e n t l y ad dr ess a b l e and pr o v ides ve r s a t i l e c o n t ro l arch ite c tu re f o r a s i m p l e i n te r f a c e to micr o p r o ces s o r s. al l la t c h enable sig n als a r e le v e l - tri g g e r e d . 3. the o u t p u t v o l t a g e is t r imm e d t o a f u l l -s cale ac c u rac y o f 0.05%. s e t t l i n g time t o 1/2 ls b is 15 s maxim u m. 4. a max i m u m ga i n t c o f 5 p p m/ c is achi e v a b l e . 5. t w o- o r f o ur -q uadran t m u l t i p l i ca tion c a n be ac hiev e d s i m p l y by a p p l y i ng t h e appropr i a t e i n pu t vo lt ag e s i g n a l to t h e s e l e c t e d d a c ' s re f e re nc e ( v refin ). 6. the ad394td f e a t ur es gua r an teed acc u rac y and lin e a r i t y o v er th e ?55c t o +125c t e m p era t ur e ra n g e .
ad394 rev. a | page 2 of 12 table of contents specifications ..................................................................................... 3 absolute maximum ratings ............................................................ 5 esd caution .................................................................................. 5 pin configuration and functional block diagram ...................... 6 theory of operation ........................................................................ 7 multiplying mode ......................................................................... 7 data and control signal format ................................................ 7 timing ............................................................................................ 8 analog circuit details ..................................................................8 operation from 12 v supplies ..................................................9 power supply decoupling ............................................................9 improving full-scale stability .....................................................9 applications ...................................................................................9 applications ................................................................................ 10 package outline .............................................................................. 12 ordering guide .......................................................................... 12 revision history 9/04Crev. 0 changed to rev. a updated format ....................................................................... universal deleted ad395 part................................................................ universal change to product description...........................................................1 changes to specifications table............................................................3 delete figure 3 .......................................................................................4 delete figure 6 .......................................................................................5 change to theory of operation section.............................................7 7/85Cinitial version: revision 0
ad394 rev. a | page 3 of 12 specifications table 1. t a = 25c, v refin = 10 v, v s = 15 v, unless otherwise specified ad394td and ad394td/883b 1 model min typ max units data inputs (pins 1-16) 2 ttl or 5 v cmos-compatible input voltage bit on (logic 1) 2.4 5.5 v bit off (logic 0) 0 0.8 v input current 4 40 a resolution 12 bits output voltage range 3 v refin v current 5 ma static accuracy gain error 0.025 0.05 % of fsr 4 offset 0.012 0.025 % of fsr bipolar zero 0.012 % of fsr integral linearity error 5 1/8 1/2 lsb differential linearity error 1/4 1/2 lsb temperature performance gain drift 5 ppm fsr/c offset drift 5 ppm fsr/c integrated linearity error 5 t min to t max 1/4 1/2 lsb differential linearity error monotonicity guaranteed over full temperature range reference inputs input resistance 5 25 k? voltage range ?11 +11 v dynamic performace setting time (to 1/2 lsb) v prefin = 10 v, change all digital inputs from 5.0 v to 0 v 10 15 s v refin = 0 v to 5 v step, all digital inputs = 0 v 10 15 s reference feedthrough error see figure 2 digital-to-analog glitch impulse 6 250 nv-s crosstalk digital input (static) 7 0.1 lsb reference 8 2.0 mv p-p power requirements supply voltage 9 13.5 16.5 v current (all digital inputs 0 v or 5 v) +v s 40 48 ma ?v s 18 28 ma power dissipation 570 750 mw
