1. Products
  2. Power Management
  3. Switching Regulators
  4. Step-Down (Buck) Regulators
  5. External Power Switch Buck Controllers
  6. LTC3851-1

Alternative Parts


Features and Benefits

  • 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

Product Details

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 ILIM pin is replaced by PGOOD.

LTC3851 Not Recommended For New Designs
LTC3851-1 Not Recommended For New Designs
LTC3851A Adjustable Current Limit
LTC3851A-1 PGOOD Output


  • Automotive Systems
  • Telecom Systems
  • Industrial Equipment
  • Distributed DC Power Systems

Product Lifecycle icon-recommended Production

At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.

Tools & Simulations


LTspice® is a powerful, fast and free simulation software, schematic capture and waveform viewer with enhancements and models for improving the simulation of analog circuits.


Models for the following parts are available in LTspice:



LTpowerCAD® is a power supply design program which selects power stage components, provides detailed power efficiency, shows quick loop Bode plot stability and load transient analysis, and can export to LTspice for simulation.


Design tools for the following parts are available in LTpowerCAD:


Product Recommendations

LTC3851-1 Companion Parts

Recommended Related Parts

Recommended Suggested Oscillator

Design Resources

ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well.  "Zero defects" for shipped products is always our goal.View our quality and reliability program and certifications for more information.

Part Number Material Declaration Reliability Data Pin/Package Drawing CAD Symbols, Footprints & 3D Models
LTC3851EMSE-1#PBF Material Declaration Reliability Data 16-Lead MSOP w/ EP
LTC3851EMSE-1#TRPBF Material Declaration Reliability Data 16-Lead MSOP w/ EP
LTC3851EUD-1#PBF Material Declaration Reliability Data 16-Lead QFN (3mm x 3mm x 0.75mm w/ EP)
LTC3851EUD-1#TRPBF Material Declaration Reliability Data 16-Lead QFN (3mm x 3mm x 0.75mm w/ EP)
LTC3851IMSE-1#PBF Material Declaration Reliability Data 16-Lead MSOP w/ EP
LTC3851IMSE-1#TRPBF Material Declaration Reliability Data 16-Lead MSOP w/ EP
Wafer Fabrication Data R526 Reliability Data

PCN-PDN Information

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Sample & Buy

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Buy Now Pricing

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List Pricing

(*)The 1Ku list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Analog Devices, Inc. authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.


Lead Times

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