LTC3861

RECOMMENDED FOR NEW DESIGNS

LTC3861

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

RECOMMENDED FOR NEW DESIGNS

Not the part you were looking for?

Go to Product Selection Table

View All Documentation

Ask a Question

Submit your question below and we will return the best answer from ADI’s knowledge database:

Other places you can find help

Support

Analog Devices Support Portal is a one-stop shop to answer all your ADI questions.

Visit the ADI Support Page

Ask the ADI community for help.

Ask the EngineerZone Community

FAQs

Sales & Ordering FAQs

Part Models 4

1ku List Price Starting From $3.46

Features

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
V_CC Range: 3V to 5.5V
V_IN 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

Additional Details

The LTC3861 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 V_CC supply between 3V and 5.5V and is designed for stepdown conversion from V_IN between 3V and 24V to output voltages between 0.6V and V_CC – 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

Applications

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

View All Documentation

Ask a Question

Submit your question below and we will return the best answer from ADI’s knowledge database:

Other places you can find help

Support

Analog Devices Support Portal is a one-stop shop to answer all your ADI questions.

Visit the ADI Support Page

Ask the ADI community for help.

Ask the EngineerZone Community

FAQs

Sales & Ordering FAQs

Part Models 4

1ku List Price Starting From $3.46

Technical Documents 7

LTC3861: Dual, Multiphase Step-Down Voltage Mode DC/DC Controller with Accurate Current Sharing Data Sheet 04/22/2015

R415 Reliability Data 03/23/2018

DC1822A - Demo Manual 06/14/2012

AN149 - Modeling and Loop Compensation Design of Switching Mode Power Supplies 02/04/2016

AN-140: Basic Concepts of Linear Regulator and Switching Mode Power Supplies 09/01/2019

Flexible, Dual Output, 6-Phase Buck Controller Drives 12 V to 1.0 V/200 A Core Supply with 90.0% Efficiency 11/01/2020

Sub-Milliohm DCR Current Sensing with Accurate Multiphase Current Sharing for High Current Power Supplies 01/01/2013

Reference Materials 1

How Monolithic Driver + MOSFET (DrMOS) Technology Improves Power System Design 06/01/2022

Design Resources 4

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 Model	Pin/Package Drawing	Documentation	CAD Symbols, Footprints, and 3D Models
LTC3861EUHE#PBF	36-Lead QFN (5mm x 6mm x 0.75mm w/ EP)	HTML Material Declaration HTML Reliablity Data	Ultra Librarian SamacSys
LTC3861EUHE#TRPBF	36-Lead QFN (5mm x 6mm x 0.75mm w/ EP)	HTML Material Declaration HTML Reliablity Data	Ultra Librarian SamacSys
LTC3861IUHE#PBF	36-Lead QFN (5mm x 6mm x 0.75mm w/ EP)	HTML Material Declaration HTML Reliablity Data	Ultra Librarian SamacSys
LTC3861IUHE#TRPBF	36-Lead QFN (5mm x 6mm x 0.75mm w/ EP)	HTML Material Declaration HTML Reliablity Data	Ultra Librarian SamacSys

LTC3861EUHE#PBF
Pin/Package Drawing
36-Lead QFN (5mm x 6mm x 0.75mm w/ EP)
Documentation

HTML Material Declaration

HTML Reliablity Data

CAD Symbols, Footprints, and 3D Models
Ultra Librarian
SamacSys

LTC3861EUHE#TRPBF
Pin/Package Drawing
36-Lead QFN (5mm x 6mm x 0.75mm w/ EP)
Documentation

HTML Material Declaration

HTML Reliablity Data

CAD Symbols, Footprints, and 3D Models
Ultra Librarian
SamacSys

LTC3861IUHE#PBF
Pin/Package Drawing
36-Lead QFN (5mm x 6mm x 0.75mm w/ EP)
Documentation

HTML Material Declaration

HTML Reliablity Data

CAD Symbols, Footprints, and 3D Models
Ultra Librarian
SamacSys

LTC3861IUHE#TRPBF
Pin/Package Drawing
36-Lead QFN (5mm x 6mm x 0.75mm w/ EP)
Documentation

