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TMUX7411F: Bridging a current loop

Theo Keinarth
Prodigy 160 points
Part Number: TMUX7411F

Tool/software:

Hi TI-Team

I nee to bridge a 4-20mA current loop analog frontend under fault conditions. Under normal conditions VD and VSS present the MUX has nearly no impact on the current loop which is awesome. But if the MUX has no supply I'm not so sure about the values in the Datasheet. Under 7.9 Fault Conditions its says +/-125uA with VD = VSS = 0V on the Sx pins but on the Dx pins its +/-90nA. To my Understanding the Sx pins are OVP and the Dx pins are not. Why is there so much current going through the protected Sx pins?

Can I use this MUX to bridge my current loop frontends?

Thank you in advance!

Regards Theo

  • +1
    TI__Genius 13690 points

    Hello Theo

    When the fault event occurs the path from s to d is cutoff and most of the leakage you see from s pin will be mostly going  to ground.

    The s pin contains ovp circuitry that could consuming the +/-125uA current.

    Other than that the device is fine your application.

    Please let me know if you need any further assitance!

    regards,

    Kameron

  • 0 in reply to Kameron Hill
    Prodigy 160 points

    Hi Kameron

    The main issue is there are more current acquisition systems in one loop in our application. So if I would short the loop with 125uA to GND my circuit would alter the current in the loop for all other systems. As long as Supply is present on the MUX only an OVP event would cause this issue which would be OK. But if my supply dies i would need to supply the MUX ICs from somewhere else which is impossible for my application.

    Thanks for your Help.

    Regards Theo