Synchronous Step-Down Switching Regulator Controller

The LTC3851A-1 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-1 features a precision 0.8V reference and a power good indicator. A wide 4V to 38V (40V absolute maximum) input supply range encompasses most battery configurations and intermediate bus voltages.

The TK/SS pin ramps the output voltage during start-up and shutdown with coincident or ratiometric tracking. 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-1 contains an improved PLL compared to the LTC3851-1.

The LTC3851A-1 is identical to the LTC3851A except that the ILIM pin is replaced by PGOOD.

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

* Power Good Output Voltage Monitor

* 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