Synchronous forward MOSFET driver needs no signal transformer

April 07, 2014 // By Graham Prophet
LT8311 is a high efficiency secondary-side MOSFET driver that operates without the need for primary control in an isolated synchronous forward converter.

The LT8311’s preactive mode eliminates the need for a signal transformer for primary to secondary-side communication by sensing signals on the secondary side to control synchronous rectification. This mode reduces component count and solution size.

The device operates over a 3.7V to 30V input voltage range and is used with a primary-side IC, such as the LT3752/-1. The complete forward converter can operate with input voltages ranging from 6.5V up to 400V+ making it ideal for a wide range of applications including hybrid/electric vehicle automotive requirements. It combines a 10 mA opto-driver and a feedback loop error amplifier to enable output voltage feedback from the secondary to the primary side. The entire system provides fixed frequency peak current mode control that has excellent line/load regulation and fast transient response. Additional features include a 1.5% reference voltage, a power-good monitor and programmable soft-start of the output voltage.

The IC comes in a TSSOP-20 package with several pins removed for high peak-voltage spacing, in E- and I-grade (-40°C to 125°C junction temperature), H grade (-40°C to 150°C) and MP grade (-55°C to 150°C), from $3.06 (1000).

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