LTC3870 - PolyPhase Step-Down Slave Controller for Digital Power System Management


  • LTC3880 Family Phase Extender Supporting LTC3880/3880-1, LTC3883/3883-1, LTC3886, LTC3887 Master Controllers
  • Cascade with Multiple Chips for Very Large Current Applications
  • Accurate PolyPhase Current Sharing
  • EXTVCC Capable of 5V to 14V Input
  • Wide VIN Range: 4.5V to 60V
  • Wide Output Voltage Range : 0.5V to 14V
  • Wide SYNC Frequency Range: 100kHz to 1MHz
  • Pin Programmable of CCM/DCM Operation
  • Pin Programmable of Phase-Shift Control
  • Integrated Powerful N-Channel MOSFET Gate Drivers
  • Available in a 28-Pin (4mm × 5mm) QFN Package

Typical Application

LTC3870 Typical Application
LTC3870 Typical Application


The LTC®3870 is a PolyPhase® step-down slave controller specially designed for multiphase operation with the LTC3880 family digital power system management DC/DC controllers. It provides a small and cost effective solution for supplying very large currents by cascading it with a master controller. A peak current mode architecture provides the LTC3870 with excellent current sharing from phase to phase and from chip to chip.

Coherently working with the LTC3880 family, the LTC3870 does not require additional I2C addresses, and it supports all programmable features as well as fault protection. The constant switching frequency can be synchronized to an external clock from the master controller from 100kHz to 1MHz.

  Onboard MOSFET Gate Drivers Package
LTC3870 Yes 4x5 QFN-28
LTC3870-1 No – Works with DrMOS and Power Blocks 4x4 QFN-24


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
LTC3870EUFD#PBF 4x5 QFN-28 UFD E 05-08-1712 Yes
LTC3870EUFD#TRPBF 4x5 QFN-28 UFD E 05-08-1712 Yes
LTC3870IUFD#PBF 4x5 QFN-28 UFD I 05-08-1712 Yes
LTC3870IUFD#TRPBF 4x5 QFN-28 UFD I 05-08-1712 Yes

LTC3870 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
LTC3870EUFD#PBF 4x5 QFN-28 E $3.36 $2.35 Yes
LTC3870EUFD#TRPBF 4x5 QFN-28 E $2.41 Yes
LTC3870IUFD#PBF 4x5 QFN-28 I $3.62 $2.53 Yes
LTC3870IUFD#TRPBF 4x5 QFN-28 I $2.59 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
DC2089A-A LTC3880EUJ/LTC3870EUFD RSENSE Demo Board | 7V ≤ VIN ≤ 14V; VOUT = 0.8V to 1.8V @ 80A Contact Factory
DC2089A-B LTC3880EUJ/LTC3870EUFD DCR SENSE Demo Board | 7V ≤ VIN ≤ 14V; VOUT = 0.8V to 1.8V @ 80A $275.00
DC2155A-B LTC3886UKG/LTC3870UFD Demo Board (RSENSE) | 4 Phase Single Output PMBus Buck 18V≤VIN ≤54V, VOUT=12V at 48A, 150kHz Contact Factory
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Companion Boards

Part Number Description Price Documentation
DC1613A USB-to-PMBus Controller for Use with LTpowerPlay $50.00
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Click here to view our complete list of demo boards


  • High Power Distributed Power Systems
  • Telecom Systems
  • Industrial Applications

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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

Models for the following parts are available in LTspice:


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

To open the project file for this circuit:

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