LTC3851A - Synchronous Step-Down Switching Regulator Controller

Features

  • Wide VIN Range: 4V to 38V Operation
  • RSENSE 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 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, 16-Lead Narrow SSOP or 3mm × 3mm QFN Package

Typical Application

LTC3851A Typical Application
LTC3851A 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.

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

Packaging

For complete and up to date package information and drawings, please refer to our packaging page

MS-16, SSOP-16, QFN-16

LTC3851A Package Drawing
LTC3851A Package Drawing
LTC3851A Package Drawing

Order Info

Package Variations and Pricing

Part Number Package Pins Temp Price (1-99) Price (1k)* RoHS Data
LTC3851AEGN#PBF SSOP 16 E $2.44 $1.71 View
LTC3851AEGN#TRPBF SSOP 16 E $1.77 View
LTC3851AEMSE#PBF MSOP 16 E $2.44 $1.71 View
LTC3851AEMSE#TRPBF MSOP 16 E $1.77 View
LTC3851AEMSE-1#PBF MSOP 16 E $2.44 $1.71 View
LTC3851AEMSE-1#TRPBF MSOP 16 E $1.77 View
LTC3851AEUD#PBF QFN 16 E $2.44 $1.71 View
LTC3851AEUD#TRPBF QFN 16 E $1.71 View
LTC3851AEUD-1#PBF QFN 16 E $2.44 $1.71 View
LTC3851AEUD-1#TRPBF QFN 16 E $1.77 View
LTC3851AHMSE#PBF MSOP 16 H $3.20 $2.24 View
LTC3851AHMSE#TRPBF MSOP 16 H $2.30 View
LTC3851AHMSE-1#PBF MSOP 16 H $3.20 $2.24 View
LTC3851AHMSE-1#TRPBF MSOP 16 H $2.30 View
LTC3851AIGN#PBF SSOP 16 I $2.77 $1.94 View
LTC3851AIGN#TRPBF SSOP 16 I $2.00 View
LTC3851AIMSE#PBF MSOP 16 I $2.77 $1.94 View
LTC3851AIMSE#TRPBF MSOP 16 I $2.00 View
LTC3851AIMSE-1#PBF MSOP 16 I $2.77 $1.94 View
LTC3851AIMSE-1#TRPBF MSOP 16 I $2.00 View
LTC3851AIUD#PBF QFN 16 I $2.77 $1.94 View
LTC3851AIUD#TRPBF QFN 16 I $2.00 View
LTC3851AIUD-1#PBF QFN 16 I $2.77 $1.94 View
LTC3851AIUD-1#TRPBF QFN 16 I $2.00 View
LTC3851AMPMSE#PBF MSOP 16 MP $7.56 $5.29 View
LTC3851AMPMSE#TRPBF MSOP 16 MP $5.35 View
LTC3851AMPMSE-1#PBF MSOP 16 MP $7.56 $5.29 View
LTC3851AMPMSE-1#TRPBF MSOP 16 MP $5.35 View
LTC3851EGN#PBF SSOP 16 E $2.44 $1.71 View
LTC3851EGN#TRPBF SSOP 16 E $1.77 View
LTC3851EMSE#PBF MSOP 16 E $2.44 $1.71 View
LTC3851EMSE#TRPBF MSOP 16 E $1.77 View
LTC3851EMSE-1#PBF MSOP 16 E $2.44 $1.71 View
LTC3851EMSE-1#TRPBF MSOP 16 E $1.77 View
LTC3851EUD#PBF QFN 16 E $2.44 $1.71 View
LTC3851EUD#TRPBF QFN 16 E $1.77 View
LTC3851EUD-1#PBF QFN 16 E $2.44 $1.71 View
LTC3851EUD-1#TRPBF QFN 16 E $1.77 View
LTC3851IGN#PBF SSOP 16 I $2.77 $1.94 View
LTC3851IGN#TRPBF SSOP 16 I $2.00 View
LTC3851IMSE#PBF MSOP 16 I $2.77 $1.94 View
LTC3851IMSE#TRPBF MSOP 16 I $2.00 View
LTC3851IMSE-1#PBF MSOP 16 I $2.77 $1.94 View
LTC3851IMSE-1#TRPBF MSOP 16 I $2.00 View
LTC3851IUD#PBF QFN 16 I $2.77 $1.94 View
LTC3851IUD#TRPBF QFN 16 I $2.00 View
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* The USA 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 Linear Technology sales office or authorized distributor.

Demo Boards

Linear Technology offers many demo boards free of charge to qualified customers. Contact your local sales office or distributor to inquire about a demo board. Certain demo boards are also available for sale via credit card on this website. Demo boards are for evaluation purposes only. It remains the customer’s responsibility to verify proper and reliable operation in the actual end application.

Part Number Description Price Documentation
DC1432A-A LTC3851AUED Demo Board with Adj ILIMIT | 4.5V ≤ VIN ≤ 14V, VOUT = 1.5V @ 15A. $100.00
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Click here to view our complete list of demo boards

Applications

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

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Design Tools

LTpowerCAD

The LTpowerCAD II design tool is a complete power supply design tool program that can significantly ease the tasks of power supply design. It guides users to a solution, selects power stage components, provides detailed power efficiency, shows quick loop bode plot stability and load transient analysis, and can export a final design to LTspice for simulation. Click here to download LTpowerCAD

Design tools for the following parts are available in LTpowerCAD:
LTC3851A

LTspiceIV

LTspice IV is a powerful, fast and free simulation tool, schematic capture and waveform viewer with enhancements and models for improving the simulation of switching regulators. Click here to download LTspice IV

To launch a ready to run LTspice demonstration circuit for this part:

  • Step 1: If you have not installed LTspice on this computer, download and install LTspice IV
  • Step 2: Once LTspice is installed, click on the link(s) below to launch the simulation
  • Step 3: If LTspice IV does not automatically open after clicking the link above, you can instead run the simulation by right clicking on the link and selecting "Save Target As". After saving the file to your computer, start LTspice and open the demonstration circuit by selecting 'Open' from the 'File' menu

To explore other ready to run LTspice demonstration circuits, please visit our Demo Circuits Collection.

Models for the following parts are available in LTspice IV:
LTC3851
LTC3851-1
LTC3851A
LTC3851A-1

Technical Support