Get Variation in signal

Hi Surender ,

Could you let us know which product this concerns to better assist you?

Thanks,
Francis

A variation of 3–5 mV on a signal that is only 1–80 mV is quite significant. Since you've already removed the MCU and the fluctuation remains, the MCU input is unlikely to be the cause. I would focus on the network around R341, R342, R326, and the REF_CT node. Check whether REF_CT is stable and free of noise, as any disturbance on the 0.632 V reference can couple into the differential signal path. Also verify resistor values, solder joints, leakage paths, and nearby switching or high-current circuits that could be introducing noise. An oscilloscope measurement on both sides of R341/R342 relative to REF_CT may help identify where the variation is being injected.