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ADC questions, thanks

Kailyn Chen
Genius 9560 points


Hi;

  If the input signal of ADC has the different GND with ADC, that is to say, the GND of ADC and the GND of input signal are not the same GND, does it have the effect of the ADC output? Or need the isolation? Please give me some advice. Thanks

Best regards

Kailyn

  • 0
    TI__Mastermind 29220 points

    Hi,

    in general, for signals that have to go from one device to another there are specifications for maximum output logic low voltage and minimum output logic high voltage for the chip driving the signal, and the chip receiving the signal will have an input maximum logic low specification and an input minimum logic high voltage spec.    If the ground potential is different then this may result in a shift of the levels of the signals out of one device relative to the other.  you would have to take into account the shift in logic levels when you look at the margin available in the logic levels from one device to the other.  if the chip driving a signal is shifted too high or too low then the signal might be outside the input requirements of the chip receiving.

    For signals that are AC coupled, such as the sample clock or the analog input of the ADC commonly are, then this is not a problem because the signal after the AC coupling is to be re-biased to the logic levels required by the receiving signal.    For differential signals like LVDS you would need to look at the range of common mode voltage the LVDS receiver is capable of receiving and consider that in light of the shift of ground potentials.

    Regards,

    RIchard P.