ADS1298R: ADS1298R

Ravi Chaudhari1

Prodigy 50 points

Part Number: ADS1298R

Hi,

We are facing issue with CMRR. We are not using RLD amplifier.

We have a few question regarding WCT which is mentioned below.

If we use WCT as a lead channel negative input than should route WCT signal as a differential or parallel or use as a reference like GND?
Is there any routing and design specification for WCT?
should we connect WCT capacitor (100pF) to GND instead of AVSS(If AVSS is -2.5V)?

Regards,

Ravi Chaudhari

over 3 years ago

0 TCT over 3 years ago

TI__Genius 11550 points

Hi Ravi,

Thanks for the post. Please see my comment below.

1. You can route the WCT signal as parallel for the chest leads (V1-V6) input channels.

2. There is no specific design or routing requirement for the WCT.

3. The recommendation is to connect the WCT to AVSS

Thanks.

-TC

0 Ravi Chaudhari1 over 3 years ago in reply to TCT

Prodigy 50 points

Thanks for your response.

We have tried out to resolve the CMRR issue in our device but still, we do not resolve it.

Could you please share RLD implementation details like discrete components value, layout notes and if any? We have tried out as per the suggested datasheet and reference design but don't see any change.

If we route WCT signal parrallel for the chest leads than the reference plane should be AVSS or AGND?

Regards,

Ravi Chaudhari

0 TCT over 3 years ago in reply to Ravi Chaudhari1

TI__Genius 11550 points

Hi Ravi,

Please refer to the application note link below for using the RLD drive to improve the common-mode rejection. The application note explains in detail several techniques to improve the common-mode rejection of an ECG system using the RLD amplifier.

Improving Common-Mode Rejection Using the Right-Leg Drive Amplifier

I also include the link for some older discussions on the WCT below for your reference. Our EVM WCT signal routing is with reference to the AGND with a 4-layer PCB design.

https://e2e.ti.com/support/data-converters/f/73/t/496049

Thanks.

-TC

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ADS1298R: ADS1298R