power management 1 www.semtech.com SC1210 high speed, 12 v, synchronous power mosfet driver features applications august 8, 2003 the SC1210 is a high speed, dual output driver designed to drive high-side and low-side mosfets in a synchro- nous buck converter. these drivers can work with many semtech pwm controllers to provide a cost effective multi-phase voltage regulator for advanced micropro- cessors. a 30ns max propagation delay from input transition to the gate of the power fet?s guarantees operation at high switching frequencies. internal overlap protection circuit prevents shoot-through from vin to pgnd in the main and synchronous mosfets. the adaptive overlap pro- tection circuit ensures the bottom fet does not turn on until the top fet source has reached 1v, to prevent cross- conduction. 8.5v gate drive provides optimum enhancement of mosfets at minimum driver and mosfet switching loss. high current drive capability allows fast switching, thus reducing switching losses at high (up to 1.5mhz) frequen- cies without causing thermal stress on the driver. under-voltage-lockout and over-temperature shutdown features are included for proper protection and safe op- eration. timed latches and improved robustness are built into the safty functions such as the under voltage lock- out and adaptive shoot-through protection circuitry to prevent false triggering. the SC1210 is offered in a stan- dard so-8 package. high efficiency +12v supply voltage with internal ldo for optimum gate drive high peak drive current adaptive non-overlapping gate drives provide shoot-through protection fast rise and fall times (15ns typical with 3000pf load) ultra-low (<30ns) propagation delay (bg going low) floating top gate drive crowbar function for over voltage protection high frequency (to 1.5 mhz) operation allows use of small inductors and low cost ceramic capacitors under-voltage-lockout low quiescent current intel pentium tm processor power supplies amd athlon tm and k8 tm processor power supplies high current low voltage dc-dc converter s description typical application circuit c1 1uf r1 1r 0 c4 10u f r2 1r 0 l1 1 2 vi n (+12v) vout u1 sc 1210 1 2 3 4 5 6 7 8 dr n tg bs t co vin vr eg bg pgnd pwm q2 c3 1uf c5 d1 1n 4148 c2 1uf q1 r3 2r 2 c6 2.2 nf
2 ? 2003 semtech corp. www.semtech.com power management SC1210 electrical characteristics absolute maximum ratings unless specified: t a = 25c; v in = 12v; v reg = 8.5v r e t e m a r a pl o b m y ss n o i t i d n o cn i mp y tx a ms t i n u y l p p u s r e w o p e g a t l o v y l p p u sv n i 92 15 1v g n i t a r e p o , t n e r r u c t n e c s e i u qp o _ q i0 . 3a m t u o k c o l e g a t l o v r e d n u f o d l o h s e r h t t r a t sv g e r e g a t l o vv t r a t s _ g e r 43 . 4v s i s e r e t s y hs y h v o l v u 0 6 1v m o d l l a n r e t n i t u p t u o o d lv g e r v n i v 6 1 o t v 9 =5 . 8v e g a t l o v t u o p o r dv p o r d v n i v 8 . 8 o t v 5 =3 . 0v exceeding the specifications below may result in permanent damage to the device, or device malfunction. operation outside of th e parameters specified in the electrical characteristics section is not implied. r e t e m a r a pl o b m y ss n o i t i d n o cm u m i x a ms t i n u v n i e g a t l o v y l p p u sv n i 6 1v n r d o t t s bv n r d - t s b 1 1v d n g p o t t s bv d n g p - t s b 0 4v e s l u p d n g p o t t s bv e s l u p - t s b t e s l u p s n 0 0 1 <5 4v d n g p o t n r dv d n g p - n r d 0 3 o t 2 -v e s l u p d n g p o t n r dv e s l u p - n r d t e s l u p s n 0 0 2 <5 3 o t 5 -v t u p n i m w po c5 . 8 o t 3 . 0 -v 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 c j 0 4w / c e g n a r e r u t a r e p m e t n o i t c n u j g n i t a r e p ot 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 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
3 ? 2003 semtech corp. www.semtech.com power management SC1210 r e t e m a r a pl o b m y ss n o i t i d n o cn i mp y tx a ms t i n u o c e g a t l o v t u p n i h g i h c i g o lv h _ o c 0 . 2v e g a t l o v t u p n i w o l c i g o lv l _ o c 8 . 0v n w o d t u h s l a m r e h t t n i o p p i r t e r u t a r e p m e t r e v ot p t o 5 5 1c s i s e r e t s y ht t s y h 0 1c ) g t ( r e v i r d e d i s h g i h e c n a d e p m i t u p t u o r g t _ c r s v t s b v - n r d v 5 . 8 = 5 . 10 . 3 ? r g t _ k n i s 0 . 10 . 2 e m i t e s i rt g t _ r v , f n 3 = l c t s b v - n r d v 5 . 8 =5 1s n e m i t l l a ft g t _ f v , f n 3 = l c t s b v - n r d v 5 . 8 =0 1s n h g i h g n i o g g t , y a l e d n o i t a g a p o r pt g t _ h d p v t s b v - n r d v 5 . 8 =7 3s n w o l g n i o g g t , y a l e d n o i t a g a p o r pt g t _ l d p v t s b v - n r d v 5 . 8 =0 3s n ) g b ( r e v i r d e d i s - w o l e c n a d e p m i t u p t u o r g b _ c r s v t s b v - n r d v 5 . 8 = 5 . 10 . 3 ? r g b _ k n i s 5 . 10 . 3 e m i t e s i rt g b _ r v , f n 3 = l c t s b v - n r d v 5 . 8 =0 1s n e m i t l l a ft g b _ f v , f n 3 = l c t s b v - n r d v 5 . 8 =0 1s n h g i h g n i o g g b , y a l e d n o i t a g a p o r pt g b _ h d p v t s b v - n r d v 5 . 8 =0 2s n w o l g n i o g g b , y a l e d n o i t a g a p o r pt g b _ l d p v t s b v - n r d v 5 . 8 =7 2s n y a l e d e m i t t u o k c o l - e g a t l o v - r e d n u v g e r p u g n i p m a rt o l v u _ h d p 2s v g e r n w o d g n i p m a rt o l v u _ l d p 2s electrical characteristics (cont.) unless specified: t a = 25c; v in = 12v; v reg = 8.5v
