pt1101 pwm/vfm s t ep-down dc-dc contr o ller ? general description t he pt 1 101 series are cm os-based pw m step-do w n dc/dc contro llers w i th lo w supp l y curr ent. a lo w rip p le, hig h ef ficie n c y ste p - d o w n d c /dc c onverter ca n b e easil y com p o s ed of w i t h ad ditio nal sev e ral extern al comp one nt s such as a po w e r-transist o r , an inductor , a diode a nd cap a cit o rs. output vo lt age is fixed or can be adjuste d w i t h ext e rna l resister s . (pw m /vf m alternativ e circuit is disa ble d in a d just a b le t y pes ) t he pt 1 101 series co nsist o f a pw m control circu i t, a hig h pr ecis ion ba nd-g ap vo lt age reference, a s o f t -st a rt circuit, a protectio n circ uit, a pw m/vfm altern ative c i rcuit, an oscil l a tor , an error a m plifier w i th i n terna l comp ens ation net w o rk an d inp u t/output vol t age detecti on circuit s . w i th it s interna l st ate-of-art control alg o rithm, the pt 1 101 series bas ed d c /dc converte r can achiev e hig h performa n c e w h il e ma int a i n i ng st ab ilit y . for examp l e, w i t h it s pwm/vfm alte rn ative circ uit, w h e n the lo ad curr ent is s m all, the op era t ion is automatica l l y s w i t che d into the vf m m ode to improve the ef ficie n c y . f u rther , if the term of maximum du t y c y cl e keep s o n a cert ain time, the embedd e d protection cir c uit s rest art t he operati on w i t h sof t -st a rt and repeat until the maximum d u t y c y cl e con d iti on is rele ase d . fin a ll y , bu ilt-in uv lo function blo cks potenti a ll y unst a b l e o u tput w h en t he i nput volt age is eq u a l or less than u v lo threshol d and mak e s this ic st andb y for lo w p o w e r co n s umptio n. ? fea t ures ? w i de ra nge o f input v o lt age: 2.3v ~ 18 v ? built-in s o f t -st a rt and protectio n f unction ? high ef fici enc y: t y p. 9 0 % ? oscillatio n fre que nc y : 50 0k hz ? high accur a c y output v o lt age : 2% ? lo w t e mper atu r e coef fici ent o f output v o lt age: t y p . 1 00 pp m/ ? s t andb y c u rre nt: t y p. 0.1 a ? output v o lt age : s t ep w i se s e tting w i t h a s t ep of 0.1v in the ran ge of 1.2v to 6.0v as fixed volt ag e t y p e . referenc e v o lt age of adjust abl e t y pe is 1.0v . ? cmos output cap a bilit y ? small pack age : sot - 23-5 ? applica t ions po w e r sources for: ? han d -he l d co mmunicati on equ ipme nt, cameras, video instrument s such as vcrs, camcorder s ? batter y - p o w e r e d equ ipme nt ? hous eho ld e l e c trical ap pli anc es ? orderin g informa t ion pack a g e t e m p eratu r e ran g e o r d e rin g part numbe r tr a n s p o r t m a r k i n g pt 1 101e23e- 1 0 (adjust a ble output v o lt age ) t ape and r eel 1 1 0 1 pt 1 101e23e- 3 3 (3.3v output v o lt age) t ape and r eel 1 1 0 1 c sot - 23-5, pb-free -40 to 125 pt 1 101e23e- 5 0 (5.03v outpu t v o lt age) t ape and r eel 1 1 0 1 d datasheet rev 1. 0, china resour ces powtech ( s hanghai) l i m ited p a g e 1
pt1101 pwm/vfm step-down dc-dc controller ? typical application circuit ? fixed output voltage type pmos: irf7406 (ir) l: cr105-270mc (sumida, 27h) sd1: rb063l-30(rohm) c3: 47f, tantalum type c1: 10f, ceramic type c2: 0.1f, ceramic type r1: 10 ? ? adjustable output voltage type. fo r example, output voltage=3.2v pmos: irf7406 (ir) l: cr105-270mc (s umida, 27h) sd1: rb063l-30(rohm) c3: 47f, tantalum type c1: 10f, ceramic type c2: 0.1f, ceramic type c4: 1000pf, ceramic type r1: 10 ? r2: 10k ? r3: 2.7 k? r4: 22 k ? datasheet rev 1.0, china resources powtech (shanghai) limited page 2 o?^?uf?m?w3^v?mw`r?y?b?g ?pqls? tel: 0755-8398 3377 / 135 9011 2223 http://www.gofotech.com
