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ADS1158: External Clock Source Considerations and Recommendations

Joe Martin
Prodigy 20 points
Part Number: ADS1158


We are moving from using the internal oscillator with external crystal to a clock generator for the ADS1158 ADC. Are there any particular points of interest to pay attention to when selecting a clock source? Does TI recommend a particular part that is known to work optimally? Are there any layout considerations that should be taken into account? 

After a few years of headaches with the 32kHz crystal, we'd like to be absolutely sure we cover all our bases.

  • 0
    TI__Guru 53156 points

    Hi Joe Martin,

    There is a note in the ADS1158 datasheet (page 40) that states "For best performance, the clock of the SPI interface controller and the converter itself should be on the same domain."

    Under certain circumstances (typically at the highest data rates and using Fixed Channel mode) I have seen issues in the output when using asynchronous clocks. I am not sure if you would see these issues with a 16-bit converter, since the spikes I saw were ~50-100uV, but it is possible. Therefore, I would follow the recommendation in the datasheet and use synchronous clocks.

    Following best layout practices should be sufficient e.g. solid ground planes, don't cross analog and digital (especially clocks), etc.

    -Bryan