LTC3861

RECOMMENDED FOR NEW DESIGNS

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

Part Models: 4
1ku List Price: Starting From $3.46

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Part Details

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

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

Part Models: 4
1ku List Price: Starting From $3.46

Documentation

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)	Material Declaration Reliablity Data	Ultra Librarian SamacSys
LTC3861EUHE#TRPBF	36-Lead QFN (5mm x 6mm x 0.75mm w/ EP)	Material Declaration Reliablity Data	Ultra Librarian SamacSys
LTC3861IUHE#PBF	36-Lead QFN (5mm x 6mm x 0.75mm w/ EP)	Material Declaration Reliablity Data	Ultra Librarian SamacSys
LTC3861IUHE#TRPBF	36-Lead QFN (5mm x 6mm x 0.75mm w/ EP)	Material Declaration Reliablity Data	Ultra Librarian SamacSys

This is the most up-to-date revision of the Data Sheet.

Hardware Ecosystem

Parts	Product Life Cycle	Description
Digital Power System Managers 1
LTC2974	RECOMMENDED FOR NEW DESIGNS	4-Channel PMBus Power System Manager Featuring Accurate Output Current Measurement
Dual-Supply Monitors 1
LTC2960	RECOMMENDED FOR NEW DESIGNS	36V Nano-Current Two-Input Voltage Monitor
Multiple Output Buck Regulators 1
LTC3880	RECOMMENDED FOR NEW DESIGNS	Dual Output PolyPhase Step-Down DC/DC Controller with Digital Power System Management
Surge Stopper, Overvoltage, and Overcurrent Protection 1
LT4363	RECOMMENDED FOR NEW DESIGNS	High Voltage Surge Stopper with Current Limit

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

Tools & Simulations

LTspice 2

Models for the following parts are available in LTspice:

LTC3861
LTC3861-1

LTpowerCAD 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.

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.

Evaluation Kits

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

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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.

Product Details

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

DC1822B - Schematic
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DC1822B - Design Files
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DC1822B Demo Manual
848.39 K

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LTC3861

Part Details

Documentation

Data Sheet 1

Reliability Data 1

User Guide 1

Application Note 2

Design Note 1

Technical Articles 1

Analog Dialogue 1