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ADS1248 Burnout Current Source Accuracy Changed?

Mike N
Prodigy 90 points
Other Parts Discussed in Thread: ADS1248

Hello.

We are using ADS1248 in a resistive strain gauge application and have done so for several years.  We understand the burnout current sources are not terribly stable and would introduce errors into the measurement if left on with the main IDAC sources.  This is discussed in the latest data sheets but is not in older data sheets.  As the original design was done using older data sheets, the burnout current sources were left on (+/- 0.5uA into 2mA IDACs).  We did not notice any errors until recently, when small temperature related drift was noted.  Once the burnout sources were turned off the error was removed.

Has there been a change in the burnout current sources, specifically a degradation in temperature stability, since initial release of the ADS1248 which might explain our observations?

  • 0
    TI__Guru** 113765 points

    Hi Mike,

    As you have stated, the ADS1248 has been around for quite some time and there have not been any recent changes to the silicon.  As you also mentioned we did do a more recent update to the datasheet expanding a lot of information based on questions we get.  One of the more common questions does happen to be related to using burn-out current sources (BCS) all the time, and we suggest not doing that as it will cause error.  The error will increase with any component that can drift in the circuit path, such as filter resistors.

    I am not aware of any issues with the BCS.  However, the BCS are not precision current sources and will have variation based on process variation and will be prone to temperature drift.  These BCS sources by design are much different than the IDAC current sources and were never meant to be used all the time.  For example, even small additional currents can cause heating in sensors such as thermocouples.

    Best regards,

    Bob B