Question with ADS1222

Yoyo,

I'm not sure what you are asking, but I'll try to explain some of the details of the ADS1222. Hopefully that will answer some of your questions.

From the datasheet, the modulator clock runs at fclk/32. With a 2MHz clock this means the modulator runs at 62.5kHz. Now since the data rate is roughly 120SPS, there are 520 modulator clocks for each data. This gives 62.5k/520 = 120SPS. So the oversampling ratio is 520.

In the ADS1222 this is fixed in the digital section. It cannot be externally changed. The only thing that will change the 120SPS data rate is changing the master clock. For example, a 4MHz clock will give you a data rate of about 240SPS.

If you want to get a better noise performance and are willing to live with a lower data rate, you should be able to average several readings. Generally, the noise will drop with the root of the number of samples. For example, if you average 4 data, you will reduce the noise by two, but only get 30SPS for a data rate.

If you have more questions, please post again.

Joseph Wu