ad394 rev. a | page 4 of 12 ad394td and ad394td/883b 1 model min typ max units power supply gain sensitivity +v s 0.002 %fs/% ?v s 0.0025 %fs/% temperature range operating (full specifications) t ?55 125 c storage ?65 150 c 1 the ad394 t grade is available to mil-std- 883, method 5008, class b. see analog devi ces military catalog ( 1985) for proper par t number and detail specification. 2 timing specifications appear in table 5 and figure 6. 3 see the theory of operation section for code tables and graphs. 4 fsr means full-scale range and is equal to 20 v for a 10 v bipolar range and 10 v for a 0 v to 10 v unipolar range. 5 integral nonlinearity is a measure of th e maximum deviation from a straight line pass ing through the endpoints of the dac tran sfer function. 6 this is a measure of the amount of charge injected from the digital inputs to the analog outputs when the inputs change state. it is usually specified as the area of the glitch in nvs and is measured with v refin = agnd. 7 digital crosstalk is defined as the change in any one outputs steady state value as a result of any other output being driven from v outmin to v outmax into a 2k? load by means of varying the digital input code. 8 reference crosstalk is defined as the ch ange in any one output as a result of any other output being driven from v outmin to v outmax @10 khz into a 2 k? load by means of varying the amplitude of the reference signal. 9 the ad394 can be used with supply voltag es as low as 11. 4 v. see . figure 10
ad394 r e v. a | pa ge 5 o f 1 2 absolute maximum ratings table 2. p a r a m e t e r r a t i n g +v s to dgnd ?0.3 v to +17 v ?v s to dgnd ?17 v to +0.3 v digital inputs (p ins 1-16) to dng d ?0.3 v to +7 v v ref i n to dgnd 25 v agnd to dg nd 0.6 v analog output (pins 18, 21, 24, 2 7 ) indefinite short to agnd or dgnd momentary short to v s s t r e s s es a b o v e t h os e lis t e d u n de r a bs ol ut e m a xim u m r a t i n g s ma y c a us e p e r m a n en t dama ge t o t h e de vice . this is a s t r e s s ra t i n g on ly a nd f u n c t i o n a l op era t io n a t o r ab o v e t h is sp e c if ica - t i on i s not i m pl i e d. e x p o su re to ab ove m a x i m u m r a t i ng co ndi t i on s fo r ex ten d e d p e r i o d s ma y a f fe c t de vi ce r e liab 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. f i gure 2. f e edthro ugh v ref i n = 6 0 h z ( t op p h oto) and 4 0 0 h z (b ot to m p h ot o). the s i n e - w ave d i gi tal code is s e t at 1 0 0 0 00 0 00 00 . s c a l e: r e fe r e nce input i s 5 v / d i v ( t hin t r ace ) . f eedt h r o ug h o u t p ut is 5 mv /div . ti me: 5 ms / d iv ( t op p h ot o), 5 0 0 s /div (bot to m p h ot o). mil-std-883 the r i g o rs o f t h e mili t a r y a n d aer o s p ace en vir o nm e n t, tem p - era t ur e ext r e m e s , h u midi ty , m e cha n ical s t r e s s , etc., deman d t h e u t m o s t in e l ec tr o n ic cir c ui ts. the ad394, wi t h t h e in h e r e n t rel i a b i l it y of an i n t e g r a t e d c i rc u i t c o n s t r u c t i on , w a s d e s i g n e d wi t h t h es e a p plica t ion s i n mi nd . the h e r m et i c al l y -s e a le d , lo w prof i l e di p p a ck age t a ke s up a f r a c t i on of t h e s p a c e re qu i r e d by e q ui vale n t m o d u la r desig n s and p r o t e c ts t h e chi p s f r o m h a z a rd ou s e n v i r o n m e n t s . t o f u r t he r i n su re rel i a b i l it y , t h e ad394 is f u l l y co m p lia n t t o mil - s t d-833 class b , m e th o d 5008.
