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ADS7885: Clock frequency vs sampling rate

Jejomar Ildefonso
Expert 8830 points
Part Number: ADS7885

Hi Team,

Need your help on this. We need to more information about the clock frequency and sampling rate response of the ADS7885. Our customer would like to know the sampling rate of the ADS7885 when operated at SCLK=30MHz.

We would like to use Figures 25 and 26 of the datasheet about this relationship. However, the 5V and 3V response on Figure 26 was given at SCLK=48MHz and 40MHz respectively. Is this the case? Or we can still use these tables to find the value of the sampling rate with respect to a defined supply current and frequency?

Thanks in advance.

Regards,

Jejomar

  • 0
    TI__Mastermind 24940 points

    Hello,

    The timing requirements given in the datasheet should be used for this information.

    The device can use a SCLK frequency of up to 48 MHZ, when using VDD = 5V. This is then used to find the time for conversion phase.

    If using  an SCLK at 30 MHZ (33.33ns), then conversion time = 11.5* t_sclk = 11.5 * 33.33ns = 383.33 ns

    With this information, the minimum acquisition time is added to find the fastest sampling rate possible at this given sclk rate

    sampling rate = acquisition time + conversion time = 52 ns + 383.33ns = 435.33 ns

    in frequency = 1/435.33ns = ~2.3 Mhz sampling rate.

    Regards

    Cynthia