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TMUX1109: TMUX1109 single to dual supply mode switch

Arturo Morales
Prodigy 10 points
Part Number: TMUX1109

Hello, we are using a TMUX1109 to multiplex a couple of PMU's tied to DA and DB to bias/measure multiple pins on a DUT. We are mainly using the TMUX in single supply mode where we have VDD set to 4.8V from a system resource and then have VSS tied GND. However, we have a test instance where we dynamically adjust VSS down to -0.7V. We are running this at the edge of the allowable VDD-VSS allowed range. We are running into issues where we are damaging the TMUX as we transition from this single supply mode to our special dual supply where VSS has low resistance to VDD. My question is if the mode where we have VDD at 4.8V and VSS at -0.7V is allowed and what scenario do you see where we would damage VSS to VDD? A pulse where VSS pulls above GND?

  • 0
    Guru 279750 points

    The absolute maximum ratings would allow up to 6 V.

    Are there any voltage spikes when switching? Please check with an oscilloscope. (Normally, decoupling capacitors would prevent quick voltage changes.)

  • 0
    Prodigy 10 points

    Hi Clemens:

    Thanks for the note. When we switch from a relayed ground on VSS to a PMU to offset the voltage, we do see a spike on the oscilloscope but nothing that violates the 6 volt range. I read from other questions on the TMUX that asymmetrical dual supply is allowed, so 4.8V to -0.7V should not be an issue. Do you think the damage on VSS is due to a spike surpassing the absolute max of 6V or could a spike on VSS above GND could also present problems?

  • 0 in reply to Arturo Morales
    Guru 279750 points

    A positive spike on VSS can be a problem if it exceeds the absolute maximum ratings.

    It might also be possible that you have spikes when you (dis)connect the TMUX power.

  • 0
    TI__Genius 10552 points

    Hi Arturo,

    If you have VSS spikes above GND then you could potentially see device damage. Recommended operating conditions suggests it shouldn't surpass 0V and abs max showcasing no more than 0.3V. Are you getting spikes above 0V at all? If so, this is something that should be avoided to maintain proper operation of the device. 

    Regards,

    Alex