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TPS62143: Mechanical switch on EN causes failure

Lowell Stewart
Prodigy 50 points
Part Number: TPS62143
Other Parts Discussed in Thread: TPS62142,

I am having problem with the TPS62142 and the TPS62143 failing on a system when disabled/re-enabled.  We are using the recommended circuit, except the EN pin is connected to 12V and GND through a break-before-make mechanical switch.  Because of the nature of the project, I may not be able to repeat the test or get scope traces of the failure on the actual system any time soon.   I know that the switch connected to the EN pin is bouncing up and down for a few cycles at about 10-20uS period -- is that a problem?  If we don't hit the switch, there is no problem.   It has failed every time we disable and re-enable with the switch.  The switch itself is on the PCB about 5 inches away from the switchers on a skinny trace.  I am getting ready to try and reproduce the problem with one of the TI demo boards.

  • 0
    TI__Guru**** 191445 points

    Lowell,

    The TI EVM just uses a three pin header with a jumper to enable/disable.  I'm sure there is quite bit of "bounce" when making that connection.  I have never seen one fail because of EN bouncing.  ABS MAX voltage is VIN + 0.3 V, so it would not take much overshoot to cause damage, but once again, I have never seen chatter on EN cause an issue.  When I used to design for military projects, we were required to debounce all manual controls.  If you can get a waveform, it will help.

  • 0 in reply to JohnTucker
    Prodigy 50 points

    Thanks.   I now wish that I had debounced this manual control.   But I don't know if that is the problem or not.  I will try to figure out how to get access to more information about this failure.