LTC3851EMS Synchronous Step-Down Switching Regulator Controller

LTC3851EMS Synchronous Step-Down Switching Regulator Controller

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 n

Thermally Enhanced 16-Lead MSOP or 3mm × 3mm QFN Package

APPLICATIONS

Automotive Systems

Telecom Systems

Industrial Equipment

Distributed DC Power Systems

DESCRIPTION

The LTC®3851-1 is a high performance synchronous step-down switching regulator controller that drives an all N-channel synchronous power MOSFET stage. A con stant 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 confi gurations 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 ILIM pin is replaced by PGOOD.

TYPICAL APPLICATION

ABSOLUTE MAXIMUM RATINGS

Input Supply Voltage (VIN) ......................... 40V to –0.3V

Topside Driver Voltage (BOOST) ................ 46V to –0.3V

Switch Voltage (SW) ..................................... 40V to –5V

INTVCC, (BOOST – SW), RUN, PGOOD ........ 6V to –0.3V

TK/SS .................................................... INTVCC to –0.3V

SENSE+, SENSE– .......................................... 6V to –0.3V

MODE/PLLIN, FREQ/PLLFLTR ............... INTVCC to –0.3V

ITH, VFB Voltages .......................................... 3V to –0.3V

INTVCC Peak Output Current ..................................50mA

Operating Junction Temperature Range (Notes 2, 3) ............................................ –40°C to 125°C

Storage Temperature Range ................... –65°C to 150°C

Lead Temperature (Soldering, 10 sec) MSE .................................................................. 300°C

PIN CONFIGURATION

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