power management 1 www.semtech.com SC1157 programmable synchronous dc/dc controller for advanced processors features applications revision 4/01 description the SC1157 is a low-cost, full featured, synchronous voltage-mode controller designed for use in single ended power supply applications where efficiency is of primary concern. synchronous operation allows for the elimination of heat sinks in many applications. the SC1157 is ideal for implementing dc/dc converters needed to power advanced microprocessors such as the pentium ? ll , in both single and multiple processor configurations. internal level-shift, high-side drive circuitry, and preset shoot-thru control, allows for use of inexpensive n-channel power switches. SC1157 features include an integrated 4-bit vid dac, temperature compensated voltage reference, triangle wave oscillator, current limit comparator, frequency shift over-current protection, and an internally compensated error amplifier. the SC1157 operates at a fixed 140khz, providing an optimum compromise between efficiency, external component size, and cost. u low cost / full featured u synchronous operation u 4 bit vid dac programmable output (1% tolerance) u designed to meet intel vrm8.2 (pentium ? ii) u 1.5% reference u pentium? ii core supply u multiple microprocessor supplies u voltage regulator modules (vrm) u programmable power supplies u high efficiency dc/dc conversion r19 18.7 r20 100 u1 SC1157cs 1 3 2 5 4 7 10 11 12 13 14 15 16 8 6 9 gnd vcc ref cs+ cs- dh bsth en vosense vid3 vid2 vid1 vid0 dl pgnd bstl q5 si4410 c12 0.01uf + c7 1500uf r5 1.00k c4 0.1uf + c24 330uf r21 97.6 phase q3 si4410 + - u2b lm358 5 6 7 8 4 c13 0.1uf r9 2.2 r7 5mohm r16 1k q6 irlr024n 12v vccp c5 0.1uf r1 10 + c17 1500uf r4 2.2 + c15 1500uf 12v + c3 1500uf + c21 1500uf 2.5v r10 2.2 5v + c10 1500uf l1 2uh c6 0.1uf + c2 1500uf + c27 330uf r22 100 q7 irlr024n c11 0.1uf q1 si4410 5v + c9 1500uf vid0 r14 0 r6 2.32k q2 si4410 r12 see table r15 0 vid2 vid1 r8 2.2 c1 0.1uf 1.5v + - u2a lm358 3 2 1 8 4 q4 si4410 vid3 + c8 1500uf 3.3v r13 see table en r3 2.2 + c25 330uf typical application circuit
2 ? 2000 semtech corp. www.semtech.com power management SC1157 electrical characteristics absolute maximum ratings r e t e m a r a pl o b m y sm u m i x a ms t i n u c c vd n g o tv n i 7 o t 3 . 0 -v d n g o t d n g p 1 v d n g o t t s b 5 1 o t 3 . 0 -v e s a c o t n o i t c n u j e c n a d e p m i l a m r e h t q c j 0 3w / c t n e i b m a o t n o i t c n u j e c n a t s i s e r l a m r e h t q a j 0 3 1w / c e g n a r e r u t a r e p m e t g n i t a r e p ot a 0 7 o t 0c e g n a r e r u t a r e p m e t e g a r o t st g t s 0 5 1 + o t 5 6 -c . c e s 0 1 ) g n i r e d l o s ( e r u t a r e p m e t d a e lt d a e l 0 0 3c ) l e d o m y d o b n a m u h ( g n i t a r d s ed s e5 . 1v k unless specified: vcc = 4.75v to 5.25v; gnd = pgnd = 0v; fb = v o ; 0mv < (cs+ - cs-) < 60mv; t j = 25 o c r e t e m a r a ps n o i t i d n o cn i mp y tx a ms t i n u e g a t l o v t u p t u o . e l b a t d i v e e s e g a t l o v y l p p u sc c v5 . 47v t n e r r u c y l p p u sv 0 . 5 = c c v85 1a m n o i t a l u g e r d a o li o a 5 1 o t a 3 . 0 = ) 1 ( 1% n o i t a l u g e r e n i ls e d o c d i v l l a ) 1 ( 5 1 . 0 % ) l o a ( n i a gp c c v o t e s n e s o v5 3b d e g a t l o v t i m i l t n e r r u c 0 60 70 8v m y c n e u q e r f r o t a l l i c s o 5 2 10 4 15 5 1z h k e g a t l o v e c n e r e f e r d e r e f f u bi f e r a m 15 2 . 1v e l c y c y t u d x a m r o t a l l i c s o 0 95 9% t n e r r u c e c r u o s / k n i s h dv 3 = h d n g p - h d , v 5 . 4 = h d - h t s b1a t n e r r u c e c r u o s / k n i s l dl d n g p = l d , v 5 . 4 = l d - l t s bv 3 =1 a e m i t d a e d 0 50 0 1s n t n e r r u c e c r u o s n i p d i vx d i v v 4 . 20 30 0 1 m a note: (1) specification refers to eval board schematic. (2) this device is esd sensitive. use of standard esd handling precautions is required.