ad394 r e v. a | pa ge 6 o f 1 2 pin conf iguration and fu nctional block di agram f i gure 3. pin config ur ation f i g u re 4. f u nc t i on a l b l o c k d i ag r a m (bi p ol ar)
ad394 r e v. a | pa ge 7 o f 1 2 theory of operation the ad394 q u ad d a c p r o v ides f o ur -q uadran t m u l t i p lica t i o n . i t is a h y b r id i c co m p r i s e d o f fo ur , m o n o li t h ic, 12-b i t, cmos, m u l t i p ly in g d a cs an d ei g h t p r e c isio n o u t p u t am plif iers. e a ch o f t h e fo ur in de p e nden t - b uf fer e d cha n nels has a n i n de p e n d e n t r e fer e n c e i n p u t ca p a b l e o f acc e p t in g a s e p a ra te dc o r ac sig n a l f o r m u lt iply i n g or f o r f u nc t i on ge ne r a t i on a p pl i c a t i o ns . t h e cmos d a cs ac t as dig i t a l l y p r og ra mma b l e a t ten u a t o r s w h e n us e d wi t h a va r y in g i n p u t sig n a l o r , if us e d wi t h a f i xe d dc r e fer e n c e, t h e d a c w o u l d ac t a s a st anda rd b i p o la r o u t p ut d a c. i n ad di t i on, e a ch d a c h a s a 12 -b i t wide d a t a l a t c h t o b u f f er t h e co n v er t e r w h en co nnec t e d t o a micr o p r o ces s o r da ta b u s. multiplying mode f i gur e 5 s h o w s th e tra n sf e r fun c ti o n . th e dia g ra m in d i ca t e s a n a r e a o v er w h ich ma n y dif f er en t co m b ina t io ns of t h e r e fer e n c e in p u t an d dig i t a l in p u t can r e su lt in a p a r t ic u l a r a n a l og o u t p u t v o l t a g e . th e hig h lig h te d t r an sfer lin e i n t h e di ag ra m i n di ca t e s t h e t r a n sfer f u nc t i o n if a f i xe d refer e n c e is a t t h e in p u t. th e dig i t a l co de ab ove t h e d i a g r a m i n d i c a tes t h e mi d p o i n t and e n d p oi n t s of e a ch f u nc t i o n . t h e rel a t i ons h ip b e t w e e n t h e re f e re nc e i n put ( v refin ), th e d i g i tal i n p u t code , a n d th e a n alog o u t p ut is g i v e n i n t a b l e 4. n o t e t h a t t h e r e fer e nce in pu t sig n al se t s t h e s l o p e o f th e tra n sf e r fun c ti o n (a n d de t e rm in e s th e full- s c ale o u t p u t a t c o de 111...111), while t h e dig i t a l in p u t s e lec t s t h e h o r i zo n t al p o si t i o n in eac h dia g ra m. f i g u re 5. th e a d 39 4 as a f o ur - q uadr a n t m u lt ip li er of reference and d i gital input data and contr o l signal format the ad394 acc e p t s 12-b i t p a ral l e l da ta in r e s p o n s e t o c o n t r o l sig n a l s cs1 C cs4 . a s det a i l e d in t a b l e 3, t h e fo ur chi p s e le c t lin e s a r e us e d t o addr es s t h e d a c r e g i s t er o f in ter e s t . i t is p e r - mis s ib le t o ha ve m o r e than on e c h i p s e lec t ac ti ve a t an y time . i f cs1 C cs4 a r e al l b r o u g h t lo w co in ciden t , al l f o ur d a c o u t p u t s w i l l b e up da te d to t h e v a lu e l o c a te d on t h e d a t a b u s . a l l c o n t rol in p u ts a r e le ve l- t r ig ger e d an d m a y b e h a r d - w ir e d lo w t o r e n d er a n y r e gi s t e r (o r gr o u p o f r e gi s t e r s ) tra n s p a r e n t . table 3. dac s e lect matrix cs1 cs2 cs3 cs4 operation 1 1 1 1 a l l dacs latche d 0 1 1 1 load dac 1 fro m data bus 1 0 1 1 load dac 2 fro m data bus 1 1 0 1 load dac 3 fro m data bus 1 1 1 0 load dac 4 fro m data bus 0 0 0 0 a l l dacs simult aneously l o ad e d table 4. bipola r code tabl e data input analo g outpu t analo g outpu t vo ltage, v re f i n = 10 v 1111 1111 1111 1 (v ref i n ) ? ? ? ? ? ? 2048 2047 9.9951 v full scale ? 1 l s b 1100 0000 0000 1 (v ref i n ) ? ? ? ? ? ? 2048 1024 5 . 0 0 0 v 1 / 2 sc a l e 1000 0000 0001 1 (v ref i n ) ? ? ? ? ? ? 2048 1 4.88 mv 1 lsb 1000 0000 0000 1 (v ref i n ) ? ? ? ? ? ? 2048 0 0.000 v zero 0 1 1 1 1 1 1 1 1 1 1 1 ? 1 (v ref i n ) ? ? ? ? ? ? 2048 1 ? 4 . 8 8 m v ? 1 l s b 0 1 0 0 0 0 0 0 0 0 0 0 ? 1 (v ref i n ) ? ? ? ? ? ? 2048 1024 ?5.000 v ?1/2 scal e 0 0 0 0 0 0 0 0 0 0 0 0 ? 1 (v ref i n ) ? ? ? ? ? ? 2048 2048 ?10.000 v ?full sca l e
