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LM5025A / to detect shutdown

K.Yaita
Guru 29720 points
Other Parts Discussed in Thread: LM5025A

Hi Team,

My customer would like to detect the shutdown timing of LM5025A.
Is there any pin that can be confirmed shutdown by UVLO or CS2 hiccup current limiting mode?

I thought it could be possible to observe SS pin, however it seems to take quite time to become "Low" after the shutdown.
In other words, how much of the time from shutdown to SS pin is "Low"? Is it possible to shorten this time?

I would also like to know if there is another way to detect shutdown.

Your help would be really appreciated.

Best Regards,
Yaita

  • 0
    TI__Expert 5900 points
    Hi Yaita,
    I agree with you that SS could be monitored for the uvlo or current limit detection.
    however there is a MOS to drive SS to low when shutdown occur. The discharging time should be very short compared with the charging time.
    You can capture the ss directly to see the time.

    Br
  • 0 in reply to Kening Gao
    Guru 29720 points

    Hi Kening-san,

    I am asked additional question from my customer.
    Which of the signal OUT_A or OUT_B outputs at the end when the shutdown as the following occures?
    *My customer adopts N-Channel Active Clamp.

    1) Shutdown caused by UVLO
    2) Shutdown caused by SS to be "Low"
    3) Shutdown caused by decreasing VCC
    4) Shutdown caused by CS2 hiccup current limiting mode

    Does it all depend on the shutdown timing?
    Your support would be appreciated.

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Intellectual 1390 points

    Hi Yaita-san,

    Please refer to below description in the datasheet, I believe both OUTA and OUTB should be disabled for all the above 4 conditions 

    "In the event of a fault as determined by VCC undervoltage, line undervoltage (UVLO) or second level current limit, the output gate drivers are disabled and the softstart capacitor is fully discharged."

    Could you kindly let know if the real sillicon's behavior is different from datasheet.

     

    Thanks

    Frank  

  • 0 in reply to Frank TANG
    Guru 29720 points

    Hi Frank-san,

    Yes, I agree with you about the following too.
    >I believe both OUTA and OUTB should be disabled for all the above 4 conditions

    My customer would like to know which outputs at the end when shutdown occures.
    *I would like to know which is the correct waveform 1) or 2) when shutdown occures.


    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Intellectual 1390 points

    Hi KENSUKE, YAITA

    I think it is possible for either case. It only depends on what time the fault signal arrives

     

    Regards

    Frank