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Ads1298R Shielding

Evert Dekker
Prodigy 140 points

Hi Folks,

We have reworked the ADS1298R-EVM to measure the respiration with the 4 terminal mode, as shown in sbaa181.pdf.

Also we disconnected the ECG_RA/LA from IN1.

So with this setup we have 7 wires that are going to the patience simulator;
2 wires for the current source, connected to RESP_MOD_N/P
2 wires for the receiver electrodes going to IN1N/P
2 wires for ECG RA,LA connected to IN2N/P
1 wire ECG RLD connected to RLDOUT.

All 7 wires are shielded and the shield is connected to AGND.

This works reasonable, but with still have some noise on the respiration signal on IN1, ECG looks prefect.
To get rid of this noise I was thinking about driving the shielding with the ECG_SHD_DRV , but what to do with the current source wire shielding and current sense shielding? Does it make sense to drive this or will make that the problem worse.

The easiest way would be trying it, but all 7 wires are molded in 1 connector with all shields attached to 1 pin so I have to "operate" the plug to get access to the individual shielding.

  • 0
    TI__Mastermind 38745 points

    Hey Evert,

    On the PCB for that EVM, the shield drive path does not come populated. If you look at the schematic, however, you'll notice that the shield drive is simply the buffered output of the right leg drive. If you were going to use the shield drive, it will be necessary to populate that path. We do not specify an op-amp to use as the buffer. As for the improvement to the noise performance if it were connected to the respiration circuitry shield, I doubt that it would hurt, but I have no reason to believe it would help. If you don't want to make a major change to the connector then perhaps try connecting the shield drive output to the connection for all the shields. I'm sorry I couldn't be of more assistance. Let us know if you try it and get a noticeable increase in performance.

    Regards,

    Brian