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ADS1299: ADC

leo chen
Prodigy 235 points
Part Number: ADS1299
It is found that CMRR is about -95, with a slightly worse index, which is far less than the typical value （-120）of ADS1299,What happens if this parameter fails，thx.
  • 0
    Prodigy 235 points
    The most important question is how to improve the problem, thank you
  • 0 in reply to leo chen
    TI__Guru 55062 points
    Hi Leo,

    Thanks for your post and welcome to the forum!

    What are the conditions that the test was performed under?

    Using the highest grade equipment as well as an EMI shield are necessary to improve the CMRR value.
  • 0 in reply to Alexander Smith
    Prodigy 235 points

    hi，alexander

            thx for your reply.The results were obtained by the dedicated common mode rejection ratio test tool, which is a medical device.

            The typical value of -120 provided by TI is tested under the condition of good shielding effectiveness？Can you provide your company's detailed testing methods，thx.

  • 0 in reply to leo chen
    TI__Guru 55062 points
    Hi Leo,

    I am not familiar with the tool that you are referencing. Was the test aligned with IEC60601-2-37? If so that is a different one than what is in the datasheet.

    To the best of my knowledge, the inputs are shorted together and a common-mode sine wave at 50Hz and 60Hz is applied. The peak-to-peak amplitude is equal to AVDD – AVSS – (2 x 300 mV) and DC offset is mid-supply. The device settings are listed at the top of the electrical characteristics table. BIAS is not used in the datasheet test. The test is performed with the device in an insulated shielding box.