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AM2434: How to Set the Acquisition Time

Ken Chung
Prodigy 10 points
Part Number: AM2434

Hello,

I understand that the purpose of Acquisition Time is to allow the S+H (Sample and Hold) capacitor to reach the voltage level of the external circuit.

The AM2434 DataSheet and Technical Reference Manual (TRM) both explain how to set this (through SampleDelay), with the maximum setting being 257 SMPL_CLK and the minimum as 2 SMPL_CLK.

However, I can't find any explanations or formulas to calculate the appropriate Acquisition Time.

Should I base everything on experimentation?

  • 0
    TI__Intellectual 2076 points

    Hi Ken,

    Apologies for the delayed response. The Aquisition window is usually based on the sampling rate requirement for the given input signal, and hence can be made so that the Sample and hold circuit charges enough, while the signal itself doesn't change while sampling. We have requested a HW expert to return for better response.

    thanks

    Madhava

  • 0
    TI__Prodigy 10 points

    Hi Ken,

    You can referrer to this application note for C2000 ADCs to better understand how to select the acquisition window based on the characteristics of the signal you are trying to observe. https://www.ti.com/lit/SPRACT6

    Here are the parameters for the AM2434 ADC:

    Parameter Value Notes
    vfs 1.8 ADC reference voltage
    Vermax (uV) 219.7266 Max sampling error
    Tsh User selected based on application sample rate reqs
    Ron 200 Sampling switch on resistance
    Ch 5.5pF Sample and hold capacitor
    Cp 5.5pF on die parasitic capacitance

    Best Regards,

    Brian