Features

• Wide V_IN Range: 4V to 38V Operation
• R_SENSE 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 C_OUT
• Selectable Continuous, Pulse-Skipping or Burst Mode® Operation at Light Loads
• Low Shutdown I_Q: 20μA
• V_OUT Range: 0.8V to 5.5V
• Thermally Enhanced 16-Lead MSOP or 3mm × 3mm QFN Package

Typical Application

Description

The LTC3851-1 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 LTC3851-1 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 LTC3851-1 is identical to the LTC3851 except that the I_LIM pin is replaced by PGOOD.