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TMUX7462F: Significant Leakage Current into Source Pin

David Bill
Prodigy 30 points
Part Number: TMUX7462F

Hello,

I integrated the TMUX7462F as protection from voltages above 4V according to the following draft into my system:

According to the datasheet, my expectation was that the switch SW should open, once Vsource exceeds 4V (3.3 V at VFP + 0.7 Vth). However, I noticed, that I need to apply more than 14 V at Vsource before the SW opens. At voltages between 4 and 14V, S1 is clipped to roughly 4V. In this region, a significant current is flowing through the 22 kOhm resistor into S1. This current reaches approx. 470 µA before the overvoltage detection triggers, which is way above any leakage current stated in the datasheet at room temperature. After revising the datasheet again, I noticed the internal diode between D1 and VFP, which might sink current into VFP until it's breakthrough is reached (obviously around 470 µA). Then, any voltage increase at Vsource also increases the voltage at S1, thus triggering the overvoltage status.


Can you confirm, that this behaviour is correct and I don't have a damaged chip? Further, is there any section in the datasheet that I missed or is my assumption correct, that the diode is causing this "issue"?

For my application, I need the voltage at S1 (below the 22 kOhm resistor) to be as high as the Vsource. Is there any possibility to do this with this setup?

Thanks for your support!

Best regards,

David

  • +1
    TI__Genius 10552 points

    Hi David,

    It does sound like what you described is the occurring here - the diode is likely sinking current. Would it be possible to size down the 22K resistor here to reduce the current drop?

    Thanks!

    Alex

  • 0 in reply to Alex Vish
    Prodigy 30 points

    Hi Alex,

    thanks for your fast response!

    In my application I want to connect the voltage below the 22 kOhm (at S1) as load to a sensor element. The resistor is needed to limit current. I can decrease it's value, however this comes with increased load current, so I don't have full freedom in voltage-current choice anymore.

    Thanks anyway for confirming my assumption.

    Regards,

    David