ADS1261: Data and noise rate

Hi Shotaro Sakai,

Here are the answers to your questions:

1. As long as you choose a low-jitter, high accuracy clock for the system, you should not see any additional noise:
   1. Clock jitter can indirectly add noise to the system creating sampling uncertainty. However, this is usually more relevant for higher-speed ADCs, while the ADS1261 is considered a lower-speed ADC. Oscillators typically have jitter values on the order of picoseconds, which would be good for the ADS1261.
   2. Oscillator accuracy can also indirectly add noise since this directly affects the ADC digital filter response. So if you are trying to reject 50 Hz for example in your system and your external clock oscillator has very bad initial accuracy e.g. 10%, the digital filter frequency null might not fall exactly at 50 Hz. Instead it might be at 45 Hz because the clock frequency is different than the nominal. Therefore, there will be very little 50 Hz rejection, which can look like noise in your system. However, this is really due to the poor accuracy of the clock
2. I would check out the following app note about conversion latency. Section 8 provides many examples of how to calculate conversion latency, including for the ADS1261: https://www.ti.com/lit/sbaa535

-Bryan