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negtive input of channels in ADS1299.

Qingxue Zhang69
Prodigy 90 points
Other Parts Discussed in Thread: ADS1299

Hi ,

I am using ADS1299 to collect ecg data. I know the recommended method is to use one channel to acquire the signal: the positive and negative inputs are connected to the left and right arms separately.

But I am trying to use two channels, connecting the positive input of one channel to collect signal from left arm, and the positive input of another channel to the right arm. Then I can try to get the ecg signal in digital domain (channel 1 - channel 2 in digital domain)

So I need to deal with the negative inputs of these two channels. Can anybody tell me how to connect these negative inputs?

As my understanding, the 2.5V input maybe necessary for the negative inputs to meet the input requirements of the amplifier in the channels. Is there a way to provide internal 2.5V voltage to the negative inputs?

Thank you!

Best Regards,

Qingxue

Is it possible to use two channels to collect ecg signal from left and right arms?

  • 0
    TI__Mastermind 38745 points
    Hey Qingxue,

    The on-chip bias amplifier may be configured as a unity-gain buffer for an internally generated analog mid-supply voltage. Refer to the diagram on page 54 of the datasheet for a great illustration of the functionality and control of the bias amplifier. When configured as a unity gain buffer, the BIASOUT can be connected to the negative input of your channels to allow single ended measurement. Alternatively, you could simply bias the negative inputs to mid-supply passively using a voltage divider.

    However, I'm not quite sure I see the benefit to using two single-ended measurements and subtracting them in the digital domain. The noise of both channels will be present with the final measurement. I believe that converting the signal differentially will achieve the better results from a performance perspective and will provide some savings in terms of number of channels used and processing steps. Can you guide me as to your rationale?

    Regards,
    Brian Pisani