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ADS1220: Multiple devices

Part Number: ADS1220

Hi Experts,

Good day.

Cx is using multiple ADS1220 A/D converters for a design. Was going to share the DRDY pin between all ADS1220s they're using. They'll have isolated CS input lines for each A/D, but was wondering if sharing the DRDY pin could damage the A/Ds that are not active(CS high) during data transmission of one of the A/Ds.

Thank you.

Regards,
Archie A.

e2e.ti.com/.../ads1220-multiple-synchronous-sampling

  • Archie,

    The DOUT/DRDY pin is a push-pull logic type output.  Connecting two push-pull outputs together can create a conflict where one is outputting a logic zero and the other is outputting a logic one.  This is not advisable as the resultant logic state is indeterminant and the device current can be high.  You could use a logic OR-gate (or multiple OR-gates) if you want to OR the DRDY signals.  Let me know if this helps or if you have further questions.

    Art

  • Hi Art,

    Thanks for the feedback.

    Understanding that the outputs are push-pull, we will only be communicating with one device at a time on the SPI bus pulling the CS low for one device at a time. Won't the remaining non-active ADCs on the bus have floating pins for these outputs during this data transmission?

    Regards,
    Archie A.

  • Archie,

    Dout will go high Z when not being used.  If Dout is configured as Dout/DRDY by setting the DRDYM bit high in the configuration register, it will not go in high Z mode.  The stand alone DRDY pin will never be in high Z mode, it will output a low when data is ready and a high otherwise.

    Art