4 ? 2003 semtech corp. www.semtech.com power management SC1210 timing diagrams co t pdl_bg t f_bg t pdh_tg t r_tg bg tg t pdl_tg t f_tg t pdh_bg t r_bg ris in g ed ge tr ans it ion falling edge transition dr n 1.4v 1.0v
5 ? 2003 semtech corp. www.semtech.com power management SC1210 pin configuration ordering information note: (1) only available in tape and reel packaging. a reel contains 2500 devices. 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 0 1 2 1 c s8 - o sc 5 2 1 o t 0 pin descriptions # n i pe m a n n i pn o i t c n u f n i p 1n r d . r e t r e v n o c k c u b s u o n o r h c n y s e h t f o ) e d o n g n i h c t i w s r o ( t e f s o m e d i s - w o l e h t f o e d o n n i a r d e h t 2g t. t e f s o m ) p o t ( g n i h c t i w s e h t r o f e v i r d e t a g t u p t u o 3t s b g n i t a o l f e h t p o l e v e d o t s n i p n r d d n a t s b n e e w t e b d e t c e n n o c s i r o t i c a p a c a . n i p p a r t s t o o b . ) c i m a r e c ( f 1 y l l a c i p y t s i e u l a v r o t i c a p a c e h t . t e f s o m e d i s - h g i h e h t r o f e g a t l o v p a r t s t o o b 4o c m h o k 0 5 l a n r e t n i n a . r e l l o r t n o c l a n r e t x e y b d e i l p p u s 0 1 2 1 c s e h t o t l a n g i s t u p n i m w p l e v e l c i g o l . d n g p o t n i p s i h t m o r f d e t c e n n o c s i r o t s i s e r 5n i v . r e t r e v n o c e h t f o l i a r r e w o p t u p n i o t t c e n n o c . o d l r o f r e w o p y l p p u s 6g e r v . ) m m 5 ( " 2 . 0 n a h t e r o m o n h t g n e l d a e l h t i w ) c i m a r e c ( f 7 . 4 o t f 1 h t i w e l p u o c e d . t u p t u o o d l 7g b. t e f s o m ) m o t t o b ( s u o n o r h c n y s e h t r o f e v i r d e t a g t u p t u o 8d n g p . e c r u o s s t e f s o m s u o n o r h c n y s e h t o t e s o l c n i p s i h t p e e k . d n u o r g top view (so-8) tg vreg bst 5 6 7 8 bg vin drn co pgnd 1 2 3 4
6 ? 2003 semtech corp. www.semtech.com power management SC1210 block diagram pgnd vreg tg ldo bst bg dr n co cont rol & ov erlap prot ection circ uit uv lo vin
7 ? 2003 semtech corp. www.semtech.com power management SC1210 applications information theor theor theor theor theor y of opera y of opera y of opera y of opera y of opera tion tion tion tion tion the SC1210 is a high speed, dual output driver designed to drive top and bottom mosfets in a synchronous buck converter. it features adaptive delay for shoot-through protection, vid-on-fly operation, and internal ldo for op- timum gate drive voltage. these drivers combined with variety of semtech pwm controllers form multi-phase voltage regulators for advanced microprocessors. uvlo uvlo uvlo uvlo uvlo a supply voltage has to be applied to vin pin of the SC1210. the top and bottom gates are held low until vin exceeds uvlo threshold of the driver. then the top gate remains low and the bottom gate is pulled high to turn on the bottom fet. gat gat gat gat gat e t e t e t e t e t ransition and shoo ransition and shoo ransition and shoo ransition and shoo ransition and shoo t thr t thr t thr t thr t thr ough pr ough pr ough pr ough pr ough pr o o o o o t t t t t ection ection ection ection ection refer to the timing diagrams section, the rising edge of the pwm input initiates the bottom fet turn-off and the top fet turn-on. after a short propagation delay (t pdl_bg ), the bottom gate begins to fall (t f_bg ). an adaptive circuit in the SC1210 monitors the bottom gate voltage to drop below 1.4v. then after a preset delay time (t pdh_tg ) is expired, the top gate turns on. the delay time is set to be 20ns typically. this prevents the top fet from turning on until the bottom fet is off. during the transition, the inductor current is freewheeling through the body diode of either bottom fet or top fet, upon the direction of the inductor current. the phase node could be low (ground) or high (vin). the falling edge of the pwm input controls the top fet turn-off and the bottom fet turn-on. after a short propa- gation delay (t pdl_tg ), the top gate begins to fall (t f_tg ). as the inductor current is commutated from the top fet to the body diode of the bottom fet, the phase node begins to fall. the adaptive circuit in the SC1210 de- tects the phase node