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How do I calculate the ADC sample rate for C2000 Type 3 (e.g. F28069) and Type 4 (e.g. F280049) ADCs?

YAMAZAKY
Prodigy 160 points
Part Number: TMS320F28069

dear expert,

there is a question about ADC sample rate of 28069 and 280049. As show in datasheet, sample rate of 28069 is 3.46M, and 280049 is 3.45M.

For 28069, ADC converion time is 13 ADCCLKs(45MHz), then sample rate = 1/(13/45M)=3.46M.

For 280049, ADC conversion time is 21 SYSCLKs (100MHz), and S/H time is 8 SYSCLKs, then the sample rate = 1/[(21+8)/100M]=3.45M.

So which one is correct, if 280049 is correct, then the sample rate of 28069 is below 3.46M, because the ADC sample time is 7 ADCCLKs at least.

  • 0
    TI__Guru 62975 points

    YAMAZAKY,

    Both calculations are correct. The two devices use different ADC architectures with different conversion state machines.

    The F2806x ADC allows for pipelining of conversions such that the sampling phase of Conversion N can overlap with the converting phase of Conversion N+1. Therefore, the effective sampling rate for pipelined conversions on F2806x is 13 cycles (converting phase).

    The F28004x ADC does not allow for overlapping phases between conversions so its sampling rate is the sum of the sampling phase + converting phase.

    -Tommy

  • 0 in reply to tlee
    Prodigy 160 points

    Tommy,

    thanks for your answer. 28004x is the latest device, so does it mean overlapping is not good?  Could you expalin why 28004x make this change?

    YAMAZAKY

  • 0 in reply to YAMAZAKY
    TI__Guru 62975 points

    YAMAZAKY,

    There are multiple factors that contributed to the decision to change the ADC architecture on newer devices. The short answer is that it was the optimal solution based on the trade-offs for cost vs performance.

    -Tommy