Synchronous Step-Down Switching Regulator Controller

The LTC3851A is a high performance synchronous step-down switching regulator controller that drives an all N-channel synchronous power MOSFET stage. A constant frequency current mode architecture allows a phase-lockable frequency of up to 750kHz.

OPTI-LOOP compensation allows the transient response to be optimized over a wide range of output capacitance and ESR values. The LTC3851A features a precision 0.8V reference that is compatible with a wide 4V to 38V input supply range.

The TK/SS pin ramps the output voltage during start-up. Current foldback limits MOSFET heat dissipation during short-circuit conditions. The MODE/PLLIN pin selects among Burst Mode operation, pulse-skipping mode or continuous inductor current mode at light loads and allows the IC to be synchronized to an external clock. The LTC3851A contains an improved PLL compared to the LTC3851.

The LTC3851A-1 is a version with a power good output signal instead of adjustable current limit.

Features

LTC3851

Not Recommended For New Designs

LTC3851-1

Not Recommended For New Designs

LTC3851A

Adjustable Current Limit

LTC3851A-1

PGOOD Output

Applications

* Automotive Systems

* Telecom Systems

* Industrial Equipment

* Distributed DC Power Systems

* Wide VIN Range: 4V to 38V Operation

* RSENSE or DCR Current Sensing

* ±1% Output Voltage Accuracy

* Phase-Lockable Fixed Frequency: 250kHz to 750kHz

* Dual N-Channel MOSFET Synchronous Drive

* Very Low Dropout Operation: 99% Duty Cycle

* Adjustable Output Voltage Soft-Start or Tracking

* Output Current Foldback Limiting

* Output Overvoltage Protection