Other Parts Discussed in Thread: ADS1298
Tool/software:
Hi TI support.
We've built a device using the ADS1298R and have been operating it at 32KSPS without issue on the digital side.
When performing a characterization of gain across frequency we notticed that CH1 has a low-pass cutoff frequency is at 4KHz where as all the other channels are at 8KHz (as expected by the datasheet figures). Please see below for a measured bode plot. - To measure this we swept a sine wave of amplitude within the dynamic range of the system and plotted the output code of the ADS1298R.
On our design we only have external first order passive anti-aliasing RC filters of 10KΩ//470pF before the ADS device. (external RC cutoff is 33-34KHz)
We suspect that this difference is due to the respiration circuitry found only in CH1 as we have used ADS1298 before without observing this issue.
The resp configuration register is at the default value, which we assume to be disabled. Please correct us on this if we have missed something.
Any input from your end that could help us understand the exact cause of this issue would be greatly appreciated.
