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ADS127L11: Can someone please clarify data sheet

steve smith1
Prodigy 220 points
Part Number: ADS127L11

Hi can you please someone please clarify the data sheet. On page 1 it says 1.067MSPS sample rate but on page 7 SNR is specified with an OSR of 64. Does this mean that to get the SNR specified with an OSR the throughput is only 1.067MSPS/64 = 16.66kSPS ? If so what is the SNR and DNL at 1067MSPS/400kSPS ? Just a bit confusing. Thanks.

  • 0
    TI__Mastermind 36130 points

    Hello Steve,

    The OSR and clock frequency determine the overall data rate.  The SNR is a function of several settings including OSR, filter type, and reference voltage.  Tables 7-1 through 7-5 provide the noise levels for all of the filter configurations.  Please refer to Table 7-2 for the detailed noise performance of the SINC4 filter. This table provides the dynamic range, but you can estimate SNR by subtracting 1.5dB from the dynamic range value.

    If you want a data rate of 1067ksps, then the external clock would be set to f-CLK=25.6MHz and the OSR set to 12.  In this case, the Dynamic Range for the SINC4 filter will be 91.6dB.  You can estimate SNR as 90.1dB from this table.  Similar, for 400ksps, the Dynamic Range is 111.2dB, and SNR can be estimated as 109.7dB.  

    We do not specify DNL since it is much lower than the noise level, and is impractical to test due to long test times for 24b ADCs.

    Regards,
    Keith Nicholas
    Precision ADC Applications

  • 0 in reply to Keith Nicholas
    Prodigy 220 points

    Thanks Keith most helpful