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ADS7953 data acquisition

eltury
Genius 3330 points

I am using this part in a new design and it works well. On page 23 of the data sheet it says "The acquisition phase begins on the fourteenth SCLK rising edge. On the next /CS falling edge the acquisition phase will end...."

I'm just curious as to what is actually occurring during acquisition.

Thanks.

Edd

  • 0
    TI__Expert 4405 points

    Edd,

    As shown in the figure on page 23, SAR ADCs work in two phases.

    During the acquisition phase, the ADC’s internal sampling capacitor is connected to the selected analog input pin. At the end of the acquisition phase the sampling switches are disconnected, storing a charge proportional to the input voltage. The device then enters the conversion phase, where an internal DAC and a comparator is used to determine the digital word corresponding to the input voltage.

    The acquisition phase allows time for transients (due to switching and residual charge from the previous conversion) to settle to the correct input value. This timing parameter therefore is critical in the selection and design of the driving op-amp and flywheel circuit used to drive the SAR-ADC.

    Please see the following links for a more detailed explanation on this topic:

    http://www.ti.com/lit/ml/slyp166/slyp166.pdf

    http://www.ti.com/lit/an/sbaa173a/sbaa173a.pdf

    Regards,

    Sandeep