Features

• Wide Input Supply Range: 3.7V to 30V
• Preactive Mode:
• No Pulse Transformer Required
• DCM Operation at Light Load
• SYNC Mode:
• FCM or DCM Operation at Light Load
• Achieves Highest Efficiency
• 1.5% Feedback Voltage Reference
• 10mA Opto-Coupler Driver
• Output Power Good Indicator
• Integrated Soft-Start Function

Typical Application

Description

The LT®8311 is used on the secondary side of a forward converter to provide synchronous MOSFET control and output voltage feedback through an opto-coupler. The LT8311’s unique preactive mode allows control of the secondary-side MOSFETs without requiring a traditional pulse transformer for primary- to secondary-side communication. In preactive mode, the output inductor current operates in discontinuous conduction mode (DCM) at light load. If forced continuous mode (FCM) operation is desired at light load, the LT8311 can, alternatively, be used in SYNC mode, where a pulse transformer is required to send synchronous control signals from the primary-side IC to the LT8311.

The LT8311 offers a full featured opto-coupler controller, incorporating a 1.5% reference, a transconductance error amplifier and a 10mA opto-driver. Power good monitoring and output soft-start/overshoot control are also included. The LT8311 is available in a 16-lead FE package with pins removed for high voltage spacing requirements.