ad394 r e v. a | pa ge 8 o f 1 2 timi ng the ad394 co n t r o l sig n al timing is v e r y s t ra ig h t f o r w a r d . cs1 C cs4 m u s t ma in t a in a minim u m p u ls e wid t h o f a t le as t 400 n s fo r a desir e d o p er a t io n to o c c u r . w h e n lo adin g d a t a f r o m a b u s in t o a 12 -b i t wide da t a l a t c h, the da t a m u s t be sta b le f o r a t least 210 n s bef o r e r e t u r n in g cs t o a hig h sta t e . w h en cs is lo w , th e da ta la t c h i s tra n s p a r e n t , allo w i n g th e da t a a t th e i n p u t t o p r o p a- ga t e th r o ugh t o th e d a c . da ta ca n c h a n g e imm e d i a t e l y a f t e r th e c h i p s e lec t r e t u r n s hig h . d a c s e t t lin g t i m e is meas ur ed f r o m th e fallin g ed ge o f th e a c ti v e ch i p se lect . table 5. ad39 4 timing speci f ications, t min to t max s y m b o l p a r a m e t e r t y p u n i t s t cs chip select pulse width 170 ns min t da data access tim e 0 ns min t ds data setup tim e 150 ns min t dh data hold time 5 ns min f i g u re 6. ti ming d i ag r a m analog c i rcuit deta ils grounding rules the ad394 in c l udes tw o g r o u nd co nn ec tion s to minimize sy st em acc u rac y deg r ad a t ion ar isin g f r o m g r o u n d in g er r o rs. the tw o g r o u n d p i n s a r e desig n a t e d d g nd (p in 17) a nd a g nd (p i n 23) . th e d g nd p i n is t h e r e t u r n fo r t h e s u p p l y c u r r en t a nd s e r v es as t h e r e fer e n c e p o i n t fo r t h e dig i t a l i n p u t t h r e s h o l d s . t h u s , d g n d s h o u l d b e c o n n e c t e d t o t h e s a m e gr o u n d a s t h e cir c ui tr y th a t d r i v e s th e d i gi t a l i n p u t s . p i n 23, a g n d , i s a h i g h q u ali t y a n alog gr o u n d co n n ect i o n . t h i s pi n s h ou l d s e r v e a s t h e re f e re nc e p o i n t f o r a l l an a l o g cir c ui tr y as s o cia t e d wi t h the ad394. i t is r e co mmende d tha t an y an a l o g s i g n a l p a t h c a r r y i ng s i g n i f i c an t c u r r e n t s h a ve i t s o w n r e t u r n con n e c t i on to pi n 2 3 , as sh own i n f i gur e 7. s e v e ra l com p lic a t i o n s a r is e in prac t i ca l sy st e m s, p a r t ic u l a r ly if t h e lo ad is r e fer r e d t o a r e m o t e g r o u n d . th es e c o m p lic a t i o n s in cl ude dc ga i n er r o rs d u e t o wi r i n g r e sis t a n c e b e tw e e n d a c a nd lo ad , n o i s e d u e t o c u r r en ts f r o m o t h e r cir c ui ts f l o w in g i n p o we r g r ou nd re tu r n i m p e d a nc e s , an d of f s e t s du e to m u lt i p l e lo ad c u r r en ts s h a r in g t h e s a m e s i g n al g r o u n d r e t u r n s. w h i l e t h e d a c o u t p u t s a r e acc u r a tely de velo p e d b e twe e n t h e o u t p ut p i n and pi n 23 (a gnd), del i ver i n g t h e s e sig n a l s to r e m o te lo ads ca n be a p r ob lem. th es e p r ob lem s a r e com p o u n d e d if a c u r r en t b o os t e r s t a g e is us e d , o r if m u l t i p le p a cka g es a r e us e d . f i gur e 8 ill u s t ra t e s th e pa ra si ti c i m p e da n c e s th a t i n f l ue n c e output a c c u r a c y . f i gure 7. r eco mm e n ded g r ound co nn ec tio n s f i g u re 8. g r ou ndin g e r r o rs in m u lt ipl e a d 39 4 sy s t e m s an o u t p u t b u f f er co nf igur e d as a sub t rac t er , as sh o w n i n f i g u re 9 , c a n g r e a t l y re d u c e t h e s e e r ror s . f i r s t , s e ns i n g t h e v o l t a g e dir e c t l y a t t h e lo ad wi t h r4 e l imina t es t h e ef fe c t s o f v o l t a g e dr o p s in wir i n g r e sis t ance . s e cond , s e n s in g the r e m o t e g r o u n d dir e c t l y wi t h r3 e l imina t es t h e v o l t a g e dr o p s ca us e d b y cu rr e n t s f l o w i n g th r o u g h z ga . resis t o r s r1 t h ro ug h r4 sh o u ld b e wel l ma tch e d to achie v e max i m u m r e j e c t io n o f t h e vol t a g e ap p e a r i n g a c r o s s z ga . resis t o r s ma t c h e d t o wi t h in 1 p e r c e n t ( i nclu d i ng t h e e f fe c t s of r w 2 a n d r w 3 ) re d u c e g r ou nd i n t e r a c - tio n er r o rs b y a fac t o r o f 100.
