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TPS23753A: Secondary Soft Start and CTL pin Voltage

Michael Jeong1
Expert 2630 points
Part Number: TPS23753A

Hello Expert,

I have some question.

1. I have a question about resistor and capacitor value Secondard Soft Start which is based on user guide "TPS23753AEVM-001 Evaluation Module for TPS23753A (Rev. A)".

    If input voltage has momentarily DIP situation, the soft start function does not work.

    At this situation, do you have some guide and solution?

   ex, R13, C14 are able to chaneg from xxx to xxx. or Add circuit or New reference schematic.

   

2. If resistor 2kohm is add to between 3pin and 4pin of U1, Is it ok? or is there any problem?

    If I do it, 2.5V will be supplied to CTL pin of TPS23753A.

    What's the voltage range for CTL pin input of TPS23753A?

Best regards,

Michael

  • 0
    TI__Mastermind 21320 points

    Hello Michael, 

    1. The secondary side soft start circuit helps control the ramp rate of the output voltage. A larger capacitor will slow down the turn on time, resulting in a smoother transition . A smaller capacitor will have a faster turn on, but can cause an overshoot of the output voltage. Typical range here is 1uF - 10uF. 

    Adjusting the resistor can have the same affect, but we normally adjust capacitor. 

    2. This will affect the compensation, and I am not sure if it is a better course than simply optimizing the current feedback. The CTL pin recommended voltage is to stay below Vb, which should be ~5V. 

    If this post answers your question, please indicate so by marking this thread as resolved. Thank you.

     

    Regards, 

     

    Michael P.

    Applications Engineer

    Texas Instruments