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ADS-1299 Reference electrode connection in single ended inputs

deva kumar
Prodigy 10 points
Other Parts Discussed in Thread: ADS1299

Hello,

We're having a hard time comprehending the instructions from pg17 on how to set up the single ended inputs in the ADS1299PDK. We like to start off by using 3 electrodes with one of them being an reference electrodes. Could someone post the configurations of JP6,7,8  and 25 for this setup? Where do we connect the reference electrode(which pin on the board) if we connect the 2 electrodes to pins 36 and 34 of J6?

Thank you

  • 0
    TI__Mastermind 38745 points
    Hello deva,

    The instructions on page 17 of the user's guide assume that the Bias Drive circuit will be used to provide the reference voltage for the electrodes. Your case is different since you have a dedicated reference electrode. There are a few ways to do this. One way would be not to short pins 5 and 6 of JP25, feed your reference electrode voltage directly to pin 6 and internally mux the SRB1 pin to the negative input terminals of the channels in the MISC1 register.

    Another, perhaps simpler, way to accomplish this would be to connect the reference electrode to pin 1 of J25 which will route your signal to the odd numbered pins on J6. You can see then by shorting those pins to the device-side pins that your reference voltage will be routed to pins "AINxN" of the ADS1299 which are just the negative channel inputs. In that case, there is no need to make internal mux changes to the inputs. Just apply your signal to the positive analog inputs and you should be able to measure them with respect to your reference voltage.

    Regards,
    Brian Pisani