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ADS1292 without right leg diver

Vala
Expert 1110 points
Other Parts Discussed in Thread: ADS1292, ADS1292R

Hi,


I didn't fine any specific answer for this question. I need to design a ECG measrement device using ADS1292. But the problem is that I can't use the right leg driving. I know that there would be a lot of noise in the output as the common mode rejection is eliminated, but I don't know what to do the probable floaing baseline or consiquently the saturation of the convertor. Any suggetion would be appriciated.


Regards

  • 0
    TI__Mastermind 38745 points
    Hello V324O,

    One common strategy is to use a DC blocking capacitor combined with a voltage divider resistor DC biasing scheme to AC couple your signal. That way, the floating common mode is rejected by the HPF and the desired common mode is set by the resistors. Take a look at the EVM schematic shown in the users guide here and look at the channel 1 inputs: www.ti.com/.../slau384a.pdf

    The part featured is a ADS1292R and the channel 1 inputs are AC coupled because of the respiration functionality of that device, but the concept is the same. There is a capacitor in the input path that provides an AC short and DC block, and the common mode for the signal is set by the large value resistors on the ADC side of the capacitors. Please note, though, that the capacitor and biasing resistors form an RC HPF for AC signals, so bandwidth considerations must be made when choosing components.

    Regards,
    Brian Pisani
  • 0 in reply to Brian Pisani
    Expert 1110 points
    Hi Brian,

    Thanks for the detailed explanation. Please tell me if you think about any other possible problem without RLD.

    Appreciate your help.