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TPS54325: About the PowerGood Signal

keisuke
Intellectual 475 points
Part Number: TPS54325

Hi team,

I have a question about the ramp up of the PowerGood Signal in the TPS54325.

I designed a power circuit which the power good signal pulls up the VREG5 pin(#3) throught a 10k resistor.

When I measured start up waveform, I confrimed the glitch in the Powergood signal(ch4).

Could you tell me about the cause of the glitch?

Does this problem hardly affect?

Best Regards,

keisuke

  • 0
    TI__Expert 8245 points

    Hi,

    Please use a 20k - 150k resistor as datasheet recommended and try again. The power-good function is activated after soft start has finished, there might be some external noises on Pgood before start-up.Thanks.

  • 0 in reply to Iven Su
    Intellectual 475 points

    Dear lven

    Thank you for your reply.

    I remeasured a waveform of Powergood signal after a pull up resistor change to 100kohm.

    But the glitch is still appear.

    Best Regards,

    keisuke

  • 0 in reply to keisuke
    TI__Expert 8245 points

    Hi,

    It looks like the glitch is coupled by a current path, could you please also probe Vin/Vout current? And what's the value of VREG5 capacitor? If possible, could you please attach its schematic and layout? We will also check the issue on TPS54325EVM, thanks.

  • 0 in reply to Iven Su
    Intellectual 475 points

    Hi Iven

    I measured the Vin/Vout current waveform.

    Those waveform were normal.

    I couldn't find the glitch in current waveforms. I haven't the TPS54325EVM,

    so could you please check if the PowerGood signal has the glitch?

    Best Regards,

    keisuke

  • 0 in reply to keisuke
    TI__Expert 8245 points

    Hi,

    Could you please attach your components values and what's your input and output voltage/load? Thanks.

  • 0 in reply to Iven Su
    Intellectual 475 points

    Hi Iven

    Thank you for your adivce.

    I describe some componets values of TPS54325 circuit.

     - Vin : 12V

     - Vout : 1.2V

     - Io : 1A(max)

     - Cin : GRM21BR61E226ME44L (22uF/25V) x 3pcs ,

                GRM033R6YA104KE14D (100nF/35V) x 1pcs

     - Cout : GRM21BR61E226ME44L (22uF/25V) x 2pcs

     - L : SPM6530T-1R5M100 ( 1.5uH)

     - VREG5 pin : GRM188R61H225KE11D (2.2uF/50V)

    Best Regards,

    keisuke 

  • 0 in reply to keisuke
    TI__Expert 8245 points

    Hi,

    How do you do your start-up, by Vin or Enable? Thanks.