power management 1 www.semtech.com SC1156 programmable synchronous dc/dc controller for advanced microprocessors features applications revision 4/01 typical application circuit description u low cost / full featured u synchronous operation u 5 bit vid dac programmable output u on-chip power good and ovp functions u designed to meet intel vrm8.1 (klamath) the SC1156 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 SC1156 is ideal for implementing dc/dc converters needed to power advanced microprocessors such as pentium ? ll (klamath), 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. SC1156 features include an integrated 5-bit vid dac, tem- perature compensated voltage reference, triangle wave oscillator, current limit comparator, frequency shift over-current protection, and an accessible, internally compensated error amplifier. power good signaling, logic compatible shutdown, and over voltage protection are also provided. the SC1156 operates at a fixed 200khz, providing an optimum compromise between efficiency, external com- ponent size, and cost. u pentium ? ii (klamath) core supply u multiple microprocessor supplies u voltage regulation modules (vrm) u programmable power supplies u high efficiency dc/dc conversion + c2 820uf r7 10k vid1 u1 SC1156cs 1 2 3 4 5 6 7 8 13 14 15 16 17 18 19 20 11 10 12 9 gnd vcc ovp pwrgood cs- cs+ pgndh dh bsth en vosense vid4 vid3 vid2 vid1 vid0 dl pgndl bstl nc vid2 12v in q2 irl3302s c9 0.1uf vid4 l1 4uh c12 0.1uf powergood ovp q1 irl3302s r6 10 c1 0.1uf r1 5mohm r4 1.00k vid3 + c4 820uf + c8 1500uf + c6 1500uf c10 0.1uf enable vid0 c11 0.1uf + c3 820uf r3 3.9 d1 1n4148 r5 2.32k + c5 1500uf r2 3.9 + c7 1500uf pentium ? ll power supply
2 ? 2000 semtech corp. www.semtech.com power management SC1156 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 d n g o t c c vv n i 5 1 + o t 3 . 0 -v d n g o t d n g p +1 v d n g o t t s b 6 2 + o t 3 . 0 -v 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 n o i t c n u jt j 5 2 1 + 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 + o t 5 6 -c e s a c 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 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 5 9w / 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 (unless otherwise noted: v cc = 11.4v to 12.6v; 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 oi o a 2 = ) 1 ( e l b a t e g a t l o v t u p t u o e e s e g a t l o v y l p p u sv c c 2 . 45 1v t n e r r u c y l p p u sv c c v 0 . 2 1 =5a 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 . 0% ) l o a ( n i a gv o t e s n e s o v o 5 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 0 8 10 0 20 2 2z h k e l c y c y t u d x a m r o t a l l i c s o 5 9% t n e r r u c e c r u o s / k n i s h dv 2 = 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 t s bv 2 = l d n g p - l d , v 5 . 4 = l d -1a e g a t l o v d l o h s e r h t p v o 0 2 1% t n e r r u c e c r u o s p v ov p v o v 3 =0 1a m e g a t l o v d l o h s e r h t d o o g r e w o p 0 90 1 1% e m i t d a e d 0 50 0 1s n note: (1) specification refers to typical application circuit
3 ? 2000 semtech corp. www.semtech.com power management SC1156 pin configuration ordering information pin descriptions # 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 2c c ve g a t l o v y l p p u s p i h c 3p v ov f i t u o l a n g i s h g i h o % 0 2 + t n i o p t e s > 4d o o g r w p ) 1 ( v f i h g i h , t u p t u o c i g o l r o t c e l l o c n e p o o t n i o p t e s f o % 0 1 n i h t i w 5- 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 6+ 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 7h d n g ph c t i w s e d i s h g i h r o f d n u o r g r e w o p 8h dt u p t u o r e v i r d e d i s h g i h 9c nd e t c e n n o c t o n 0 1l d n g ph c t i w s e d i s w o l r o f d n u o r g r e w o p 1 1l dt u p t u o r e v i r d e d i s w o l 2 1l t s b) t s o o b ( r e v i r d e d i s w o l r o f c c v 3 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 c c v 4 1n e ) 1 ( 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 5 1e s n e s o vk c a b d e e f 6 14 d i v ) 1 ( ) b s m ( t u p n i g n i m m a r g o r p 7 13 d i v ) 1 ( t u p n i g n i m m a r g o r p 8 12 d i v ) 1 ( t u p n i g n i m m a r g o r p 9 11 d i v ) 1 ( t u p n i g n i m m a r g o r p 0 20 d i v ) 1 ( ) b s l ( t u p n i g n i m m a r g o r p 1 2 3 4 5 6 7 8 vid0 gnd top view (20 pin soic) 13 14 15 16 vid1 vcc vid2 ovp vid3 pwrgood vid4 cs- vosense cs+ en pgndh bsth dh 9 10 12 bstl nc dl pgndl 11 18 17 19 20 note: (1) all logic inputs and outputs are open collector ttl compatible. 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 . w s 6 5 1 1 c s0 2 - o sc 5 2 1 o t 0 note: (1) only available in tape and reel packaging. a reel contains 1000 devices.