3 ? 2000 semtech corp. www.semtech.com power management SC1157 pin configuration ordering information pin descriptions 1 2 3 4 5 6 7 8 vid0 gnd top view (16 pin soic) 13 12 14 15 16 11 10 9 vid1 ref vid2 vcc vid3 cs- vosense cs+ en pgnd bsth dh bstl dl note: (1) only available in tape and reel packaging. a reel contains 2500 devices. (2) nb indicates 150 mil body. e c i v e d ) 1 ( e g a k c a pt ( e g n a r p m e t j ) r t . s c 7 5 1 1 c sb n 6 1 - o sc 5 2 1 o t 0 # n i pe m a n n i pn o i t c n u f n i p 1d n gd n u o r g l a t i g i d d n a g o l a n a l a n g i s l l a m s 2f e rt u p t u o e c n e r e f e r d e r e f f u b 3c c ve g a t l o v y l p p u s p i h c 4- s c) e v i t a g e n ( t u p n i e s n e s t n e r r u c 5+ s c) e v i t i s o p ( t u p n i e s n e s t n e r r u c 6d n g ps r e v i r d e d i s w o l d n a h g i h r o f d n u o r g r e w o p 7h dt u p t u o r e v i r d e d i s h g i h 8l dt u p t u o r e v i r d e d i s w o l 9l t s b) t s o o b ( r e v i r d e d i s w o l r o f y l p p u s 0 1h t s b) t s o o b ( r e v i r d e d i s h g i h r o f y l p p u s 1 1n e . n o i t a r e p o l a m r o n r o f n e p o r o h g i h , r e t r e v n o c e h t n w o d s t u h s w o l c i g o l , n i p e l b a n e 2 1e s n e s o v. n i a h c k c a b d e e f l a n r e t n i f o d n e p o t 3 13 d i v ) 1 ( ) b s m ( t u p n i g n i m m a r g o r p 4 12 d i v ) 1 ( t u p n i g n i m m a r g o r p 5 11 d i v ) 1 ( t u p n i g n i m m a r g o r p 6 10 d i v ) 1 ( ) b s l ( t u p n i g n i m m a r g o r p note: (1) all logic level inputs and outputs are open collector ttl compatible.
4 ? 2000 semtech corp. www.semtech.com power management SC1157 block diagram vid2 level shift and high side drive cs- cs+ vosense agnd d/a 70mv oscillator r s q bsth bstl + - vid1 + - current limit dh + - dl vid3 error amp pgnd en vid0 shoot-thru control vcc synchronous mosfet drive ref the voltage at the vosense pin is applied, through the internal precision resistor feedback chain, to the inverting input of the error amplifier. the non-inverting input of the error amplifier is supplied with a dc voltage derived by the dac from the internal trimmed bandgap voltage ref- erence. the output of the error amplifier is compared to the triangular output of the internal oscillator to generate a fixed frequency, variable duty cycle pulse train. the in- ternal oscillator uses an on-chip capacitor and precision trimmed current sources to set the frequency to 140 khz. the generated pulse train is gated with the output of the theory of operation current limit latch and the inhibit signal to produce a drive signal for the upper fet. it is also inverted to produce a drive signal for the lower fet. these fet drive signals are modified by the ?shoot-through control? circuitry so that the top fet turn-on is delayed until the bottom fet has turned off, and visa-versa. the current limit latch is set (ending the upper fet drive pulse early) if the current limit comparator indicates an overcurrent condition. the latch is reset at the start of each oscillator period.
