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ADS1226: What happens on startup?

nadine lhermet
Prodigy 20 points
Other Parts Discussed in Thread: ADS1226

Hi,

I'm wondering what happens on startup with ADS1226?

ADS1226 has a different comportement when it startups with Vref with no potential, and when it startups with Vref potential no null.

When ADS1226 startups with Vref connected to a potential, all seem to be ok, datas are valid;

But when ADS1226 startups with Vref not connected to any potential, datas measures are negative voltage, and if Vref is connected to a potential, dats measures are always negative voltage.

Could you help me?

Thanks,

  • 0
    TI__Guru** 113765 points

    Hi Nadine,

    Welcome to the forum! The ADS1226 requires a voltage reference.  The output result depends on a valid reference.  Any result without a reference applied is meaningless, and could be most any value.  If you apply an offset calibration before you connect the reference, you will see an error.  After the reference is applied you should run an offset calibration in any case.

    Best regards,

    Bob B

     

  • 0 in reply to Bob Benjamin
    Prodigy 20 points

    Hi,

    I understand that ADS1226 should have a valid reference to give valid conversion.

    But what I don't understand is that ADS1226 doesn't react identacally when it starts with a valid reference and when it starts without reference;

    When ADS1226 is power on with valid reference, data read are valid, if reference is disconnect, data read are meaningless, if I connect reference to a valid potential, data read are valid; that's well,

    But when ADS1226 is power on without valid reference, data read are meaningless, and if I connect reference to a valid potential, data read are negative.

    Best Regards,

    N.B.

  • 0 in reply to nadine lhermet
    TI__Guru** 113765 points

    Nadine,

    On power up the ADC issues a calibration.  If the calibration is based on a meaningless reference, all data taken after the reference is applied will be meaningless.  Issuing a calibration once the reference is applied should correct the output results.

    In the case where the reference is valid on power up, the calibration information will be correct as stored within the ADS1226.  As you power off and on the reference, the calibration information will be retained unless you issue the calibration with the reference turned off.

    Best regards,

    Bob B