LTC3861 - Dual, Multiphase Step-Down Voltage Mode DC/DC Controller with Accurate Current Sharing


  • Operates with Power Blocks, DrMOS or External Gate Drivers and MOSFETs
  • Constant-Frequency Voltage Mode Control with Accurate Current Sharing
  • ±0.75% 0.6V Voltage Reference
  • Dual Differential Output Voltage Sense Amplifiers
  • Multiphase Capability—Up to 12-Phase Operation
  • Programmable Current Limit
  • Safely Powers a Prebiased Load
  • Programmable or PLL-Synchronizable Switching Frequency Up to 2.25MHz
  • Lossless Current Sensing Using Inductor DCR or Precision Current Sensing with Sense Resistor
  • VCC Range: 3V to 5.5V
  • VIN Range: 3V to 24V
  • Power Good Output Voltage Monitor
  • Output Voltage Tracking Capability
  • Programmable Soft-Start
  • Available in a 36-Pin 5mm × 6mm QFN Package

Typical Application

LTC3861 Typical Application


The LTC®3861 is a dual PolyPhase® synchronous stepdown switching regulator controller for high current distributed power systems, digital signal processors, and other telecom and industrial DC/DC power supplies. It uses a constant-frequency voltage mode architecture combined with very low offset, high bandwidth error amplifiers and a remote output sense differential amplifier per channel for excellent transient response and output regulation.

The controller incorporates lossless inductor DCR current sensing to maintain current balance between phases and to provide overcurrent protection. The chip operates from a VCC supply between 3V and 5.5V and is designed for stepdown conversion from VIN between 3V and 24V to output voltages between 0.6V and VCC – 0.5V.

The TRACK/SS pins provide programmable soft-start or tracking functions. Inductor current reversal is disabled during soft-start to safely power prebiased loads. The constant operating frequency can be synchronized to an external clock or linearly programmed from 250kHz to 2.25MHz. Up to six LTC3861 controllers can operate in parallel for 1-, 2-, 3-, 4-, 6- or 12-phase operation.

The LTC3861 is available in a 36-pin 5mm × 6mm QFN package. LTC3861-1 is a 32-pin QFN version of the LTC3861, which has a single differential remote output voltage sense amplifier.

  # Diff Amps
Config Pin Package
LTC3861 2 Yes 5 x 6 QFN-36
LTC3861-1 1 No 5 x 5 QFN-32


CAD Symbols and Footprints: The downloadable Zip file below contains the schematic symbol and PCB footprints.

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

Part Number Package Code Temp Package
LTC3861EUHE#PBF 5x6 QFN-36 UHE E 05-08-1876 Yes
LTC3861EUHE#TRPBF 5x6 QFN-36 UHE E 05-08-1876 Yes
LTC3861IUHE#PBF 5x6 QFN-36 UHE I 05-08-1876 Yes
LTC3861IUHE#TRPBF 5x6 QFN-36 UHE I 05-08-1876 Yes

LTC3861 Package Drawing

Order Info

  • Part numbers ending in PBF are lead free. Solder plated terminal finish (SnPb) versions are non-standard and special terms and conditions and pricing applies if available. Please contact LTC marketing for information.
  • Part numbers containing TR or TRM are shipped in tape and reel or 500 unit mini tape and reel, respectively
  • Please refer to our general ordering information or the product datasheet for more details

Package Variations and Pricing

Part Number Package Temp Price
LTC3861EUHE#PBF 5x6 QFN-36 E $4.11 $2.88 Yes
LTC3861EUHE#TRPBF 5x6 QFN-36 E $2.94 Yes
LTC3861IUHE#PBF 5x6 QFN-36 I $4.54 $3.18 Yes
LTC3861IUHE#TRPBF 5x6 QFN-36 I $3.24 Yes
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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
DC1822A LTC3861EUHE with DrMOS Demo Board | 7V ≤ VIN ≤ 14V; VOUT1 = 1.5V @ 25A, VOUT2 = 1.2V @ 25A $250.00
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Click here to view our complete list of demo boards


  • High Current Distributed Power Systems
  • DSP, FPGA and ASIC Supplies
  • Datacom and Telecom Systems
  • Industrial Power Supplies

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Design Tools


LTspice® software 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

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The LTpowerCAD 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

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LTC3861 Parallel

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