ADS1292: CMRR test issue

Hello,I have tested my system's CMRR,but not quite good,here is my test result:

The test was conducted according to <YY1079-2008>,here post the test circuit;

Then i tested ADS1292FE demo board the same way,here is the result:

;

I,think i should use 4.2V as the Vcm input,because it's the real input;

Here comes my first question:

The ADS1292 FE demo board CMRR test result seems like don't meet the descrition by the white paper <Improving Common-Mode Rejection Using the Right-Leg Drive Amplifier>

Please help me analyze the situation;

My second question is that why in my system after connected the RLD, i have only about 3dB CMRR increase ,but in the demo board it has about 13dB increase which had meet the white paper? and what should i do to increase CMRR about 13 dB when i connect the RLD?

Here post my circuit diagram&my reg value:

After tested the demo board,I did the following test ,i had changed the RLD feed back res(R12) from 110K to 4.7M( C8 was DNP when testing)，but it seems that just have a little influence (about 1 dB) on the CMRR，

that's different from the way I thought it would be; What could be the cause?

Please help to analyze the above reasons,thanks!

Katherine Wang：

已为您联系TI资深工程师，一旦得到回复会立刻回复给您

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Katherine Wang：

请问您的目的和目标是什么呢？此外，我给您的邮件发了一封邮件，以询问一些必要的信息。

通常，对于数据表的 CMRR 验证和验证，我们支持得没有这样深入，因为有太多不同的因素、变化、组件、方程式和程序等可能影响 CMRR 测试和测量的差异。

而且，您几乎无法 100% 完全复制/再现最初在 TI 实验室和测试环境中完成的 CMRR 测试设置。

通常，对于 ADS1292，我们只能提供和披露以下声明 –

参考数据表注 (4)： CMRR 是使用 AVSS + 0.3 V 至 AVDD – 0.3 V 的共模信号测量的。所示值为两个通道的最小值，请参阅第 24 页。

这是我们可以披露的信息，也是TI 允许共享/公开的信息。