ad394 r e v. a | pa ge 9 o f 1 2 f i gure 9. use of su btr a c t er a m pl if ie r t o pr es er ve ac c u r a c y operat ion from 12 v supplies the ad394 ma y be us ed wi th 12 v 5% p o w e r s u p p lies if ce r t a i n co n d i t i o n s a r e m e t . th e m o s t im po r t a n t li m i t a ti o n i s th e output s w i n g a v ai l a bl e f r om t h e output op am p s . t h e s e am pl i - f i ers a r e ca p a b l e o f swin g i n g o n ly u p t o 3 v f r o m ei t h er s u p p l y . t h u s , t h e nor m a l 1 0 v output r a nge c a n n o t b e u s e d . c h ang i n g t h e o u t p ut s c ale is acco m p lish e d b y cha n g i n g t h e r e fer e nce v o l t a g e . w i t h a s u p p l y o f 11.4 v (5% les s than 12 v), th e o u t p ut ra n g e is r e st r i c t e d to a max i m u m 8.4 v sw ing. i t ma y be us ef u l t o s c ale th e o u t p u t a t 8.192 v (yie ldin g a s c ale fac t o r of 4 m v p e r l s b ) . f i gur e 10 s h o w s a s u g g es t e d circ ui t t o s e t u p a 8.192 v o u t p u t ra n g e . t o h e l p p r ev en t p o o r ga in dr if t d u e t o a p o s s i b le mis- ma tch b e twe e n r in an d r th e v e n i n o f t h e divi der n e tw o r k, i t is r e co mme n d e d to b u f f er r in , t h e p o te n t i o me te r w i p e r volt ag e, wi t h an o p -07. f i gure 10. con n ec ti ons fo r 8 . 1 9 2 v f u ll s c al e (r ec o m m e nded f o r 1 2 v p o wer s u p p l i es) power supply decoupling the p o w e r s u p p lies us ed wi t h th e ad394 sh o u l d b e w e l l - f i l t er e d an d re g u l a te d. l o c a l supply d e c o upl i ng c o ns i s t i ng of a 1 0 f ta n t al u m c a pa ci t o r i n pa r a ll e l wi th 0.1 f ceramic ca p a c i t o r is s u g g es t e d . th e deco u p lin g ca p a ci t o rs sh o u ld b e co nn ec t e d bet w een t h e s u p p l y p i n s a n d t h e a g n d p i n . i f a n o u t p u t bo os t e r is us e d , i t s s u p p lies sh ou ld als o be de cou p le d t o t h e l o a d g r ou nd. impro v ing full-scale stability i n la rg e syst em s usin g m u l t i p le d a cs, i t ma y be desira b l e fo r al l d e v i c e s to sh are a c o m m o n re f e re nc e. a pre c i s i o n re f e re nc e c a n g r e a t l y im p r o v e sys t em acc u rac y a n d t e m p era t ur e s t a b i l i t y . the ad2710 is a s u i t a b le r e f e r e n c e s o ur ce f o r s u c h sys t em s. i t fe a t ur es a gu a r an t e e d maxi m u m t e m p er a t ur e co ef f i cien t o f 1 p p m /c. th e co m b ina t ion o f th e ad2710l n a nd ad394, as shown i n f i g u re 1 1 , y i el ds a m u lt i p l e d a c s y ste m wi t h max i - m u m f u l l -s ca le dr if t o f 6 p p m /c and excel l en t t r ack i n g . f i g u re 11. l o w d r if t conf ig u r at ion applic ati o ns interfacing the ad394 to micropro cessors the ad394 co n t r o l log i c p r o v ides a sim p le in t e r f ace t o micr o- p r o c ess o rs. t h e indivi d u a l l a t c hes a l lo w fo r m u l t i-d a c in t e r - f a c i ng to a s i ng l e d a t a b u s . 