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ADS7883EVM: About the analog input type.

ChangHoon Park
Prodigy 200 points
Part Number: ADS7883EVM
Other Parts Discussed in Thread: THS4031, ADS7883

I want use this board for DC analog input.

However, when I powered up the board with below conditions

+VA: +6V

-VA: -6V

VDD: 5V

VCC: 5V,

I had a problem that the analog input had about 1.1V offset voltage.

Is this correct?

I guess that problem is caused by the input buffer stage using THS4031.

please let me know how to use for the DC Vin.

Thanks.

  • 0
    TI__Expert 4405 points
    ChanHoon,

    The ADS7883 can accept a unipolar input from 0V to VDD, which in your case is at 5V.

    The voltage at the non-inverting terminal of the THS4031 is set by the R13 trimpot. If you adjust this trimpot to get an offset of 2.5V when the +IN input is at 0V, this will enable you to feed an input of -2.5V to 2.5V at +IN. As this is connected to the inverting terminal of the Op-Amp, this in turn translates to a signal of 0V to 5V at the input of the ADC.

    Regards,
    Sandeep