2-Switch Forward Controller and Gate Driver

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.

Applications

* Isolated 48V Telecommunication Systems

* Internet Servers and Routers

* Distributed Power Step-Down Converters

* Automotive and Heavy Equipment

* 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