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ADS7142: Input structure

Sal LaRussa
Genius 10040 points
Part Number: ADS7142


Hi,

we are looking to AC couple a signal to the input of the ADS7142.   Does the input structure of the ADS7142 require that the user uses external resistors to set the input bias appropriately? 

Also, we are running audio into the ADS7142.  There may be an ocassion where the user applys a 2V RMS audio input to the ADS7142 which will be powered from 1.8V.   Will we need to attenuate the signal to insure we never exceed AVdd or is there a mechanism internal to the ADS7142 to protect it from an overvoltage condition?

Thanks,

Sal

  • 0
    TI__Expert 5575 points
    Hi Sal

    ADS7142 input full scale range is 0 to AVDD. It is required to scale your input within this range to make sure device is not operated beyond recommended operating conditions.

    2VRMS would mean 2.82V peak voltage with 1.8V AVDD supply. ADS7142 has internal ESD diodes from input pin to AVDD. In case of overvoltage condition (input >= AVDD+0.3V typically) these diodes will conduct clamping input signal to AVDD. Excessive current through these diodes in OV condition can damage the device. Do you have any input series resistor between audio source and ADC input.

    It is not recommended to rely on internal ESD diodes in case of over voltage. We recommend to attenuate input signal to match ADC full scale range (0 to 1.8V in this case)

    Thanks & Regards
    Abhijeet