pt1101 pwm/vfm step-down dc-dc controller ? pin assignment ? pin descriptions pin no. names description 1 ce chip enable. active with ?h? 2 gnd ground 3 v out / (v fb ) output voltage (feedback voltage for adjustable output voltage type) 4 ext external transistor driver pin (cmos output) 5 v in power supply ? absolute maximum ratings sym parameter value v in v in supply voltage 20v v ext ext pin output voltage -0.3~vin +0.3v v ce ce pin input voltage -0.3~vin +0.3v v out / (v fb ) v out / (v fb ) pin input voltage -0.3~6v i ext ext pin output current 50ma pd power dissipation 250mw t opt operation temperature range -40~85 t stg storage temperature range -55~125 ? operating range sym parameter value v in v in supply voltage 2.5~18v v ext ext pin output voltage -0.3~vin +0.3v v ce ce pin input voltage -0.3~vin +0.3v v out / (v fb ) v out / (v fb ) pin input voltage -0.3~5.5v i ext ext pin output current 50ma datasheet rev 1.0, china resources powtech (shanghai) limited page 3 o?^?uf?m?w3^v?mw`r?y?b?g ?pqls? tel: 0755-8398 3377 / 135 9011 2223 http://www.gofotech.com
pt1101 pwm/vfm step-down dc-dc controller ? electrical characteristics ( t opt =25 , unless otherwise noted.) ? adjustable output voltage type symbol parameter conditions min. typ. max. units v in operating voltage 2.3 18 v v fb feedback voltage v in =v ce =8v, i fb =350ma 0.98 1.00 1.02 v t v fb ? ? feedback voltage temperature coefficient -40 7 2 3 7 100 ppm/ i q1 supply current v in = v ce =18v, v fb =2v 40 80 -a i q2 shutdown current v in = 18v, v ce =v fb =0v 0.1 1 -a f osc oscillator frequency v in =v ce =8v, i fb =350ma 400 500 600 khz d max maximum duty cycle 100 % d min minimum duty cycle 0 % i exth ext ?h? output current v in =v ce =8v, v ext =7.9v, v fb =3v -17 -10 ma i extl ext ?l? output current v in =v ce =8v, v ext =0.1v, v fb =0v 20 30 ma i ceh ce ?h? output current v in =v ce =v out =18v 0 0.5 ua i cel ce ?l? output current v in = v out =18v, v ce =0v -0.3 0 ua v ceh ce ?h? input voltage 1.5 v v cel ce ?h? input voltage v in =8v, v fb =0v 0.3 v v uvlo1 uvlo voltage v in =v ce =2.5v->1.5v, v fb =0v 1.75 2.0 2.25 v v uvlo2 uvlo release voltage v in =v ce =1.5v->2.5v, v fb =0v v uvlo1 +0.1 2.4 v t sst delay time by soft-start v in =8v, i fb =10ma , v ce =0v->2.5v 5 10 20 ms t prot delay time by protection v in =v ce =2.5v, v fb =2.5v->0v 5 15 30 ms ? fixed output voltage type symbol parameter conditions min. typ. max. units v in operating voltage 2.3 18 v v fb feedback voltage v in =v ce =v set +1.5v, i out =100ma v set x0.98 v set v set x1.02 v t v fb ? ? t v fb ? ? feedback voltage temperature coefficient -40 1.5v, v out =0v 1.75 2.0 2.25 v v uvlo2 uvlo release voltage v in =v ce =1.5v->2.5v, v out =0v v uvlo1 +0.1 2.4 v t sst delay time by soft-start v in =v set +1.5v, i out =10ma , v ce =0v->v set +1.5v 5 10 20 ms t prot delay time by protection v in =v ce =v set +1.5v, v out =v set +1.5v->0v 5 15 30 ms datasheet rev 1.0, china resources powtech (shanghai) limited page 4 o?^?uf?m?w3^v?mw`r?y?b?g ?pqls? tel: 0755-8398 3377 / 135 9011 2223 http://www.gofotech.com
