LINEAR TECHNOLOGY LTC3727 LTC3727-1 User's Manual

LTC3727/LTC3727-1 High Efficiency, 2-Phase

Synchronous Step-Down Switching Regulators

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 550k Hz. Power loss and noise

Power Good Output Voltage Monitor due to the ESR of the input capacitors are minimized by Phase-Lockable Fixed Frequency 250k Hz to 550k Hz 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 IQ: 20µA on the LTC3727GN, optional timed, short-circuit shut- 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 frequency mode and continuous inductor current mode or

APPLICATIO S regulate a secondary winding.

, LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode

Telecom Systems

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

TYPICAL APPLICATIO

VIN 18V TO 28V 22µF

CERAMIC

VIN PGOOD INTVCC CERAMIC

M1 TG1 TG2 M3

8µH BOOST1 BOOST2 15µH

SW1 SW2 LTC3727/

M2 BG1 LTC3727-1 BG2 M4

PLLIN PGND

SENSE1+ SENSE2+

SENSE1– SENSE2–

VOUT1 VOUT2

5V VOSENSE1 VOSENSE2 12V

1% ITH1 ITH2

47µF 220p F RUN/SS1 SGND RUN/SS2 220p F 20k

1% 15k 15k SP

SP 0.1µF 0.1µF

M1, M2, M3, M4: FDS6680A

Figure 1. High Efficiency Dual 12V/5V Step-Down Converter

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