Datasheet LTC3727, LTC3727-1 (Analog Devices)

LTC3727/LTC3727-1 High Efficiency, 2-Phase Synchronous Step-Down Switching Regulators
U FEATURES DESCRIPTIO
■
Wide Output Voltage Range: 0.8V
≤
VOUT
≤
14V
The LTC®3727/LTC3727-1 are high performance dual ■
Out-of-Phase Controllers Reduce Required Input
step-down switching regulator controllers that drive all
Capacitance and Power Supply Induced Noise
N-channel synchronous power MOSFET stages. A con- ■
OPTI-LOOP® Compensation Minimizes COUT
stant frequency current mode architecture allows phase- ■ ±
1% Output Voltage Accuracy
lockable frequency of up to 550kHz. Power loss and noise ■
Power Good Output Voltage Monitor
due to the ESR of the input capacitors are minimized by ■
Phase-Lockable Fixed Frequency 250kHz to 550kHz
operating the two controller output stages out of phase. ■ Latched Short-Circuit Shutdown (LTC3727 Only) OPTI-LOOP compensation allows the transient response ■ Dual N-Channel MOSFET Synchronous Drive to be optimized over a wide range of output capacitance and ■ Wide VIN Range: 4V to 36V Operation ESR values. There is a precision 0.8V reference and a power ■ Very Low Dropout Operation: 99% Duty Cycle good output indicator. A wide 4V to 30V (36V maximum) ■ Adjustable Soft-Start Current Ramping input supply range encompasses all battery chemistries. ■ Foldback Output Current Limiting ■ Output Overvoltage Protection A RUN/SS pin for each controller provides soft-start, and ■ Low Shutdown I on the LTC3727GN, optional timed, short-circuit shut- Q: 20μA ■ Selectable Constant Frequency or Burst Mode® down. Current foldback limits MOSFET heat dissipation Operation during short-circuit conditions when overcurrent latchoff ■ Small 28-Lead SSOP Package is disabled. Output overvoltage protection circuitry latches ■ LTC3727-1 Also Available in the 5mm × 5mm QFN on the bottom MOSFET until VOUT returns to normal. The Package FCB mode pin can select among Burst Mode, constant
U
frequency mode and continuous inductor current mode or
APPLICATIO S
regulate a secondary winding. ■ Telecom Systems , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. Burst Mode and OPTI-LOOP are registered trademarks of Linear Technology Corporation. All other ■ Automotive Systems trademarks are the property of their respective owners. Protected by U.S. Patents, including 5481178, 5929620, 6177787, 6144194, 6100678, 5408150, 6580258, 6304066, 5705919. ■ Battery-Operated Digital Devices
U TYPICAL APPLICATIO
VIN + 18V TO 28V 22μF 1μF 4.7μF 50V CERAMIC V CERAMIC IN PGOOD INTVCC M1 TG1 TG2 M3 0.1μF 8μH BOOST1 BOOST2 15μH 0.1μF SW1 SW2 LTC3727/ M2 BG1 BG2 M4 LTC3727-1 PLLIN PGND SENSE1+ SENSE2+ 1000pF 0.015Ω 1000pF 0.015Ω SENSE1– SENSE2– VOUT1 VOUT2 5V VOSENSE1 VOSENSE2 12V 5A 105k 280k 4A 1% ITH1 ITH2 1% + 220pF + 56μF 47μF RUN/SS1 RUN/SS2 220pF SGND 20k 20k 15V 6V 1% 1% SP SP 15k 15k 0.1μF 0.1μF M1, M2, M3, M4: FDS6680A 3727 F01
Figure 1. High Efficiency Dual 12V/5V Step-Down Converter
3727fc 1