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ADS7809 power supply sensitivity

Richard Schweizer
Prodigy 20 points
Other Parts Discussed in Thread: ADS7809

The 7809 is characterized for operations from 4.75V to 5.25V. The resulting power supply sensitivity (over temperature) is 8LSB (or 16LSB/V).

If the supply votage exceeds 5.25V (e.g. to a maximum of 5.35V), what is the effect? I.e are there effects other than just a proportional increase in error?

The inference I make is that it could add approximately (5.35V-5.25V)*16LSB/V=1.6LSB of error. Is this a valid inference?

  • 0
    TI__Guru* 95185 points

    Richard,

    Are you referring to the ADS7809? If so, reply back and I'll see that it gets to the proper person.

    Joseph Wu

  • 0
    TI__Expert 5705 points

    Hi Richard,

    From talking to our designer, most of the PSS is due to headroom limitations that become important when the supply voltage falls below the nominal 5V. In other words, the ADC output would probably show a larger offset when the supply goes below 5V than when it goes above. For this reason, we expect the ADC's sensitivity to a +0.35V vs. a +0.25V change in its supply voltage to be minimal. Although we cannot guarantee an upper limit, we think that your "linear" estimate may be conservative. I hope this helps.

    Best Regards,

    Harsha