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ADC3643: which schematic is right when use the ADC3643 with diff input

Part Number: ADC3643
Other Parts Discussed in Thread: THS4541,

HI Sir

which one is correct? thanks

  • Hi,

    The image on the left is the most correct since the differential input pins (AINP and AINM) can swing from +1.125V to - 1.125V. The differential signal swing is (+1.125V - (-)1.125V = 2.25V). These voltages must both include the +0.95VDC common mode voltage (VCM) which can be supplied from the ADC pin VCM.

    The THS4541 fully differential amplifier is used on the ADC3643EVM to provide the differential input (with the VCM) to ADC analog inputs. Please see the ADC3643EVM for an example of  how to use the THS4541.

    Best Regards,

    Dan