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ADS42LB69: About ADS42LB69 VCM

user6481287
Expert 1200 points

Part Number: ADS42LB69

The VCM of ADS42LB69 in the reference schematic diagram of AD did not receive the AD input, so I did not receive the AD input either. The AD used in the past was VCM and was connected to the AD input, so I don't know if there is any problem.

  • 0
    TI__Guru* 91947 points

    User,

    If using AC coupling like the reference design, you do not need to use the VCM output.  The input common-mode is set internally using a 5-kΩ resistor from each input pin to VCM so the input signal can be ac-coupled to the pins. The ac-coupling capacitors allow the analog inputs to self-bias around the required common-mode voltage.

    If using a DC coupled approach, the analog inputs must be centered around VCM. In this case, the VCM output is usually used to provide this level to an amplifier. 

    Regards,

    Jim