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Original question:

TLA2024: Open channel conversion result

TLA2024: How can it control the ADC results when all the inputs are enabled, but open/floating?

Yoshikazu Kawasaki
Intellectual 515 points
Part Number: TLA2024

Hello,

My question is related to the one posted previously by cafain-san, but my customer would like to have 0V output results when all the inputs are enabled, but open/floating.  They'd like to make the condition to have 0V outputs to think about the case where the input is disconnected unexpectedly like the connector to the ADC so that they can detect such unusual case.  Would you please tell me how they should do for the inputs?  Should they add pull down resistors?  The datasheet says the FSR needs to be +/-0.256V(min), so I'm not sure how they should do.  Note that it doesn't have to be 0V, but a certain voltage will work well if it is stable when the inputs are open, but 0V should be the most stable condition.

Best Regards,

Yoshikazu Kawasaki

  • 0
    TI__Mastermind 31655 points

    Hello Kawasaki-san,

    Yes, a pulldown resistor or a pullup resistor would be an acceptable solution. The main concern is in not turning on the ESD protection diodes, so the absolute voltage on any of the inputs should fall within the range described in equation 1 in the datasheet: GND – 0.3 V < V(AINX) < VDD + 0.3 V.

    Regards,

  • 0 in reply to Scott Cummins
    Intellectual 515 points

    Hello Scott-san,

    Thank you very much for your quick reply.  I understand the input voltages after adding pull down/up resistors need to be within the range of GND – 0.3 V < V(AINX) < VDD + 0.3 V to protect from the ESD event.  Otherwise the ESD protection will not work.

    Best Regards,

    Yoshikazu Kawasaki