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UCC28251: UCC28251 EVM 501 question

Red Yen
Expert 4360 points
Part Number: UCC28251

Hi team,

 

My customer is looking for UCC28251 for drone application

They are reference EVM-501 now, one question regarding to following red circle, What is function for this?

 


  • 0
    TI__Mastermind 31580 points
    Hi Red,

    I think its a form soft start circuit. At start-up the cap C47 is discharged, 0V, so Q11(?) is on. As C47 charges towards Vdd2 through 1M the voltage on the emitter will follow the base, voltage follower circuit. Q11 controls the voltage on the anode of the opto-diode and provides a controlled ramp of the voltage and current in the opto diode.

    Regards

    Peter