LTC3713 Low Input Voltage, TM High Power, No R SENSE Synchronous Buck DC/DC Controller FEATURES DESCRIPTIO n Very Low V : 1.5V The LTC 3713 is a high current, high efficiency synchro- IN(MIN) n True Current Mode Control nous buck switching regulator controller optimized for n 5V Drive for N-Channel MOSFETs Eliminates use with very low input supply voltages. It operates from Auxillary 5V Supply inputs as low as 1.5V and provides a regulated output n No Sense Resistor Required voltage from 0.8V up to (0.9)V . The controller uses IN n Uses Standard 5V Logic-Level N-Channel MOSFETs a valley current control architecture to enable high operat- n Adjustable Current Limit ing frequencies without requiring a sense resistor. n Adjustable Frequency Operating frequency is selected by an external resistor and n Switch t < 100ns is compensated for variations in V and V . The LTC3713 ON(MIN) IN OUT n 2% to 90% Duty Cycle at 200kHz uses a pair of standard 5V logic-level N-channel external n 0.8V 1% Reference MOSFETs, eliminating the need for expensive P-channel n Power Good Output Voltage Monitor or low threshold devices. n Programmable Soft-Start Discontinuous mode operation provides high efficiency n Output Overvoltage Protection operation at light loads. A forced continuous control n Optional Short-Circuit Shutdown Timer pin reduces noise and RF interference, and can assist n Small 24-Lead SSOP Package secondary winding regulation by disabling discontinuous U operation when the main output is lightly loaded. Fault APPLICATIO S protection is provided by internal foldback current limit- n Telecom Card 3.3V, 2.5V, 1.8V Step-Down ing, an output overvoltage comparator and an optional n Bus Termination (DDR memory, SSTL) short-circuit shutdown timer. n Synchronous Buck with General Purpose Boost , LTC and LT are registered trademarks of Linear Technology Corporation. n No R is a trademark of Linear Technology Corporation. Low V Synchronous Boost SENSE IN TYPICAL APPLICATIO V IN 1.8V TO 3.3V CMDSH-3 22F 2 Efficiency vs Load Current SHDN BOOST 330k 0.33F 100 5.6k V = 2.5V IN I TG M1 ON L1 90 LTC3713 1.8H V OUT A 1.25V 80 V SW1 FB1 B 10A + C + OUT 70 SENSE 10k 270F 680pF BG M2 2 60 B340A 20k I PGND 50 TH SENSE 40 10F RUN/SS INTV CC 30 0.1F PGOOD V IN1 20 3713 F01a SGND V IN2 10 4.7F C : PANASONIC EEFUEOD271R 0 MBR0520 OUT 4.7H 12 0.01 0.04 0.10 0.40 1 3 7 15 L1: (A) PANASONIC ETQP6FIR8BFA (B) TOKO D104C-1.8H LOAD CURRENT (A) V SW2 FB2 M1, M2: (A) IRF7822, (B) IRF7811A 3713 F01b 12.1k 37.4k Figure 1. High Efficiency Step-Down Converter from 1.8V to 3.3V Input 3713fa 1 EFFICIENCY (%) U ULTC3713 UUW ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO (Note 1) Input Supply Voltage (V ) .......................10V to 0.3V ORDER PART TOP VIEW IN2 NUMBER Boosted Topside Driver Supply Voltage 1 24 BOOST RUN/SS (BOOST) ............................................... 42V to 0.3V 2 23 TG V ON LTC3713EG + V , I , SW1, SENSE Voltages ............. 36V to 0.3V 3 22 SW1 IN1 ON PGOOD + RUN/SS, PGOOD Voltages ......................... 7V to 0.3V 4 21 SENSE V RNG FCB, V , V Voltages .......... INTV + 0.3V to 0.3V 5 20 SENSE FCB ON RNG CC 6 19 PGND1 I , V , SENSE Voltages ..................... 2.7V to 0.3V I TH TH FB1 7 18 BG SGND1 SW2 Voltage ............................................. 36V to 0.4V 8 17 INTV I CC ON V Voltage ................................................. V + 0.3V FB2 IN2 9 16 V V IN1 FB1 SHDN Voltage ......................................................... 10V 10 15 V SHDN IN2 TG, BG, INTV Peak Currents.................................. 2A CC 11 14 PGND2 SGND2 TG, BG, INTV RMS Currents ............................ 50mA CC 12 13 SW2 V FB2 Operating Ambient Temperature G PACKAGE Range (Note 4) ................................... 40 C to 85 C 24-LEAD PLASTIC SSOP Junction Temperature (Note 2)............................ 125 C T = 125 C, q = 130 C/ W JMAX JA Storage Temperature Range ................. 65 C to 150 C Consult LTC Marketing for parts specified with wider operating temperature ranges. Lead Temperature (Soldering, 10 sec).................. 300 C ELECTRICAL CHARACTERISTICS The l denotes specifications which apply over the full operating temperature range, otherwise specifications are T = 25 C. V = 15V, V = 1.5V unless otherwise noted. A IN1 IN2 SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Buck Regulator I Input DC Supply Current (V ) Q(VIN1) IN1 Normal 900 2000 m A Shutdown Supply Current 15 30 m A V Feedback Reference Voltage I = 1.2V (Note 3) l 0.792 0.800 0.808 V FB1 TH I Feedback Current (Note 3) 5 50 nA FB1 D V Feedback Voltage Line Regulation V = 4V to 30V, I = 1.2V (Note 3) 0.002 %/V FB1(LINEREG) IN1 TH D V Feedback Voltage Load Regulation I = 0.5V to 1.9V (Note 3) l 0.05 0.3 % FB1(LOADREG) TH g Error Amplifier Transconductance I = 1.2V (Note 3) l 1.4 1.7 2 mS m(EA) TH V Forced Continuous Threshold l 0.76 0.8 0.84 V FCB I Forced Continuous Pin Current V = 0.8V 1 2 m A FCB FCB t On-Time I = 60m A, V = 1.5V 200 250 300 ns ON ON ON I = 30m A, V = 1.5V 400 500 600 ns ON ON t Minimum On-Time I = 180m A 50 100 ns ON(MIN) ON t Minimum Off-Time 250 400 ns OFF(MIN) V Maximum Current Sense Threshold V = 1V, V = 0.76V l 113 133 153 mV SENSE(MAX) RNG FB1 V V V = 0V, V = 0.76V l 79 93 107 mV PGND SW RNG FB1 V = INTV , V = 0.76V l 158 186 214 mV RNG CC FB1 V Minimum Current Sense Threshold V = 1V, V = 0.84V 67 mV SENSE(MIN) RNG FB1 V V V = 0V, V = 0.84V 47 mV PGND SW RNG FB1 V = INTV , V = 0.84V 93 mV RNG CC FB1 D V Output Overvoltage Fault Threshold 5.5 7.5 9.5 % FB1(OV) D V Output Undervoltage Fault Threshold 520 600 680 mV FB1(UV) V RUN Pin Start Threshold l 0.8 1.5 2 V RUN/SS(ON) V RUN Pin Latchoff Enable Threshold RUN/SS Pin Rising 4 4.5 V RUN/SS(LE) V RUN Pin Latchoff Threshold RUN/SS Pin Falling 3.5 4.2 V RUN/SS(LT) 3713fa 2 U WWW