HTML Material Declaration

HTML Reliablity Data

CAD Symbols, Footprints, and 3D Models
Ultra Librarian
SamacSys

Companion Parts 4

Parts	Product Life Cycle	Description
Digital Power System Managers1
LTC2974	RECOMMENDED FOR NEW DESIGNS	4-Channel PMBus Power System Manager Featuring Accurate Output Current Measurement
Dual-Supply Monitors1
LTC2960	RECOMMENDED FOR NEW DESIGNS	36V Nano-Current Two-Input Voltage Monitor
Multiple Output Buck Regulators1
LTC3880	RECOMMENDED FOR NEW DESIGNS	Dual Output PolyPhase Step-Down DC/DC Controller with Digital Power System Management
Surge Stopper, Overvoltage, and Overcurrent Protection1
LT4363	RECOMMENDED FOR NEW DESIGNS	High Voltage Surge Stopper with Current Limit

Alternative Parts 2

Parts	Product Life Cycle	Description
LTC3861-1	RECOMMENDED FOR NEW DESIGNS	Dual, Multiphase Step-Down Voltage Mode DC/DC Controller with Accurate Current Sharing
LTC7851	RECOMMENDED FOR NEW DESIGNS	Quad Output, Multiphase Step-Down Voltage Mode DC/DC Controller with Accurate Current Sharing

DC1822B

LTC3861 Demo Board | High Current, Dual Output Synchronous Buck Converter

LTC3861 Demo Board | High Current, Dual Output Synchronous Buck Converter

Download

DC1822B

LTC3861 Demo Board | High Current, Dual Output Synchronous Buck Converter

Features and Benefits

Remote sensing for each output, where the divider is placed before a high input impedance differential amplifier.
CLKIN and CLKOUT pins.
Optional resistors to tie the two outputs together.
Connector and header to tie two or more boards together for up to 12-phase operation.
Optional footprint for an LTC4449 gate driver and discrete MOSFETs.
Optional footprint for a dual phase Delta power block.

Buy Now View Details

Product Detail

Demonstration circuit 1822B is a dual output synchronous buck converter featuring the LTC3861EUHE. The board provides two outputs of 1.5V/25A and 1.2V/25A from an input voltage of 7V to 14V at a switching frequency of 500kHz. The power stage consists of a 6mm × 6mm DrMOS and a 13mm × 13mm iron powder type inductor. An on-board 5V LT3470 buck regulator provides the 5V bias for the LTC3861 and the DrMOS.

The demo board uses a high density, two sided drop-in layout. The power components, excluding the bulk output and input capacitors, fit within a 1.5" × 1.2" area on the top layer. The control circuit fits in a 1.1" × 1.0" area on the bottom layer. The package style for the LTC3861EUHE is a 36-lead 5mm × 6mm QFN.

Resources

undefined

DC1822B - Schematic

undefined

DC1822B - Design Files

undefined

PDF

DC1822B Demo Manual

848.39 K

DC1822B

LTC3861 Demo Board | High Current, Dual Output Synchronous Buck Converter

LTspice 2

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.

To launch ready-to-run LTspice demonstration circuits for this part:

Step 1: Download and install LTspice on your computer.

Step 2: Click on the link in the section below to download a demonstration circuit.

Step 3: If LTspice does not automatically open after clicking the link below, 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.

Lt Spice

LTC3861 - Step-Down (Buck) Regulators, LTC7051 - Power Management

6.54 K

Lt Spice

LTC3861 Demo Circuit - High Current, Dual Output Synchronous Buck Converter with Inductor DCR Current Sensing (4-14V to 1.2V @ 25A & 1.8V @ 25A)

9.00K

LTpowerCAD 2

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.

To open the project file for this circuit:

Step 1: Download and install LTpowerCAD on your computer.

Step 2: Click on the link(s) in the section below to download part-specific project files.

Step 3: If the project file doesn't run, right-click the link and select "Save Target As." Then start the LTpowerCAD tool and open the project file by selecing "Open Project" from the "File" menu.

LTpowerCAD download and documentation