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ADS124S08: Available VREF current at AVDD = 3.3V?

Glenn Monroe
Intellectual 330 points

Part Number: ADS124S08

The spec for the ADS124S08 says that VREF can supply -5 to 5mA for AVDD = 2.7 - 3.3V and -10 to 10mA for AVDD = 3.3V - 5.25V.  I am using 3.3V for AVDD.  This will VREF will be powering a set of strain gauges that use about 6mA.  I am assuming that the cutoff between 5mA and 10mA is not abrupt at 3.3V.  What can I expect when I see some ripple across my power supply that takes it to either side of 3.3V?

  • 0
    TI__Guru** 113765 points

    Hi Glenn,

    The reference was designed more to bias sensors as opposed to powering sensors.  Generally we recommend using another source, and I had recommended using the analog supply to one of your colleagues in the past.  But apparently this was too noisy in the application.

    Part of the problem here is having enough supply overhead to be able to deliver the current and hold the reference at the rated voltage over temperature.  You should not see an abrupt change in current at 3.3V, especially if the measurement is ratiometric.  If the reference voltage droops slightly due to an increase in current at a lower voltage, it should not effect the conversion result for a ratiometric measurement as the drift would cancel.

    As to the reference voltage itself, you should be relatively stable unless the analog supply goes below 2.7V.  Slightly above and below 3.3V should not have an impact.

    Best regards,

    Bob B