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ISO5452: Question for ISO5452 DESAT pin behavior

Jacky Wang(QD)
Genius 10800 points
Part Number: ISO5452

Hi Team,

Our customer is evaluating the ISO5452 in their application, during their test, they found that when there is no HV voltage applied on the IGBTs, we will still see the FLT triggered to low. They want to know if this is the normal behavior for our device?

Thanks.

  • 0
    TI__Genius 13650 points

    Hi Jacky,

    This is not normal behavior of the ISO5452. The FLT signal should only go low when the driver detects that the voltage on the DESAT pin on the high side has exceeded the 9V threshold for longer than the glitch filter (330ns).

    • When the FLT signal goes low is the customer just switching the IGBT ON and OFF with no power applied?
      • When you mean that no power is applied is the input to the IGBT set to 0V or is it left floating?
    • Are all the components in the schematic connected to the DESAT pin populated on the board?
    • Could the customer probe the DESAT pin to see the voltage on that pin at the same time that the FLT signal goes low to verify the voltage level on DESAT?

    Best regards,

    Andy Robles

  • 0 in reply to Andy Robles
    TI__Genius 10800 points

    Hi Andy,

    Thanks for the feedback, we will double check these items with customer and feedback to you soon.

  • 0 in reply to Jacky Wang(QD)
    TI__Genius 10652 points

    Jacky,

    Please also check VCE of IGBT when OUTH high.

    I am wondering if the low charge current of DESAT system can't forward bias the IGBTs PN junction, or some nuance of IGBT with zero collector current.

    In the past i had done testing with IGBTs, without HV applied and the DESAT charge current still passed to ground and did not trigger FLT. I am unsure why their testing would be different.

    Best

    Dimitri