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ADS1120: Enable IDAC after Powerdown without starting a conversion

Andrew Bakin
Expert 1665 points
Part Number: ADS1120

Hi,

I am wondering if it is possible to bring the ADS1120 out of powerdown mode and with IDACs enabled, without it starting a conversion.

My conversion time is 50ms, but my 12*(RC time constant) for the filter is about 8ms. I would rather enable the IDACs for 8ms before starting the conversion. If this is not possible, is the best solution to issue another StartConversion() command after 8ms?

Waiting 50ms for a dummy conversion will waste 42ms of powerup time.

Many thanks,

Andy

  • 0
    TI__Guru** 113765 points
    Hi Andy,

    The ADS1120 does not have a wakeup command, only the START/SYNC command to wake the device which does start a conversion.

    The method you suggest is the easiest to use when needing a delay after the device powers up. Send the START/SYNC command to wake up the ADS1120 and start the conversion and then 8ms later send the START/SYNC command again to restart the conversion from that point.

    Another more complicated method would be to write the configuration register to a higher data rate, send the START/SYNC command to wake the device and wait for the conversion to end. Write the configuration back to the 20sps and send the START/SYNC command again to start conversion at the lower data rate. The advantage of this method is no internal micro delay cycles or timer is required. The disadvantage is there is no data rate that has a period that is precisely 8ms.

    Best regards,
    Bob B
  • 0 in reply to Bob Benjamin
    Expert 1665 points

    Thanks Bob,

    I implemented the second method as this way it would wake my processor in the same way as a normal read without having to use a low-power timer specifically for the job. It works very well and I don't need precisely 8ms, only enough time to lapse to get a 12*timeconstant for the input filters. I ended up with ~17ms which wastes ~9ms but my processor is in very low power mode for this duration with just the ADS1120 running.

    Kind regards,

    Andy