5 ? 2000 semtech corp. www.semtech.com power management SC1157 vid table r e t e m a r a ps n o i t i d n o cd i v 0 1 2 3 n i mp y tx a ms t i n u e g a t l o v t u p t u o ) 1 ( i o d r a o b n o i t a u l a v e n i a 2 =1 1 1 17 8 2 . 10 0 3 . 13 1 3 . 1v 0 1 1 17 3 3 . 10 5 3 . 14 6 3 . 1 1 0 1 16 8 3 . 10 0 4 . 14 1 4 . 1 0 0 1 16 3 4 . 10 5 4 . 15 6 4 . 1 1 1 0 15 8 4 . 10 0 5 . 15 1 5 . 1 0 1 0 15 3 5 . 10 5 5 . 16 6 5 . 1 1 0 0 14 8 5 . 10 0 6 . 16 1 6 . 1 0 0 0 14 3 6 . 10 5 6 . 17 6 6 . 1 1 1 1 03 8 6 . 10 0 7 . 17 1 7 . 1 0 1 1 03 3 7 . 10 5 7 . 18 6 7 . 1 1 0 1 02 8 7 . 10 0 8 . 18 1 8 . 1 0 0 1 02 3 8 . 10 5 8 . 19 6 8 . 1 1 1 0 01 8 8 . 10 0 9 . 19 1 9 . 1 0 1 0 01 3 9 . 10 5 9 . 10 7 9 . 1 1 0 0 00 8 9 . 10 0 0 . 20 2 0 . 2 0 0 0 00 3 0 . 20 5 0 . 20 7 0 . 2 unless specified: vcc = 4.75v to 5.25v; gnd = pgnd = 0v; fb = v o ; 0mv < (cs+ - cs-) < 60mv; t j =0c to 85c
6 ? 2000 semtech corp. www.semtech.com power management SC1157 eval board schematic q7 irlr024n + c26 empty + c27 330uf q3 si4410 12v q2 si4410 j2 con4 1 2 3 4 r6 2.32k vid3 vlin2 c6 0.1uf SC1157 1.300 1.350 1.400 1.450 1.500 1.550 1.600 1.650 1.700 1.750 1.800 1.850 1.900 1.950 2.000 2.050 r20 100 100 100 r22 100 100 100 vccp j18 q1 si4410 5v vid0 r3 2.2 c1 0.1uf + c2 1500uf table valid for 1x5mohm sense resistor vlin1 r19 18.7 42.2 97.6 r21 18.7 42.2 97.6 r10 2.2 + c7 1500uf + c10 1500uf l1 2uh r7 5mohm phase j4 j16 scope tp r14 0 + c24 330uf c12 0.01uf j19 5v q5 si4410 s1 1 2 3 4 5 6 vid2 + c9 1500uf offset mv/v 0 2 2 2 5 5 5 10 10 10 r12 see table r2 empty c11 0.1uf r13 (ohm) empty 10 5 2 25 12.5 5 50 25 10 3.3v r20 see table + c8 1500uf sc1158 2.000 2.100 2.200 2.300 2.400 2.500 2.600 2.700 2.800 2.900 3.000 3.100 3.200 3.300 3.400 3.500 + - u2b lm358 5 6 7 8 4 j15 con4 1 2 3 4 r1 10 r19 see table r4 2.2 j13 j1 r8 2.2 r17 empty j5 j8 j17 r5 1.00k 12v r9 2.2 + c15 1500uf + c3 1500uf c13 0.1uf u1 SC1157cs 1 3 2 5 4 7 10 11 12 13 14 15 16 8 6 9 gnd vcc ref cs+ cs- dh bsth en vosense vid3 vid2 vid1 vid0 dl pgnd bstl r21 see table + c17 1500uf r13 see table droop mv/a 0 1 2 5 1 2 5 1 2 5 + c28 empty + - u2a lm358 3 2 1 8 4 vcc_core j6 j14 en 5v vlin1 1.5v 1.8v 2.5v vlin2 1.5v 1.8v 2.5v q6 irlr024n + c21 1500uf r16 1k c4 0.1uf j12 jumper settings shunt 1- 2 3- 4 vid 3210 1111 1110 1101 1100 1011 1010 1001 1000 0111 0110 0101 0100 0011 0010 0001 0000 + c25 330uf r22 see table j9 r18 5mohm q4 si4410 j12 1 3 2 4 + + + + c5 0.1uf . bstl supply 12v 5v r15 0 c14 empty r12 (ohm) 0 2.5 3.3 empty 6.3 8.3 empty 12.5 16.7 empty vid1
7 ? 2000 semtech corp. www.semtech.com power management SC1157 eval board gerber plots
8 ? 2000 semtech corp. www.semtech.com power management SC1157 m e t i. y t qe c n e r e f e re u l a vs e t o n 16 3 1 c , 1 1 c , 6 c , 5 c , 4 c , 1 cf u 1 . 0 29 , 7 1 c , 5 1 c , 0 1 c , 9 c , 8 c , 7 c , 3 c , 2 c 1 2 c f u 0 0 5 1t n e l a v i u q e r o x a - v m o y n a s r s e w o l 31 2 1 cf u 1 0 . 0 45 8 2 c , 6 2 c , 7 1 r , 4 1 c , 2 ry t p m e 53 7 2 c , 5 2 c , 4 2 cf u 0 3 3 61 1 lh u 2 2 5 - 0 6 t s l a t e m o r c i m n o g w a 6 1 s n r u t 6 e r o c 75 5 q , 4 q , 3 q , 2 q , 1 q0 1 4 4 i s 82 7 q , 6 qn 4 2 0 r l r i 91 1 r0 1 0 15 0 1 r , 9 r , 8 r , 4 r , 3 r2 . 2 1 11 5 rk 0 0 . 1% 1 2 11 6 rk 2 3 . 2% 1 3 12 7 r , 8 1 rm h o m 51 r a o c r i 4 16 2 2 r , 1 2 r , 0 2 r , 9 1 r , 3 1 r , 2 1 re l b a t e e s 5 12 5 1 r , 4 1 r0 6 11 6 1 rk 1 7 11 1 us c 7 5 1 1 c sh c e t m e s 8 11 2 u8 5 3 m l eval board bill of materials
9 ? 2000 semtech corp. www.semtech.com power management SC1157 semtech corporation power management products division 652 mitchell rd., newbury park, ca 91320 phone: (805)498-2111 fax (805)498-3804 outline drawing - so-16 contact information land pattern - so-16
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