pt1101 pwm/vfm step-down dc-dc controller ? simplified block diagram ramp pwm vref erramp vref ramp pwm vref erramp vref fixed output voltage type adjustable output voltage type ? operation description the power stage of pwm step-down dc/dc converter can be se en as an input voltage chopping circuit followed by an l-c filter. unlike the linear regulator which operates the power transistor in the linear mode, the pwm switching regulator operates the power transistor either in saturation or cutoff regions. due to the voltage-ampere product of power transistor under these two operation modes keeps low, high efficiency can be easily achieved. the dc input voltage is firstly chopped into square waves whose magnitude is the same as input voltage and whose duty cycle is manipulated by the switching regulator controller, her eby is pt1101. with the use of following appropriately chosen l-c filter, such square wave modulation could be eliminated and ripple free dc voltage equal to the average of the duty cycle modulated dc input voltage results. the regulated output voltage is maintained by the controller, which operates much like a linear style controller. that is, by sensing the dc output and controlling duty cy cle in a negative-feedback loop, the dc output could be regulated against input line and output load changes. the operation of step-down dc/dc converter can be understood by braking its operation into two period. when the switch is turned on, the input voltage is presented to the l-c filter, the inductor current (i1) ra mps linearly upward from ilmin to ilmax and stores energy in itself. when the switch is turned off, the input voltage to inductor flies below ground and the schottky diode becomes forward biased. this continues to conduct current (i2) which is formerly flowing through switch and some of the stored energy is discharged to load. therefore a local current loop including diode, inductor and load comes into being. datasheet rev 1.0, china resources powtech (shanghai) limited page 5 o?^?uf?m?w3^v?mw`r?y?b?g ?pqls? tel: 0755-8398 3377 / 135 9011 2223 http://www.gofotech.com
pt1101 pwm/vfm step-down dc-dc controller ? application information ? to avoid parasitic current into each pin, make sure voltage applied to ce pin should be no more than the voltage level of vin pin. ? the protection circuit may work if the term of maximum duty cycle continues for a certain time. as the result, v out will be reset and settled by soft start operation until the maximum dut y cycle condition is released. be aware that if the differential voltage between vin and vout is qui te small, protection f unction may be trigged. ? use schottky diode for high switching speed applicat ion. pay attention to its current capability. ? do not apply pt1101 to the condition with vi n is equal or less than minimum operation voltage. ? if the ratio of output voltage against input voltage is 35 % or less while heavily loaded, pt1101ax keeps its vfm mode for low frequency operation. theref ore the output ripple voltage may be la rge. the phenomena are the typical characteristics of the pwm/vfm alternative circuit. ? to adjust output voltage when using pt1101b, follow the equation shown below, in which v fb is equal to 1v. 2 42 r rr vv fb out + = thus, with changing the value of r2 and r4, output voltage can be set in the specified range. ? to provide enough phase margin for stable operation, some critical components associated with local compensation network formed by r4 and c4 should be chosen correctly. fo llowing procedure can help to find the suitable value of r and c. firstly, find the double pole caused by l and c3. 