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UCC25630-1EVM-291: questions on EVM schematic & passive components

Leo Chow
Expert 3120 points
Part Number: UCC25630-1EVM-291

Hi,

I have a question with regards to UCC25630-1EVM-291, I can't seem to understand the exact function of D10 and R21 components on schematic. Will product team be able to advise on this? 

Regards,
Leo

  • 0
    TI__Mastermind 26215 points

    Hi Leo,

    D10 and R21 are to help avoid opto-coupler saturation which causes a delay in the opto-coupler response and results in a delay in the transient response. Normally the FB pin voltage is loosely regulated to ~5.5V and the device will measure the amount of current that is pulled out of the FB pin as the feedback signal. If the opto-coupler starts to saturate and the voltage on the FB pin begins to drop, D10 turns on and sources additional current to the FB pin to try to prevent the opto from fully saturating. R21 sets how much additional current is sourced to the opto-coupler while D10 is conducting.

    Best Regards,

    Ben Lough