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ADS1118 Mux switching time

Andrew Chin
Prodigy 220 points
Other Parts Discussed in Thread: ADS1118

What is the mux switching time of the ADS1118? In other words, how long does it take to read input from 1 then move on to input 2? 

  • 0
    TI__Guru* 92655 points
    Andrew,


    The answer is that it varies. If the device is in continuous conversion mode, the change in the mux occurs after the current conversion is completed, and does not change immediately after changing the register.

    If there is a need to ensure the data is correct after a change in the mux settings, it's better to run the device in single-shot mode.

    I would also note that if you do run the device in single-shot mode, there's an extra 20us required for the device to power up and start the conversion.


    Joseph Wu
  • 0 in reply to Joseph Wu
    Prodigy 220 points

    Thanks...

    What we are finding is that we need to send a command just to select the mux, then send a command to read. That is fine. The issue is that it seems to be 16ms worth of delays all together. It seems rather long.  If we make our delays any shorter, we just get the previous read. 

  • 0 in reply to Andrew Chin
    TI__Guru* 92655 points
    Andrew,


    The time in delay is dependent on the data rate. I would think that the max time would be 2*(1/data rate). Imagine that you send the command to set the mux right after the converter started a conversion. It would take all the time to complete the conversion and then set the mux and finally complete the conversion with the new mux setting.

    Again, I think if you need that kind of timing, single-shot mode may be more efficient.


    Joseph Wu