LTC3851EUD-PBF Step-Down SwitchingRegulator Controller

FEATURES

Wide VIN Range: 4V to 38V

Operation n RSENSE or DCR

Current Sensing n ±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 n 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

16-Lead Narrow SSOP or 3mm × 3mm QFN Package

APPLICATIONS

Automotive Systems

Telecom Systems

Industrial Equipment

Distributed DC Power Systems

DESCRIPTION

The LTC®3851 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 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.

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

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

TK/SS, ILIM ............................................ 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 Temperature Range (Note 2).... –40°C to 85°C

Junction Temperature (Note 3) ............................. 125°C

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

UD .........................................................–65 to 125°C

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

PIN CONFIGURATION

ORDER INFORMATION

Consult LTC Marketing for parts specifi ed with wider operating temperature ranges. Consult LTC Marketing for information on non-standard lead based fi nish parts. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifi cations, go to: http://www.linear.com/tapeandreel/

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