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ADS1292R: how ADS1292R do RLD lead-off detection during normal operation

Bill Xu
Intellectual 1040 points
Part Number: ADS1292R

Dear product line engineer,

     my customer have one issue with ADS1292R: how to do RLD lead off detection during normal operation with ADS1292R?

     I have one question: what is function of R35 in schematic of EVM user guide? please refer below figure from ADS1292R EVM user guide. the R35 connected between non-inverting input and output of internal RLD OPA, seems this is a positive feedback, does this will cause potential risk of oscillating or instable? 

 

thank you very much for supporting. 

regards,

Bill

  • 0
    TI__Mastermind 19815 points

    Hi,

    Which Lead-off detection methods is customer interested in using? Please refer to ADS1292R datasheet page 33~34, there are

    1. DC Pull-Up/Pull-Down resistors methods,

    2. DC current method and

    3. AC lead-off method.

     ADS1292R datasheet page 39 provides a reference register settings for lead-off detection using 2.DC current method.

    The first two methods may not be used simultaneously with ECG sensing using the same channel. But, customer may try to use DC Lead-off detection to make sure there is no lead off before and/or after a ECG sensing session, but not during the ECG sensing session.

    To use lead off detection simultaneously with ECG sensing in the same channel, customer may use method 3. AC lead-off detection.

    If customer is referring to RLD lead-off detection, please refer to  ADS1292R datasheet page 35; however, RLD Lead-off detection cannot be used simultaneously when the RLD amplifier is powered on. "RLD lead-off at power-up function cannot be used because it is necessary to power off the RLD amplifier." and "When the RLD amplifier is powered on, the current source has no function" 

    Regard to R35, Does customer try to do Rerouting the Right Leg Drive Signal or not?

    R35 is optional depending how user want to use the RLDIN/RLDREF pin. Please refer to ADS1292R datasheet page 31 and 32 (Rerouting the Right Leg Drive Signal), 

    If customer is thinking to do route the RLDOUT to input channels, R35 needs to be installed and RLDREF_INT may need to set to 0 to prevent the unstable.

    Thanks.

  • 0 in reply to ChienChun Yang
    TI__Intellectual 1040 points

    Hi, Chienchun

    here is customer schematic and register configure. seems customer use AC lead off method. .

    any other problem, please let me know. thanks

    Bill

  • 0 in reply to Bill Xu
    TI__Mastermind 19815 points

    Schematic Review and reply have been brought to email thread.