voltage. it holds the bottom fet off until the phase node voltage has dropped below 1.0v. this prevents the top and bottom fets from conducting simultaneously or shoot-through. vid-on-fly operation vid-on-fly operation vid-on-fly operation vid-on-fly operation vid-on-fly operation certain new processors have required to changing the vid dynamically during the operation, or refered as vid- on-fly operation. a vid-on-fly can occur under light load or heavy load conditions. at light load, it could force the converter to sink current. upon turn-off of the top fet, the reversed inductor current has to be freewheeling through the body diode of the top fet instead of the bottom fet. as a result, the phase node voltage remains high. the SC1210 incorporates the ability by pulling the bottom gate to high internally, which over rides the adap- tive circuit and turns the bottom fet on. the delay time from the pwm falling egde to the bottom gate turn-on is set at 200ns typically. optimized gat optimized gat optimized gat optimized gat optimized gat e driv e driv e driv e driv e driv e v e v e v e v e v oltage oltage oltage oltage oltage with the supply voltage in between 9v to 16v, an inter- nal ldo is designed with the SC1210 to bring the volt- age to a lower level for gate drive. an external ceramic capacitor(1uf to 4.7uf) connected in between vreg to ground is needed to decouple the ldo. the ldo output powers up the low gate driver, and the high gate drive is powered by the external bootstrap circuit. the ldo out- put voltage is set at 8.5v. the manufacture data and bench tested results show that, for low r dson fets run at applied load current, the optimum gate drive voltage is around 8.5v, where the total power losses of power fets, including conduction loss, switching loss, and the gate drive loss, are minimized. thermal shut down thermal shut down thermal shut down thermal shut down thermal shut down the SC1210 will shut down by pulling both driver out- puts low if its junction temperature, t j , exceeds 155c. component selection component selection component selection component selection component selection bootstrap circuit bootstrap circuit bootstrap circuit bootstrap circuit bootstrap circuit the SC1210 uses an external bootstrap circuit to pro- vide a voltage for the top fet drive. this voltage, refer- ring to the phase node, is held up by a bootstrap ca- pacitor. typically, it is recommended to use a 1uf ceramic ca- pacitor with 25v rating and a commonly available diode in4148 for the bootstrap circuit. in addition, a small resistor may be added in between drn of the SC1210 and the phase node. the resistor is used to allievate the stress of the SC1210 from exposing to the negative spike on the drn pin. a negative spike could occur at
8 ? 2003 semtech corp. www.semtech.com power management SC1210 the phase node during the top fet turn-off due to para- sitic inductance in the switching loop. the spike could be minimized with a careful pcb layout. in those applica- tions with to-220 package fets, it is recommended to use a clamping diode on the drn pin to mitigate the impact of the excessive phase node negative spike. filters for supply power filters for supply power filters for supply power filters for supply power filters for supply power for vreg pin of the SC1210, it is recommended to use a 1uf to 4.7uf, 25v rating ceramic capacitor for decoupling. la la la la la y y y y y out guidelines out guidelines out guidelines out guidelines out guidelines the switching regulator is a high di/dt power circuit. its printed circuit board (pcb) layout is critical. a good lay- out can achieve an optimum circuit performance while minimized the component stress, resulting in better sys- tem reliability. for a multi-phase voltage regulator, the SC1210 driver, fets, inductor, and supply decoupling ca- pacitors in each phase have to be considered to yield a proper pcb layout. for the SC1210 driver, the following guidelines are typi- cally recommended during pcb layout: 1. place the SC1210 close to the fets for shortest gate drive traces and ground return paths. 2. connect bypass capacitors as close as possible to decoupling pins (vreg and vin) and pgnd. the trace length of the decoupling capacitor on vreg pin should be no more than 0.2? (5mm). 3. locate the components of the bootstrap circuit close to the SC1210. 4. provide a proper decoupling for the fets to reduce the inductive kick seen by the drn pin. applications information (cont.)
9 ? 2003 semtech corp. www.semtech.com power management SC1210 outline drawing - power soic-8 land pattern - soic-8 semtech corporation power management products division 200 flynn rd., camarillo, ca 93012 phone: (805)498-2111 fax (805)498-3804 contact information outline drawing - soic-8
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