4 ? 2000 semtech corp. www.semtech.com power management SC1156 the d/a converter generates an output voltage determined by an internal trimmed bandgap voltage reference and the status of the vid0 through vid4 inputs. this voltage is applied to the non-inverting input of the error amplifier, the inverting input of the error amplifier is fed from the vosense pin via a precision resistor divider. the error amplifier itself is a transconductance amplifier with an in- ternal load resistor. the open loop gain is internally set to approximately 40 db. the internal oscillator uses an on-chip capacitor and a trimmed precision current source to set the frequency of oscillation to 200 khz. the triangular output of the oscil- lator is compared to the output of the error amplifier. the output of the pwm comparator is a pulse width modu- lated signal whose duty cycle increases as the voltage at the vosense pin decreases. the output of the current limit comparator goes high when theory of operation block diagram + - ovp d/a cs+ vid4 pgndh 70mv pwrgood dl + - bsth shutdown vcc gnd low side drive control vid2 oscillator cs- 1.25v ref en vosense + - bstdl + - current limit vid3 shoot-thru vid0 + - dh error amp pgndl level shift and drive r s q open collectors vcc vid1 + - its input voltage exceeds approximately 70mv, this sets the current limit latch, immediately terminating the cur- rent on time. the current limit latch is reset in the middle of the off time when the triangular wave oscillator reaches its highest point . when the output of the pwm comparator is high, output dh is driven high, provided that the vid code is valid, the current limit latch has not been set and the enable (en) pin is not pulled low. when the pwm comparator output is low dl is always driven high. the shoot-through control circuitry modifies the dh and dl waveforms slightly, ensuring that there is a short delay between one turning off and the other turning on. this ensures that the on times of the external fets driven by dh and dl do not overlap.
5 ? 2000 semtech corp. www.semtech.com power management SC1156 note: (1) all vid codes not specifically listed are invalid and cause shutdown exactly as if the shutdown pin had been asserted. output voltage 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 4 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 ) 1 e r u g i f ( t i u c r i c n o i t a c i l p p a n i a 2 =1 0 1 0 02 8 7 . 10 0 8 . 18 1 8 . 1v 0 0 1 0 02 3 8 . 10 5 8 . 18 6 8 . 1 1 1 0 0 01 8 8 . 10 0 9 . 19 1 9 . 1 0 1 0 0 01 3 9 . 10 5 9 . 19 6 9 . 1 1 0 0 0 00 8 9 . 10 0 0 . 20 2 0 . 2 0 0 0 0 00 3 0 . 20 5 0 . 20 7 0 . 2 1 1 1 1 10 8 9 . 10 0 0 . 20 2 0 . 2 0 1 1 1 19 7 0 . 20 0 1 . 21 2 1 . 2 1 0 1 1 18 7 1 . 20 0 2 . 22 2 2 . 2 0 0 1 1 17 7 2 . 20 0 3 . 23 2 3 . 2 1 1 0 1 16 7 3 . 20 0 4 . 24 2 4 . 2 0 1 0 1 15 7 4 . 20 0 5 . 25 2 5 . 2 1 0 0 1 14 7 5 . 20 0 6 . 26 2 6 . 2 0 0 0 1 13 7 6 . 20 0 7 . 27 2 7 . 2 1 1 1 0 12 7 7 . 20 0 8 . 28 2 8 . 2 0 1 1 0 11 7 8 . 20 0 9 . 29 2 9 . 2 1 0 1 0 10 7 9 . 20 0 0 . 30 3 0 . 3 0 0 1 0 19 6 0 . 30 0 1 . 31 3 1 . 3 1 1 0 0 18 6 1 . 30 0 2 . 32 3 2 . 3 0 1 0 0 17 6 2 . 30 0 3 . 33 3 3 . 3 1 0 0 0 16 6 3 . 30 0 4 . 34 3 4 . 3 0 0 0 0 15 6 4 . 30 0 5 . 35 3 5 . 3 unless otherwise noted: v cc = 4.75v to 5.25v; gnd = pgnd = 0v; fb = v o ; 0mv < (cs+ - cs-) < 60mv; t j = 25c
6 ? 2000 semtech corp. www.semtech.com power management SC1156 characteristic curves SC1156 regulation in application circuit -16 -14 -12 -10 -8 -6 -4 -2 0 0481216 output current (a) load regulation (mv) SC1156 efficiency in application circuit 3.5v 3.1v 2.8v 2.4v 2.1v 1.8v 70% 75% 80% 85% 90% 0 4 8 12 16 output current (a) efficiency (%) ripple at vo=2.00v; io=15a in application circuit transient at vo=2.00v; io= 0 to 15a in app. circuit
7 ? 2000 semtech corp. www.semtech.com power management SC1156 semtech corporation power management products division 652 mitchell rd., newbury park, ca 91320 phone: (805)498-2111 fax (805)498-3804 outline drawing - so-20 contact information ref. ms-013ac land pattern - so-20
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