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LTC3851A-1 - 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 shortcircuit 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 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 Output Current Foldback Limiting Output Overvoltage Protection OPTI-LOOP® Compensation Minimizes COUT Selectable Continuous, Pulse-Skipping or Burst Mode® Operation at Light Loads Low Shutdown IQ: 20μA VOUT Range: 0.8V to 5.5V Thermally Enhanced 16-Lead MSOP or 3mm × 3mm QFN Package Typical Application

Applications Automotive Systems Telecom Systems Industrial Equipment Distributed DC Power Systems Packaging

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