LTC3855 - Dual, Multiphase Synchronous DC/DC Controller with Differential Remote Sense

Features

  • Dual, 180° Phased Controllers Reduce Required Input Capacitance and Power Supply Induced Noise
  • High Efficiency: Up to 95%
  • RSENSE or DCR Current Sensing
  • Programmable DCR Temperature Compensation
  • ±0.75% 0.6V Output Voltage Accuracy
  • Phase-Lockable Fixed Frequency 250kHz to 770kHz
  • True Remote Sensing Differential Amplifier
  • Dual N-Channel MOSFET Synchronous Drive
  • Wide VIN Range: 4.5V to 38V
  • VOUT Range: 0.6V to 12.5V without Differential Amplifier
  • VOUT Range: 0.6V to 3.3V with Differential Amplifier
  • Clock Input and Output for Up to 12-Phase Operation
  • Adjustable Soft-Start or VOUT Tracking
  • Foldback Output Current Limiting
  • Output Overvoltage Protection
  • 40-Pin (6mm × 6mm) QFN and 38-Lead FE Packages
Designed for Automotive and Transportation Applications
AEC-Q100 data available for specific packages


Typical Application

LTC3855 Typical Application
LTC3855 Typical Application

Description

The LTC3855 is a dual PolyPhase current mode synchronous step-down switching regulator controller that drives all N-channel power MOSFET stages. It includes a high speed differential remote sense amplifier. The maximum current sense voltage is programmable for either 30mV, 50mV or 75mV, allowing the use of either the inductor DCR or a discrete sense resistor as the sensing element.

The LTC3855 features a precision 0.6V reference and can produce output voltages up to 12.5V. A wide 4.5V to 38V input supply range encompasses most intermediate bus voltages and battery chemistries. Power loss and supply noise are minimized by operating the two controller output stages out of phase. Burst Mode operation, continuous or pulse-skipping modes are supported.

The LTC3855 can be configured for up to 12-phase operation, has DCR temperature compensation, two power good signals and two current limit set pins. The LTC3855 is available in low profile 40-pin 6mm × 6mm QFN and 38-lead exposed pad FE packages.

Packaging

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

Part Number Package Code Temp Package
Drawing
RoHS
LTC3855EFE#PBF TSSOP-38 FE E 05-08-1772 Yes
LTC3855EFE#TRPBF TSSOP-38 FE E 05-08-1772 Yes
LTC3855EUJ#PBF 6x6 QFN-40 UJ E 05-08-1728 Yes
LTC3855EUJ#TRPBF 6x6 QFN-40 UJ E 05-08-1728 Yes
LTC3855IFE#PBF TSSOP-38 FE I 05-08-1772 Yes
LTC3855IFE#TRPBF TSSOP-38 FE I 05-08-1772 Yes
LTC3855IUJ#PBF 6x6 QFN-40 UJ I 05-08-1728 Yes
LTC3855IUJ#TRPBF 6x6 QFN-40 UJ I 05-08-1728 Yes


LTC3855 Package Drawing
LTC3855 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
(1-99)
Price
(1k)*
RoHS
LTC3855EFE#PBF TSSOP-38 E $4.86 $3.40 Yes
LTC3855EFE#TRPBF TSSOP-38 E $3.46 Yes
LTC3855EUJ#PBF 6x6 QFN-40 E $4.54 $3.18 Yes
LTC3855EUJ#TRPBF 6x6 QFN-40 E $3.24 Yes
LTC3855IFE#PBF TSSOP-38 I $5.54 $3.88 Yes
LTC3855IFE#TRPBF TSSOP-38 I $3.94 Yes
LTC3855IUJ#PBF 6x6 QFN-40 I $5.13 $3.59 Yes
LTC3855IUJ#TRPBF 6x6 QFN-40 I $3.65 Yes
Buy NowRequest Samples
* 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
DC1441A LTC3855EUJ Demo Board | Dual Output, VIN = 4.5V to 14V, VOUT1 = 1.8V @ 17A, VOUT2 = 1.2V @ 17A $200.00
DC1586A LTC3855EUJ Demo Board | Dual Output, VIN = 4.5V to 25V, VOUT1 = 3.3V @ 5A, VOUT2 = 2.5V @ 5A $200.00
DC1617A-A LTC3855EFE Demo Board | Dual Output VIN = 4.5V to 26V, VOUT1 = 2.5V @ 15A, VOUT2 = 1.8V @ 15A $200.00
DC1617A-B LTC3855EFE Demo Board | Dual Output VIN = 13V to 36V, VOUT1 = 12V @ 6A, VOUT2 = 5V @ 10A $200.00
Buy Now
Click here to view our complete list of demo boards

Designed for Automotive and Transportation Applications

AEC-Q100 data is available for these specific part numbers. Please contact your local sales representative for more information regarding reliability reports or to inquire about parts that are not included. For more information, view our Automotive and Transportation page

Part Number Package Temp Price
(1-99)
Price
(1k)*
RoHS
LTC3855IFE#PBF TSSOP-38 I $5.54 $3.88 Yes
LTC3855IFE#TRPBF TSSOP-38 I $3.94 Yes
LTC3855IUJ#PBF 6x6 QFN-40 I $5.13 $3.59 Yes
LTC3855IUJ#TRPBF 6x6 QFN-40 I $3.65 Yes
Buy NowRequest Samples
* 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.

Applications

  • Computer Systems
  • Telecom Systems
  • Industrial and Medical Instruments
  • DC Power Distribution Systems

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Design Tools

LTspice

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

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
  • Step 2: Once LTspice is installed, click on the link(s) below to launch the simulation
  • Step 3: If LTspice 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:
LTC3855

LTpowerCAD

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:

Design tools for the following parts are available in LTpowerCAD:
LTC3855
LTC3855 Parallel

Technical Support