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ADS1220: DRDY output. pushpull or open drain

Chuck Jenkins
Prodigy 190 points

Part Number: ADS1220
Other Parts Discussed in Thread: ADS122S14,

Section 8.5.1.3 describes the DRDY dedicated output pin as "The DRDY pin is always actively driven, even when CS is high ". This implies a push pull output yet the DRDY pin description in the pin function table suggests an open pin or use a pull up to VDD if not used.

DRDY 12 14 Digital output Data ready, active low. Leave unconnected or tie to DVDD using a weak pull-up resistor if not used

Figure 72 application suggestion shows no external pull up indicating an open drain but the suggestion of a pull up in the pin description would defeat any low power mode since it is always 'active'. 

Is it push pull or open drain?

  • 0
    TI__Mastermind 25075 points

    Hi Chuck,

    I am sorry that the ADS1220 datasheet descriptions are misleading. In newer datasheets I specifically call out if a pin is open-drain or push-pull in the pin functions table. See our new ADS122S14 as an example.

    The DRDYn pin on ADS1220 is a push-pull output.
    Many customers don't like to leave pins floating when they are unused, which is why I usually also try to provide a guideline for how best to tie off the pin if desired.

    Regards,
    Joachim Wuerker