Features

• High-Speed Top and Bottom Gate Drivers for
• 2-Switch Forward Converter
• On-Chip Rectifier and Self-Starting Architecture
• Eliminate Need for Separate Gate Drive Bias Supply
• Wide Input Voltage Supply Range: 18V to 80V
• Tolerant of 100V Input Voltage Transients
• Linear Regulator Controller for Fast Start-Up
• Precision UVLO with Adjustable Hysteresis
• Overcurrent Protection
• Volt-Second Limit Prevents Transformer Core Saturation
• Voltage Feedforward for Fast Transient Response
• Available in 16-Lead Narrow SSOP Package

Typical Application

Description

The LTC3705 is a controller for a 2-switch forward converter and includes on-chip bottom and top gate drivers that do not require external transformers. For secondary-side control, combine the LTC3705 with the LTC3706 PolyPhase® secondary-side synchronous forward controller to create a complete forward converter using a minimum of discrete parts. A proprietary scheme is used to multiplex gate drive signals across the isolation barrier through a tiny pulse transformer. The on-chip rectifier and the same pulse transformer provide gate drive bias power.

Alternatively, the LTC3705 can be used as a standalone voltage mode controller in a primary-side control architecture with optoisolator feedback. Voltage feedforward provides excellent line regulation and transient response.