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LM5021-Q1: I am just testing the control circuit without primary line power or load. I am applying voltage at the VIN pin and the overload circuit is not working as described in the data sheet.

Ernest Wittenbreder
Prodigy 10 points
Part Number: LM5021-Q1

When I apply voltage to VIN I get the chip starting up at the ~20 volt threshold, but if I lower the voltage below 20 volts the chip stops.  It goes through the overload cycle a few times and then it appears to disable the VCC supply and operation stops.  I can get operation to start again if I push the VIN voltage above 20 volts.  This does not appear to be consistent with the data sheet, or am I missing something?

  • 0
    TI__Expert 7395 points

    Mr. Technical Witts,

    I agree with you that this should not happen beacause of Vin hysteresis. It should shutdown until 7-8 v. (Then again we recommend 23v as max full start across process and temperature so be sure to power it above 23v initially. )

    Have you seen this on 1 device or mulitiple?

    To get an idea what is going on could you provide signals of Out, SS, Vin, and comp?

    Regards

    John