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ADS1198 RLD Configuration Question

Alan Amin
Prodigy 70 points
Other Parts Discussed in Thread: ADS1198

Hello,

Our ECG device is designed based on ADS1198. Single supply operation, +3 V. We’re trying to configure the RLD setup where RLDOUT pin is connected to the RL electrode per datasheet instruction for common-mode noise reduction. However, there are a couple of questions need to be clarified:

1. Can a combination of channels be used both for RLD Sense amplifier and ECG signal converting at the same time? Or the selected channels must be dedicated to RLD Sense amplifiers only?

2. If decided not to use RLD at all, is it required to use any other voltage reference as a substitute for RLD electrode? This ambiguity comes from the single supply operation where INP inputs are connected to the electrodes without any voltage reference being connected to the body. And all INNs are tied to Mid-supply voltage. We just don’t see an ECG signal current return path without an additional reference!


Regards,

Alan A

  • 0
    TI__Guru 57336 points

    Hello Alan,

    I may have just answered part of this question in my last post.  :)

    1. The ECG inputs selected for RLD sense can also be used to measure ECG simultaneously without any problem.
    2. As I mentioned in the other post, you will need to bias the INxP inputs somehow. Otherwise, the difference between the common-mode signal on INxP and INxN will show up as a differential error at the ADC output.

    Best Regards,