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TPS2042: TPS2042 power on Vout when switch is disabled

M Leeters
Prodigy 20 points
Part Number: TPS2042

Tool/software:

Dear,

We have some TPS2042 which fail after a while we think there are two type of fails:

1. We use one USB in OTG mode which is connected to a TPS2042 output.

What could happen is that the enable pin of the TPS2042 is HIGH (so output disabled) but there is still +5V on the output pin.

I can't really find in the datasheet if this is allowed so it could be expected that this breaks the TPS2042.

This only could happen when we are developing and not in the real product.

2. We have seen now on 2 board (of the 30 pieces which we have produced now) that the output isn't enabled when the enable pin is pulled LOW.

There hasn't been any load on the +5V (and also no other +5V applied to it). Except an LED and a 18k resistor for faster depletion of the output capacitor.

See the part of the schematic for the output:

And the input part:

  • 0
    TI__Mastermind 31860 points

    Hi,

    TI US is out for Labor Day, we will be back on 9/2.

    Regards

  • 0 in reply to Tommy Lin
    Prodigy 20 points

    Hi, Did you have time to look at the issue?

  • 0 in reply to M Leeters
    TI__Mastermind 32751 points

    Hi M. Leeters.

    1.  This is a single fet power switch that is configured to block the input voltage from connecting to the output voltage.  If you drive 5V on the output pin, the body diode of the FET switch will conduct current and present a voltage on the input if the voltage on the output is higher than the input.  If you need voltage to be blocked in both directions, then you need a power switch that has to FETS that configure the body diodes so that no current can flow.

    2.  If the switch is not turning on, then it is likely that the switch has been damaged, this can occur because of the first condition that you listed in your system.

    I cannot review your schematic because it is not complete.  I cannot see the circuitry on the input side of the switch and how the other switch is configured.

    Can you provide the full schematic?

    Regards,

    Chuck

  • 0 in reply to Chuck Branch
    TI__Expert 3920 points

    Hi Chuck,

    I was just in contact with Mr. Leeters via mail on this issue and will  take this conversation offline to share schematic.

    Thanks!
    Best Regards,
    Brian

  • 0 in reply to Brian Zoro
    TI__Mastermind 32751 points

    Brian,

    I am going to close the E2E thread because we have move discussion to email to protect customer schematic. 

    Regards,

    Chuck