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UCC2895: Shut down when at Ta=70°C

john Ma
Intellectual 280 points
Part Number: UCC2895

Hi，

Recently, during I debug UCC2895, the power system is OK at 25°C and -40°C, however, once the temperature is 70°C, output voltage begin to drop slowly form normal value. Then I mornitor the voltage of SS/DISB port, is drops from 5V to below 2.4V slowly, at that moment output voltage disappears. When temperature returns to normal, everything is OK. My condition is : RT=110kohm(IRT=27uA), FOSC=100KHz, VDD=12V.

I will appreciate for your reply, thanks very much.

  • 0
    TI__Mastermind 25570 points
    Hello John

    The voltage at the SS/DISB pin can drop if the internal RS flip flop trips and the current sink at the pin turns on. This can happen if the over current comparator trips. If the over current protection of the device becomes active then I would also expect the output voltage to drop.
    The first thing I would suggest is that you take a look at the amplitude of the signal at the CS pin. 2V is the current limit point. Check also if the current sensor has a significant temperature co-efficient which might send the controller into current limit at higher temperatures.

    It may be worthwhile to change the controller - just in case it has become damaged in any way.

    Please let me know how you get on

    Regards
    Colin
  • 0 in reply to Colin Gillmor
    TI__Mastermind 25570 points

    Hi John

    Since you haven't updated this thread I'll assume that you have resolved the issue.

    Regards

    Colin