ADS1261: Fclk frequency

Hi Dennis,

The ADS1261's internal oscillator has the ability to switch between a 7.3728 MHz output frequency and a 10.24 MHz output frequency. This occurs when setting the data rate in the MODE0 register, assuming the internal oscillator is selected, and happens automatically. That is why two different frequencies are shown in the datasheet in Table 7.3.

This means that if you instead choose an external oscillator, you would need to be able to offer both frequencies in order to use the full set of output data rate options offered by the ADS1261. Unfortunately the data rate options <40 kSPS are not specified with a 10 MHz clock, so I would caution against doing this. This is not guaranteed by the datasheet since this configuration has not been tested, and can lead to undefined outcomes. For data rates <40 kSPS, I would recommend limiting the external oscillator frequency to 8 MHz, per the datasheet

-Bryan

Bryan

Thank you for the timely response.  This is unfortunate.  I'm wondering why the external clock option is offered.  I think it would be of great benefit to have the lower sampling frequencies able to use the higher Fmod frequency.  Again thank you.