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dac7750: DAC7750

John Istad
Prodigy 40 points
Part Number: DAC7750
Other Parts Discussed in Thread: DAC7750

I will be implementing this part in a design without a HART interface.  What do I do with the HART input pin?  Float, connect to GND or 3.3V digital or 12V analog, or connect through a capacitor to GND?  The data sheet SBAS538B of 12/2016 revised 6/2016 does not say, unless I missed it.

  • 0
    TI__Mastermind 46290 points

    Hello John,

    Welcome to the E2E Community and we're glad to hear about your plans to use DAC7750.

    The HART_IN pin directly connects to essentially the same bias point as the 4mA offset for the 4-20mA output span. Of course that means that if the node is connected to any DC potential it will impact the behavior of the current output. Therefore, the only acceptable options are to either float the pin or an AC connection.

    Given the importance of EMC/EMI topics in the applications that DAC7750 is conventionally used in, I would suggest that it is AC coupled to GND so as to ensure that any "rogue" signals that may be in the environment are coupled to GND instead of finding their way into the IOUT signal chain.