16-bit process o rs the ad394 is a 12-b i t r e s o l u tion d a c sys t em and is easil y in ter f ace d to 16 -b i t wide d a t a b u s e s. s e ver a l p o ssi b le a ddr essing co nf igura t io n s e x ist. i n t h e cir c ui t sho w n in f i gur e 1 2 , a sys t em wr i t e sig n al is us e d t o co n t r o l th e deco de d addr ess lin e s and a 74l s 139 deco der dr i v en f r o m t h e le as t sig n if ic a n t addr es s b i ts p r o v ides t h e ac t i ve-lo w cs1 th r o ugh cs4 sig n als. i n th e cir c ui t in f i gur e 12, addr ess li n e s a0 a nd a1 e a ch s e l e c t a sin g le d a c o f t h e fo ur co n t a i ned in t h e ad394. the us e o f a s e p a ra t e addr es s lin e f o r e a ch d a c a l l o ws s e ve r a l d a c s to b e ac c e ss e d s i m u l t ane o u sly . the addr es s li nes a r e ga t e d b y t h e si m u l t ane o us o c c u r r en ce o f a sys t em wr a nd t h e a p p r o p r i a t ely de co de d b a s e ad dr ess. i n t h e addr es sing s c h e me sh o w n in f i gur e 12, a0 r e p r es en ts t h e le ast sig n if ic a n t w o r d addr ess b i t. d a t a ma y r e side in e i t h er t h e 12 ms bs (lef t-j u s t if ied) o r th e 12 ls bs (r ig h t -j us tif i ed). l e f t j u st if ic a t ion is us ef u l w h en t h e d a t a -w o r d r e p r e s en ts a b i na r y f r a c ti o n o f full scale , wh ile ri g h t- j u s t i f i e d da ta us uall y r e p r e s e n ts a n in t e ger val u e betw een 0 an d 4095. f i g u re 12. 1 6 -bit bu s inter f ac e
ad394 rev. a | page 10 of 12 8-bit processo rs the cir c ui t o f f i gur e 13 s h o w s t h e g e n e ral p r i n c i ples fo r co nnec t in g t h e ad394 t o an 8-b i t da t a b u s. the 74ls244 b u f f ers t h e da t a b u s; i t s o u t p uts a r e enab le d w h en t h e d a c addr es s a p p e a r s o n t h e addr es s b u s. the f i rs t b y t e s e n t t o t h e d a c is lo aded t o the 74 ls373 o c tal l a t c h an d , when t h e s e co nd b y te is s e n t to t h e d a c , i t i s c o m b i n e d w i t h t h e f i rst b y te to c r e a t e a 12-b i t w o r d . t h e co n n e c t i o n s sh o w n a r e fo r r i g h t-hand j u st if ie d da ta . cs a nd wr i n p u ts t o th e d a c a r e also ga t e d , a n d w h en a c ti v e , th e d a c i s loa d ed . pull- u p r e si s t o r s a t th e o u t p u t o f th e 74ls244 b u f f er en s u r e tha t the in p u ts t o th e d a c do n o t f l o a t a t a n i l l- def i n e d l e vel w h e n t h e d a c is n o t b e in g addr ess e d . this m e t h o d o f co nnec tin g 12-b i t d a cs t o a n 8-b i t da ta b u s is m o s t cos t ef f e c t i v e w h en m u l t i p le d a cs a r e u t ilize d f o r 8-b i t da ta b u s ap p l i c at i o n s . f i g u re 13. 8-b i t d a t a bus in ter f ac e applic ati o ns the f u n c tio n al den s i t y o f th e ad394 p e r m i t s c o m p lex a n alog f u n c t i o n s to b e p r o d uce d u nder dig i t a l co n t r o l, w h er e b o a r d sp ace r e q u ir e m en ts w o u l d o t h e r w is e b e p r ohib i t i v e . m u l t i p le - output pl otte r s , m u lt i c h a n n el d i spl a y s , c o m p l e x w a ve f o r m gen e r a t i o n , and m u l t i p le p r o g r a mma b l e vol t a g e s o ur ces ca n a l l b e i m ple m e n t e d wi t h t h e ad39 4 in a f r ac t i o n of t h e sp ace t h a t w o u l d be neede d if s e p a ra te d a cs w e r e us ed . using the ad3 94 for analog-to-digital conv ersion m a n y sys t em s req u ir e b o th a n a l og o u t p u t and a n alog in p u t ca p a b i li ty . w h i l e co m p lete in t e g r a t e d c i r c ui t ana l og-t o-dig i t a l co n v