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Input impedence of PCM2902 in off state?

Norman Chu
Prodigy 10 points
Other Parts Discussed in Thread: PCM2902

I've been looking at the PCM2902 ( http://focus.ti.com/lit/ds/symlink/pcm2902.pdf ) ADC and I'm wondering what the input impedence of the chip is in the off state? I'm concerned that if powered down, the chip may load down whatever circuit is connected to the input.

The input impedence is listed as 30kOhm, but since there isn't any information on how the ADC is designed, do any TI designers/engineers know whether the input impedence will rise or fall?

  • 0
    TI__Expert 4625 points

    Hi Norman,

    When the chip is powered down, the inputs will go to a high impedance state (I measured >10Mohm on our eval board), and thus, will not load down any other connected circuitry.

    I also verified that the 30kohm input impedance is accurate.  I measured ~33kohm in the lab.

    Regards,

    Nick