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ADS1198: ADS1198

R_K
Intellectual 385 points
Part Number: ADS1198
Other Parts Discussed in Thread: OPA333

Hi,

We need to determine whether to inatall R16 or R20 in our design to connect U20.3 to either RLDINV or RLDOUT. We have followed "ADS1298ECG-FE/ADS1198ECG-FE" users guide.


Thanks in advance

  • 0
    TI__Guru 66466 points

    Hello Rahul,

    Thanks for your question.

    You would want to use RLDOUT. RLDINV is the feedback path for the internal RLD amplifier, which goes to the amplifier's inverting input. RLDOUT is the RLD amplifier's direct output.

    I see that the OPA333 is being used to buffer the RLD output and drive the electrode cable shielding. Remember that the RLD amplifier is outputting an inverted common-mode signal, used for cancellation of common-mode noise on the body. Please correct me if I'm wrong, but I believe you will want to invert the RLD output before driving the cable shielding. This way, the common-mode noise is actually common to both the electrode signal path and the shielding, which reduces the capacitive coupling between them.

    Best Regards,

  • 0 in reply to Ryan Andrews
    Intellectual 385 points
    Thanks for the reply Ryan.

    Since we are following "ADS1298ECG-FE/ADS1198ECG-FE" users guide." We do not know whether to drive the electrode cable shielding with "RLDOUT" or "RLDINV" as both the options are available.

    We will follow your advice and see if driving electrode cable shielding with "RLDINV" works.