Features

• Wide V_IN Range: 4V to 38V Operation
• R_SENSE 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
• 5V Internal Regulator
• 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, 16-Lead Narrow SSOP or 3mm × 3mm QFN Package

Typical Application

Description

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.