LT3781

PRODUCTION

Bootstrap Start Dual Transistor Synchronous Forward Controller

Part Models: 4
1ku List Price: Starting From $6.55

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Overview

High Voltage Operation up to 72V
Synchronizable Operating Frequency and Output Switch Phase for Multiple Controller Systems
Synchronous Switch Output
Undervoltage Lockout Protection with 6V Hysteresis for Self-Biased Power
Fixed Frequency Operation to 350kHz
Local ±1% Voltage Reference
Input Overvoltage Protection
Low Start-Up Current
Programmable Start Inhibit for Power Supply Sequencing and Protection
Optocoupler Support
Soft-Start Control

The LT3781 controller simplifies the design of high power synchronous dual transistor forward DC/DC converters. The part employs fixed frequency current mode control and supports both isolated and nonisolated topologies. The IC drives external N-channel power MOSFETs and operates with input voltages up to 72V.

The LT3781 is ideal for output derived power schemes, through the use of a large undervoltage lockout hysteresis range. The part is also equipped with an 18V V_CC shunt regulator, which prevents exceeding absolute maximum ratings while in trickle start applications.

The LT3781’s operating frequency is programmable and can be synchronized up to 350kHz. Switch phase is also controlled during synchronized operation to accommodate multiple-converter systems. Internal logic guarantees 50% maximum duty cycle operation to prevent transformer saturation.

The LT3781 is available in a 20-lead SSOP package.

Applications

Isolated Telecommunication Systems
Personal Computers and Peripherals
Distributed Power Step-Down Converters
Lead Acid Battery Backup Systems
Automotive and Heavy Equipment

Part Models: 4
1ku List Price: Starting From $6.55

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
LT3781EG#PBF	20-Lead SSOP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3781EG#TRPBF	20-Lead SSOP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3781IG#PBF	20-Lead SSOP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3781IG#TRPBF	20-Lead SSOP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys

Part Models	Product Lifecycle	PCN

Aug 6, 2022 - 22_0171 Laser Top Mark Conversion for SSOP Packages Assembled in PNG
		PCN22_0171_Form Material_Report Delta Qualification Matrix
LT3781EG#PBF	PRODUCTION
LT3781EG#TRPBF	PRODUCTION
LT3781IG#PBF	PRODUCTION
LT3781IG#TRPBF	PRODUCTION

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

Software Resources

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Tools & Simulations

LTspice

Models for the following parts are available in LTspice:

LT3781

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.

Evaluation Kits

LT3781EG, LTC1698EGN, LT1783CS5 | Isolated Synchronous, Forward Converter, VIN=36V-72V, VOUT=3.3V @ 15A

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Product Details

DC479A Demo Board for:
LT1783 1.25MHz, Over-The-Top Micropower, Rail-to-Rail Input and Output Op Amp in SOT-23
LTC1698 Isolated Secondary Synchronous Rectifier Controller
LT3781 Bootstrap Start Dual Transistor Synchronous Forward Controller