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TSC2046: TSC2046 internal reference loading

kvdv
Prodigy 90 points
Part Number: TSC2046

Would it be possible to add a minor external load on the internal (buffered) reference?

I would like to add a external 10k or 100k NTC temperature sensor on the aux input via 10k or 100k to Vref.

Thanks.

  • 0
    TI__Mastermind 20085 points
    Hi Kvdv

    Could you please provide me more details about your application? and What do you mean with "aux input via 10k or 100k to Vref"?

    Best Regards
    Jose Luis Figueroa
    Application Engineer
  • 0 in reply to José Luis
    Prodigy 90 points

    Hi Jose,

    Thanks for your reply.

    I would like the temperature measurement to be ratiometric. Since the TSC2046 uses single ended conversions on the aux input with Vref as referene to the ADC I thought connecting the NTC as shown below:

    I can't find if external loading of Vref is allowed in the datasheet.

  • 0 in reply to kvdv
    TI__Mastermind 20085 points
    Hi Kvdv

    Sorry for the delay. I am a little confused, are you using single-ended or differential reference?

    Best Regards
    José Luis Figueroa
    Application Engineer
  • 0 in reply to José Luis
    Prodigy 90 points

    Hi Jose,


    Happy new year!

    I think the auxiliary, internal temperature and battery input channels can only be measured using single ended conversions.
    It appears that Vref is always used as the reference for the ADC when singled ended conversions are done. If Vcc could be selected as the reference for single-ended conversion I could simply connect the NTC circuit to Vcc. Since this seems impossible I would like to connect the NTC to Vref so it's ratiometric.

    For the "normal" touchscreen channels I use the differential mode with Vcc as reference.

    Thanks



  • 0 in reply to kvdv
    TI__Mastermind 20085 points
    Hi Kvdv

    If you use that circuit, I think that it shouldn't generate any issue.

    Best Regards
    Jose Luis Figueroa
    Application Engineer