er t e rs (s uch as t h e ad574 a) a r e r e adi l y a v a i lab l e , t h e ad394 can be u s ed as t h e p r ecisio n a n alog s e c t io n o f a n ad c if s o m e ext e r n al log i c is a v a i la b l e . s e v e ral typ e s o f a n alog-t o- dig i t a l con v er te rs ca n b e b u i l t wi t h a d a c, com p a r a t o r , an d co n t r o l log i c, inc l udin g sta i r c as e , trac kin g , and s u cces si v e - ap p r ox i m at i o n t y p e s . in s y s t e m s t h at i n c l u d e a m i c r o p r o - c e s s o r , o n l y a co m p a r a t o r m u s t b e adde d t o the ad394 t o acco m p lish t h e ad c f u n c t i o n si n c e t h e p r o c es s o r can p e r f o r m t h e r e q u ir e d d i g i t a l op e r a t i o ns u n d e r s o f t w a re c o n t ro l. a su it abl e c i rc u i t i s s h own in f i gur e 14. th e ad311 co m p a r a t o r co m p a r es th e unkn own in p u t v o l t a g e t o on e of th e ad394 o u t p u t s f o r th e a n alog-t o-dig i t a l co n v ersio n , w h i l e t h e o t h e r t h r e e o u t p uts a r e us e d as n o r m al d a cs. th e dio d e clam p sh o w n limi t s t h e v o l t a g e s w i n g a t t h e com p a r a t o r in p u t an d i m p r o v es co n v ersio n sp e e d . w i t h ca ref u l la yo u t , a ne w co m p a r -is o n ca n b e p e r f or me d i n l e ss t h an 1 5 s , re su l t ing i n a 1 2 - b it su c c e s s i ve a p p r o x ima t ion co n v ersio n in u n der 180 s. the ben e f i t o f usin g th e ad394 in this a p p l ic a t ion is tha t on e ad c and thr e e d a cs ca n be im p l em en t e d wi t h o n l y tw o i c p a c k a g es (th e ad394 and th e co m p a r a t o r ). f i gure 1 4 . usi n g o n e ad394 o u tput fo r a/d co n v ers i o n programmabl e wind ow c o mp ar ator the ad394 can be us e d t o p e r f o r m limi t t e s t ing o f r e s p o n s e s to d i gi tall y c o n t r o ll ed i n p u t s i gn als . f o r e x a m p l e , t w o d a c s ma y b e u s e d to ge ne r a te s o f t w a re - c on t r ol l e d te st c o nd i t i o ns for a co m p on e n t o r c i r c ui t. th e r e sp o n s e t o t h es e i n p u t con d i t io n s c a n b e e i t h e r c o m p l e tely c o n v e r te d f r om an a l o g to di g i t a l or sim p ly t e st e d a g a i n s t hig h an d l o w limi ts ge n e r a t e d b y t h e tw o d a cs in the ad394. f i g u re 15. p r og r a m m ab le w i ndow co mpa r a t or u s ed in p o we r - sup p ly t e s t ing i n t h e cir c ui t sho w n in f i gur e 1 5 , tw o ad311 vol t a g e com p a r - a t o r s a r e us e d w i t h i n t h e a d 394 t o t e s t t h e o u t p u t o f a 5 v p o w e r - s u p p l y r e gu la t o r . th e ad394 v ou t 1 output ( t h r ou g h an a p p r o p r i a t e c u r r en t b o os t e r) dr i v es t h e in p u t t o t h e r e gu l a t o r t o s i m u l a te v a r i a t i o ns i n i n put volt age. t h e output of t h e re g u l a tor is a p plie d to c o m p a r a t o r s 1 and 2, w i t h t h eir ou t p uts wir e -