32 1 cl f pole ? = next, place a zero formed by r4 and c4 as much as . pole f 442 1 cr f zero ? = finally, choose r3 about one tenth of r4 for noise attenuation on feedback path. for example, if l=27h, c3=47f, the cut off frequency of the pole is approximately 4.5khz. choose r4=33k ? and c4=1000pf to meet with compensation requ irement. if vout is set to 2.5v, r2=22k ? is appropriate. r3 can be set to one tenth of r3, that is, 3 k ?. ? external component selection guide ? inductor select an inductor that peak current does not exceed ilmax. for constant load current, the smaller inductor value, the larger output ripple voltage. ? diode use a diode with low vf (schottky diode is recommended) and high switching frequency. reverse voltage rating should be more than vin and current rating should be larger than ilmax. ? capacitors as for vin, use a 10f capacitor with low esr for stable operation. cout can reduce output ripple volta ge, therefore a 47f or more tantalum type capacitor is recommended. ? power transistor pch power mosfet is required for pt1101. its breakdown voltage between gate and source should be a few higher than vin. datasheet rev 1.0, china resources powtech (shanghai) limited page 6 o?^?uf?m?w3^v?mw`r?y?b?g ?pqls? tel: 0755-8398 3377 / 135 9011 2223 http://www.gofotech.com
pt1101 pwm/vfm step-down dc-dc controller if heavily loaded, choose mosfet with low rds(on) for good efficiency. if lightly loaded, choose mosfet with low gate capacitance for good efficiency. current rating of power mosfet should be larger than ilmax. ? typical performance characteristics note: typical characteristics are obtained with using the following components: pmos: irf7406 (ir) c1: 10f, ceramic type c4: 1000pf, ceramic type r3: 2.7 k? l: cr105-270mc (sumida, 27h) c2: 0.1f, ceramic type r1: 10 ? r4: 22 k ? sd1: ss24 c3: 47f, tantalum type r2: 10k? 1. output voltage vs. output current output voltage vs. output current pt1101b@vout=3.2v 3.18 3.19 3.2 3.21 3.22 0.1 1 10 100 1000 2000 output current (ma) output voltage (v) vin4.8v vin7.5v vin10v vin15v output voltage vs. output current pt1101b@vout=5v 4.98 4.99 5 5.01 5.02 5.03 5.04 5.05 5.06 0.1 1 10 100 1000 2000 output current (ma) output voltage (v) vin6.5v vin9v vin12v vin15v 2. efficiency vs. output current efficiency vs. output current pt1101b@vout=3.2v 0 10 20 30 40 50 60 70 80 90 100 0.1 1 10 100 1000 2000 output current (ma) efficiency (%) vin4.8v vin7.5v vin10v vin15v efficiency vs. output current pt1101b@vout=5v 0 10 20 30 40 50 60 70 80 90 100 0.1 1 10 100 1000 2000 output current (ma) efficiency (%) vin6.5v vin9v vin12v vin15v datasheet rev 1.0, china resources powtech (shanghai) limited page 7 o?^?uf?m?w3^v?mw`r?y?b?g ?pqls? tel: 0755-8398 3377 / 135 9011 2223 http://www.gofotech.com
pt1101 pwm/vfm step-down dc-dc controller 3. ripple voltage vs. output current ripple voltage vs. output current pt1101b@vout=3.2v 0 5 10 15 20 25 30 35 40 45 0.1 1 10 100 1000 2000 output voltage (ma) ripple voltage (mv) vin4.8v vin7.5 vin10v vin15v ripple voltage vs. output voltage pt1101b@vout=5v 0 5 10 15 20 25 30 35 40 0.1 1 10 100 1000 2000 output current (ma) ripple voltage (mv) vin6.5v vin9v vin12v vin15v 4. output voltage vs. input voltage output voltage vs. input voltage pt1101b@vout=3.2v 3.18 3.185 3.19 3.195 3.2 3.205 3.21 3.215 4.8 7.5 10 15 input voltage (v) output voltage (v) 0.1ma 1000ma output voltage vs. input voltage pt1101b@vout=5v 4.99 5 5.01 5.02 5.03 5.04 5.05 6.5 9 12 15 input voltage (v) output voltage (v) 0.1ma 1000ma datasheet rev 1.0, china resources powtech (shanghai) limited page 8 o?^?uf?m?w3^v?mw`r?y?b?g ?pqls? tel: 0755-8398 3377 / 135 9011 2223 http://www.gofotech.com
pt1101 pwm/vfm step-down dc-dc controller 5. load transient response (1) i load =0a ? 1a (2) i load =1a ? 0a datasheet rev 1.0, china resources powtech (shanghai) limited page 9 o?^?uf?m?w3^v?mw`r?y?b?g ?pqls? tel: 0755-8398 3377 / 135 9011 2223 http://www.gofotech.com
pt1101 pwm/vfm step-down dc-dc controller ? package information datasheet rev 1.0, china resources powtech (shanghai) limited page 10 o?^?uf?m?w3^v?mw`r?y?b?g ?pqls? tel: 0755-8398 3377 / 135 9011 2223 http://www.gofotech.com
|
