Using external clock for ADS1292R EVM does not work.

Hi Peter,

Correct me if I’ve missed something, but from reviewing the datasheet for the ADS1292R, the only two external clocking options are 512 kHz and 2.048 MHz. To confirm that we’re looking at the same thing, I’ve attached a screenshot of page 40 of the ADS1292R datasheet. Changing the System Frequency Selection is important such that the internal clock divider is always feeding the modulator a 128 kHz clock signal. If a 512 kHz external clock is used, that frequency will be divided by 4. If the 2.048 MHz clock is being used, the external clock gets divided by 16.

As for your question about the device’s sensitivity to smaller changes in the clock frequency, you can also see from the datasheet that it is possible to clock the device at other frequencies that are relatively close to the "ideal" ones. For example, the datasheet specifies a valid range of 485 kHz to 562.5 kHz for the “512 kHz” clocking option and 1.94 MHz to 2.25 MHz for the “2.048 MHz” clocking option. What you will have to remember, though, is that the data rates specified in the datasheet will scale by the same factor as the master clock frequency. So if instead of 2.048 MHz you fed the device a 2 MHz clock, and you had configured the device in the 500 SPS data rate mode (bits 2-0 of the CONFIG1 register set to 010), the data rate that you would measure would be ≈488.3 SPS.

Let me know if this helps,

Brian