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ADS1299: Real time lead off detection

masahiko hayase
Prodigy 40 points
Part Number: ADS1299

Hello,

Our device under development is designed to monitor lead off status while measuring EEG signal by using ADS1299's lead-off excitation signals.
Is there any downside in signal quality by the lead-off excitation signals except for DC input impedance(1G ohm min. to 500Meg ohm typ.), such as input-reffered noise ?
In that case, how much will the signal quality deteriorate?
I recognize offset voltage degradation.

device settings
- 8ch eeg with ADS1299.
- each channel is connected to negative input.
- reference signal is connected to positive input via SRB2.
- Bias signal is used as DRL.
- ILEAD_OFF:00h(6nA), FLEAD_OFF:00h(DC), LOFF_SENSP:80h, LOFF_SENSN:FFh, LOFF_FLIP:AAh.

Best Regards,

  • 0
    TI__Mastermind 19815 points

    Hi,

    For DC resistor, it depends on the Pull-up or down resistor customers select as well as the external impedance.

    For DC current method, it will introduce some offset depending on the current selected and the external impedance.

    For AC current lead off detection, customers will need to do post DSP and/or algorithm to clean up/extract the signals of interests.

    Above exist due to the nature of ohm's law and kirchhoff's law.

    Thanks