Of the following pins, which ones are "latched" in at time of power-on reset of AD5421?
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.
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.
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.
Considering the maximum supply current drawn from the DVDD of AD5421.
These would already be equal to 5.15mA. We haven't even added the current drawn from the pull-up resistors, LEDs etc.
I have one more doubt on AD5420. If I don't provide AVDD and if DVCC select is not connected and if I connect 3.3V to DVCC externally whether AD5420 consumes 1mA from external voltage that I have connected?
Nidhi P Shetty