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ADC Sample and Hold Window

SeAn Kinsella
Intellectual 360 points

I am trying to calibrate an ADC at the moment using external references and I am having a bit of problem with reading accurately the lower ADC voltage 0.049V as my ground is quite noisy.

I would like to try and sample this as many times as I can to get an accurate value and was wondering about the sample and hold acquisition time.

From reading documentation, I believe that the acquisition window that is specified is only for the purposes of charging the sample and hold capacitor.

 

i.e. by increasing or decreasing the sample and hold window value in the ACQPS register I will not make my ADC reading more accurate?

Is this the case?

 

 

  • 0
    TI__Expert 8500 points

    SeAn,

    The ADCPS register is used to control the time that the sample switch is closed and the capacitor is charging. It is useful for high impedance circuits that cannot transfer the charge to the internal sample capacitor quickly. If this is your problem it may help. However, from what you are saying it sounds like the problem is the ground noise. I think you are correct that the length of the sampling time will not necessarily help this. If you have not already done so, try dampening the ground bounce by isolating the analog ground plane from the digital ground plane on your circuit board except for a single point connection as far away from the device as possible.

    Regards,
    Dave Foley