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AD5421 Power On Reset

Of the following pins, which ones are "latched" in at time of power-on reset of AD5421?








  • Hi,

    The AD5421 powers on with all registers loaded with their default values and with the loop current in the alarm state set to 3.2 mA or 22.8 mA/24 mA (depending on the state of the ALARM_CURRENT_DIRECTION pin and the selected range).

    The most pins that you mentioned are input pins in a sense that the part will power up and will set settings of the part depending on the values of these pins.



  • Hi,

     I am Using this AD5421 in 4-20 mA mode.

    Ans I am not able to set current less than 6.5 mA but above 6.5mA i am getting all the values.

    Please let me know what is the issue.



  • Hi Anush,

    Are you using the internal voltage regulator to supply other components? The maximum current that can be drawn from the REGOUT pin should only be 3.15 for you to be able to set the loop current to 4mA. I'm thinking that in your circuit you are drawing 6.5mA from the regulator so you can only set loop currents greater than this value.

    Best regards,


  • Hi,

    Thanks for your reply.

    Yes, Iam using the power from DVCC pin to power up the isolators and the HART modem AD5700.

    As per Current  calculation the total current taken by the isolators ADuM1441 will not exceed 3.15mA.

    I have attached the schematics for you reference.

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