ad394 rev. a | page 11 of 12 or e d wi t h led indic a to rs as sho w n. t h e test li mi ts fo r e a ch co m p a r a t o r a r e p r og ra mm e d b y th e ad394 v ou t 2 and v ou t 3 output s . whe n t h e output of t h e d e v i c e u n d e r te st i n g i s w i t h i n t h e l i m i t s , b o t h c o m p ar a t ors are of f and d 1 l i g h t s . i f t h e out p ut is a b o v e o r b e lo w t h e limi ts, ei t h er d4 o r d5 li g h ts. ad394 as a multiplier and a ttenuator s o fa r , i t has b e e n ass u me d t h a t t h e r e fer e n c e v o l t a g e v refin is fi x e d . i n f a c t , v re f i n ca n b e an y vol t a g e wi t h in t h e ra n g e o f ?11 v < v refin < + 1 1 v . i t c a n b e ne g a t i ve, p o s i t i ve, s i n u s o i d a l , or w h a t e v er t h e us er p r efers. this l e ads t o t h e name m u l t i pl yin g d/a con v er t e rs b e c a us e t h e o u t p u t v o l t a g e , v ou t , i s prop or - ti o n al t o th e p r o d uct o f th e d i gi t a l i n p u t w o r d a n d th e v o l t a g e a t th e v refin te r m i n a l . () () () 4095 d 0 4096 d v 1 v refin out < < ? = d i s th e f r a c ti o n al b i n a r y v a l u e o f th e d i g i tal w o r d a p p l i e d t o t h e co n v er t e r . th e ad394 m u l t i p lies th e dig i t a l in p u t val u e b y t h e an a l o g i n put volt age a t v refin fo r an y va l u e o f v refin up to 22 v p-p . this i n i t s e lf is a p o wer f u l t o ol. a p plica t ion s r e q u ir ing p r e c isio n m u l t i p lica t i on wi t h minim a l zer o o f fs et a nd ver y lo w dis t o r tio n sh o u l d co n s ider t h e ad394 as a candida te . o n e p o p - u l a r us e f o r th e ad394 is as an a u dio f r eq uen c y a t t e n u a t o r . the a u dio sig n a l is a p plie d t o t h e v re f i n in p u t an d t h e a t t e n u a t io n co de is a p plie d to t h e d a c; t h e o u t p ut v o l t a g e is t h e p r o d uc t o f t h e tw oa n a t ten u a t e d v e rsio n o f t h e in p u t. the maxim u m a t t e n u a t io n rang e ob taina b le u t ilizin g 12 b i ts is 4096:1 o r 72 db . f i g u re 16. a d 3 9 4 a s a m u lt ipl i e r o r at t e nuat or
ad394 rev. a | page 12 of 12 package outline 0.023 (0.58) 0.014 (0.36) 0.180 (4.57) min 0.620 (15.75) 0.550 (13.97) 1 14 15 28 1.575 (40.01) max 0.225 (5.72) max 0.145 (3.68) min 0.035 (0.89) 0.015 (0.38) 0.015 (0.38) 0.008 (0.20) 0.810 (20.57) 0.770 (19.56) 0.100 (2.54) bsc 0.070 (1.78) 0.030 (0.76) 0.137 (3.48) max pin 1 see note 1 see note 2 see note 6 see note 4, 7 see note 3 see note 5 notes 1. index area; a notch or a lead one identification mark is located adjacent to lead one. 2. the minimum limit for dimension may be 0.023" (0.58 mm) for all four corner leads only. 3. dimension shall be measured from the seating plane to the base plane. 4. the basic pin spacing is 0.100" (2.54 mm) between centerlines. 5. applies to all four corners. 6. measured at the centerline of the leads. 7. twenty six spaces. 8. controlling dimensions are in inches. millimeter dimensions are rounded-off millimeter equivalents for reference only and are not appropriate for use in design f i gure 17. 28-l ead bott om-b r a z e d c e r a mic dip for hybr id [bbdip/h] (dh-28a) d i m e ns i o ns sh o w n in i n ches and ( m il li met e rs ) n o te: s q ua r e d c o r n er a nd d o t in shade d ar e a i ndic a te pin 1. ordering guide model temperature r a nge gain error linearity error (t min Ct ma x ) ad394td ?55c to +125c 2 lsb 1/2 lsb ad394td/883b ?55c to +125c 2 lsb 1/2 lsb ? 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 . c04851-0-9/04(a)

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