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UCC3895 - application

Hirotaka Matsumoto
Guru 27585 points
Other Parts Discussed in Thread: UCC3895

Hi all,

Would you mind if we ask UCC3895?

Please refer to following attachment file;
4744.UCC3895_Circuit.pdf

On this circuit(our customer's circuit), UCC3895 was broken by EOS which there was short between VCC(15pin) and GND(5pin), it hardly occurs so Xppm.
Compared with your recommendation circuit, there is much difference.
If you have some advice, could you let know us?
Inserting resistance between VDD  and  UCC3895 - 15pin is valid for?

We need your help.

Kind regards,

Hirotaka Matsumoto

  • 0
    Guru 27585 points

    Hi team,

    we guess that your days are so busy, however if you have some update, we appriciate you.

    So, could you let know us it?

    Kind regards,

    Hirotaka Matsumoto

  • 0 in reply to Hirotaka Matsumoto
    Guru 27585 points

    Hi team,

    We contributed it long time ago, but there is no reply.
    You don't any have comment, right?
    And then, when the UCC3895 was broken, FETs were broken also.

    Kind regards,

    Hirotaka Matsumoto

  • 0
    TI__Mastermind 25570 points

    Hello, Apologies for the delay in replying.

    First, if the UCC3895 breaks, then it is quite likely that the FETs will break too so I expect that the FETs dying is an effect of the UCC3895 dying and not a cause.

    Do the failures occurr immediately or after some warm-up time or after a long time in service

    This failure occurrs occasionally - Xppm - so it is likely due to a transient event fo some form.

    The classic transient events are ESD, Surge, turn-on and turn-off.

    I would look very closely at the voltage between VCC (pin 15) and gnd (pin 5) during start-up and turn off. There may be an overshoot on the regulator supplying the 13V Vcc rail.

    Inrush currents may also cause unexpectedly high voltage stresses between pins.

    I would also look very carefully at the PCB layout - especially the grounding arrangements to both pin 5 and pin 16 and their relation to the ground connection to the 13V regulator.

    Putting a low value resistor - typically 10R in series with the VC pin - will help filter out high frequency events - surge and ESD. Remember to keep the decoupling capacitors at the IC side of the resistor.

    Is it possible that the UCC3895 is getting too hot - it has a maximum junction temperature of 125C - although it should operate beyond that temperature its reliability and lifetime could reduce. The IC would only get to these dangerous temperatures if it were being heated by a nearby heat source.

    I hope this helps but please contact me if you can't identify the source of this problem.

    Regards
    Colin Gillmor

  • 0 in reply to Colin Gillmor
    Guru 27585 points

    Colin san,

    Thank you for your advice!
    We will use it as reference.

    Kind regards,

    Hirotaka Matsumoto