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ADS124S06: device not wake up after powerdown

PLCmatic
Prodigy 90 points
Part Number: ADS124S06

Hi all,

we noticed a strange behaviour from ADS124S06. It seems that after a POWERDOWN command the device could not wake up anymore unless we send this command sequence:

STOP

WAKEUP

START

We want to powerdown the converter because we have two MCU that are reading the converter and the conversion result must be the same for both microcontrollers. So we think that we could obtain this behaviour if we powerdown the converter.

Are we missing something?

The converter is configured in this manner:

- pga bypassed

- continous conversions

- sample rate: 5 sps

- Reading from AIN4-AIN5

- Oscillator: internal

- Voltage reference: external (5Vd.c.)

  • 0
    TI__Guru** 112935 points

    Hi PLCmatic,

    The behavior you are expecting is similar to using START/SYNC pin.  When using the START/STOP commands the control sequence is a little different.  Part of the reason is due to the various potential modes of operation so the state machine for controlling the device becomes a little more complicated.  The easiest way to explain it is by reviewing the Operating Flow Chart in Figure 82 on page 58 of the ADS124S06 datasheet.  The normal flow is the device powers up into Standby Mode.  A START command begins a conversion cycle, and if in Continuous Conversion Mode, the path takes on the right-hand side flow.  If the POWERDOWN command is issued, the device immediately powers down and the conversion doesn't complete.  This places the ADS124S06 in a rather odd state.  When the WAKEUP command is issued, the ADS124S06 enters Standby Mode.

    At this point the START command is blocked as there was not a STOP command issued previously.  The STOP command must be issued before the START command is accepted as the device was previously operating in continuous mode.

    The method I would suggest is to issue the STOP command and wait for the conversion to complete prior to the POWERDOWN command.  Then issue the WAKEUP command when desiring to wake up the ADS124S06 and then issue the START command.  Or you could use the START/SYNC pin to control the conversions.  The POWERDOWN command would still be required to power down the device.

    Best regards,

    Bob B

  • 0 in reply to Bob Benjamin
    Prodigy 90 points

    Thanks for the clear explanation. This solves our issues.

    Best regards