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ADS1261: Synchronizing multiple ADC

Dan Brouillette
Prodigy 135 points

Part Number: ADS1261

Do you have any recommendations for synchronizing these chip, we have multiple in our design and would like to be able to synchronizing them as close as possible

  • 0
    TI__Guru 58701 points

    Hi Dan,

    The ADS1261 has a START pin that can be toggled to get all devices to start simultaneously (though there might be some very minor delay if the trace lengths between the host and the ADCs are different). Therefore, every time you wanted to start a new conversion, you would just toggle the START pin.

    -Bryan

  • 0 in reply to Bryan Lizon86
    Prodigy 135 points

    Do all the ADCs need to be using the same clock source as well, or can they use their internal clocks? and does this need to be done after each read to maintain synchronization or can it just be done once? 

  • +1 in reply to Dan Brouillette
    TI__Guru 58701 points

    Hi Dan,

    The oscillator, whether internal or external, will have a tolerance that directly impacts the ADC conversion latency (the time it takes from the start of conversion to the time that new data is available). For example, the ADS1261 internal oscillator tolerance is 0.5% typical, 2% maximum.

    The conversion latency values given in Table 8 in the ADS1261 datasheet directly correlate to the clock frequency, so if the oscillator shifts by 2%, so do these values. This can increase or decrease the values shown in Table 8 depending on if the tolerance is positive or negative.

    This likely doesn't matter too much for a single conversion, but many conversion over a long period of time might start to get out of sync in terms of when the ADC actually starts converting.

    Therefore, in your situation, it is likely best to toggle START after each read.

    -Bryan