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ADS1212: Synchronizing Multiple Converters DRDY Timing

Hiroaki Yuyama TED
Expert 1740 points

Part Number: ADS1212

Dear, support team.

Our customers are using Synchronizing Mutliple with Four ADS 1212.
Writing 0xe 3 to command register byte 3
Pull up the DSYNC pin.

Only one DRDY will assert early.
The customer's figure uses DRDY and CLK inverted.

Why is DRDY not at the Synchronous timing?

Best Regards,
Hiroaki Yuyama

  • 0
    TI__Guru** 113765 points
    Hi Yuyama-san,

    The customer should not be using both register write of the DSYNC in the command register 3 and the DSYNC pin in the same synchronization sequence as this will create confusion as to when the DSYNC should actually take place.

    For all converters to be synchronized, the same clock, turbo mode and decimation should be used. It would appear that in most cases the alignment is correct for DRDY and the zoom shot shows device 1 is off in this case. If there is a state error from using 2 methods of synchronization there could be an issue. So again, I suggest using just one method.

    Best regards,
    Bob B
  • 0 in reply to Bob Benjamin
    Expert 1740 points
    Hi,Bob-san,

    Thank you for your Advice.
    The customer fixes the DSYNC pin to HI.
    I think that, The DSYNC bit of the command register is used.

    Is it better to activate the DSYNC pin rather than the DSYNC bit of the command register for synchronization?

    Best Regards,
    Hiroaki Yuyama
  • 0 in reply to Hiroaki Yuyama TED
    TI__Guru** 113765 points

    Hi Yuyama-san,

    In general, the rising edge of a pin signal is easier to decode as opposed to a command register write.  As I do not have a schematic to review the communication signals or how the DSYNC pin might be controlled it would be difficult to say if there is one method better than the other.

    For the command register write function to synchronize properly, all devices must be written at the same time using the same command sequence.  As this process requires communicating to 4 devices with 4 separate CS lines, this would seem more complicated than pulsing the DSYNC pin.

    Best regards,

    Bob B

  • 0 in reply to Bob Benjamin
    Expert 1740 points
    Hi,Bob-san,

    Thank you for your Answer.

    We propose the synchronization of the DSYNC pin by communicating the difficulty of 4 channel simultaneous command sequence and timing to the customer.

    Best Regards,
    Hiroaki Yuyama