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ADS1299: Confused in ADS1299 datasheet

Sara Jia
Expert 2975 points
Part Number: ADS1299

Dear TIs,

     I have one question in ADS1299, as show in the follow Schematic, the input voltage  for ads1299  is reduce to 1/10 of the source, but I calculate the result  by the param.  I can't agree with the datasheet.

if there is some mistake, pls tell me. Thanks a lot.

  • 0
    TI__Guru 66206 points
    Hi Sara,

    Thanks for your post!

    Can you describe your problem in more detail? What is the input signal you are applying and what do the output results look like?


    Regards,
  • 0 in reply to Ryan Andrews
    Expert 2975 points
    Dear Ryan,
    Thanks for your reply.
    Sorry for describing the problem no clearly. I didn't test the circuit. Only refer to the sch in the datasheet as show in the post, for the circuit param, I calculate the result which is not same as the datasheet's result(output is 1/10 of input). I am not sure which is correct.
    Would you give an explanation for the sch and rectify my error?
  • 0 in reply to Sara Jia
    TI__Guru 66206 points

    Hi Sara,

    I think I understand what you mean now, and it looks like you have found a mistake in the datasheet. :)

    The schematic shows a resistor divider circuit of 10.3k and 952k. This ratio will attenuate the input by a factor of 1 / 100, not 1 / 10:

    10.3 / (10.3 + 952) = 0.0107.

    I believe the schematic was drawn incorrectly, but the text description and Figure 75 are correct. Let me double-check with the engineer who wrote this section and get back to you.

    Best Regards,

  • 0 in reply to Ryan Andrews
    Expert 2975 points
    Dear Ryan,
    Thanks a lot.
    Waiting for your reply.
  • 0 in reply to Sara Jia
    TI__Guru 66206 points
    Hi Sara,

    The signal source in the schematic shown in Figure 74 should have an amplitude of 330 uVrms. This is divided down by the resistor divider to provide 3.53 uVrms at the ADS1299 inputs.

    Figure 75 shows the resulting sine wave (referred to the input) after additional low-pass filtering and DC removal of the ADS1299 output.

    Best Regards,