Datasheet LTC3707 (Analog Devices)

LTC3707 High Effi ciency, 2-Phase Synchronous Step-Down Switching Regulator
FEATURES DESCRIPTION
■
180° Phased Dual Controllers Reduce Required
The LTC®3707 is a high performance dual step-down
Input Capacitance and Power Supply Induced Noise
switching regulator controller that drives N-channel ■
OPTI-LOOP
®
Compensation Minimizes COUT
synchronous power MOSFET stages. A constant frequency ■ ±
1.5% Output Voltage Accuracy over Temperature
current mode architecture allows adjustment of the ■ Dual N-Channel MOSFET Synchronous Drive frequency up to 300kHz. Power loss and noise due to the ■ Power Good Output Voltage Monitor ESR of the input capacitors are minimized by operating ■ DC Programmed Fixed Frequency 150kHz to 300kHz the two controller output stages out of phase. ■ Wide VIN Range: 4.5V to 28V Operation OPTI-LOOP compensation allows the transient response to ■ Very Low Dropout Operation: 99% Duty Cycle be optimized over a wide range of output capacitance and ■ Adjustable Soft-Start Current Ramping ESR values. The precision 0.8V reference and power good ■ Foldback Output Current Limiting output indicator are compatible with future microprocessor ■ Latched Short-Circuit Shutdown with Defeat Option generations, and a wide 3.5V to 30V input supply range ■ Output Overvoltage Protection encompasses all battery chemistries. ■ Remote Output Voltage Sense ■ Low Shutdown I A RUN/SS pin for each controller provides both soft-start Q: 20μA ■ 5V and 3.3V Standby Regulators and optional timed, short-circuit shutdown. Current ■ Selectable Constant Frequency, Burst Mode® foldback limits MOSFET dissipation during short-circuit Operation or PWM Operation conditions when overcurrent latchoff is disabled. Output ■ Small 28-Lead Narrow SSOP Package overvoltage protection circuitry latches on the bottom
APPLICATIONS
MOSFET until VOUT returns to normal. The FCB mode pin can select among Burst Mode operation, constant ■ Notebook and Palmtop Computers, PDAs frequency mode and continuous inductor current mode ■ Battery Chargers or regulate a secondary winding. ■ Portable Instruments L, LT, LTC, LTM, Burst Mode, and OPTI-LOOP are registered trademarks of Linear Technology ■ Battery-Operated Digital Devices Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents including 5481178, 5705919, 5929620, 6144194, 6177787, 6304066, 6580258. ■ DC Power Distribution Systems
TYPICAL APPLICATION
VIN + C 5.2V TO 28V IN 1μF 4.7μF 22μF D3 D4 CERAMIC 50V VIN INTVCC CERAMIC M1 TG1 TG2 M3 L1 CB1, 0.1μF CB2, 0.1μF L2 6.3μH BOOST1 BOOST2 6.3μH SW1 SW2 LTC3707 D1 M2 BG1 BG2 M4 D2 SGND PGND SENSE1+ SENSE2+ RSENSE1 R 1000pF 1000pF SENSE2 0.01Ω 0.01Ω V SENSE1– SENSE2– OUT1 VOUT2 5V V 3.3V OSENSE1 VOSENSE2 5A R2 R4 5A 105k ITH1 ITH2 63.4k C C 1% C1 + COUT1 C2 1% COUT RUN/SS1 RUN/SS2 R3 + 47μF R1 220pF 220pF 56μF 6V 20k R 20k C1 R C C C2 SS1 SS2 6V SP 1% 15k 1% 15k 0.1μF 0.1μF SP M1, M2, M3, M4: FDS6680A 3707 F01
Figure 1. High Effi ciency Dual 5V/3.3V Step-Down Converter
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