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AD5421 Loop supply disconnection impact on registers

Hi Team

I'm using AD5421 in my design. In working condition of DAC (When both loop supply and MCU power is available). I'm able to see proper control register value and fault register value is zero.

When Loop supply is disconnected and MCU power is still there for a small interval of time (1 or 2 secs) I was observing fault register as 300.

After that both control and fault registers becomes zero. (Note: IODVDD is not derived from loop supply. It is available always and SPI is referenced to IODVDD as per datasheet).

Why it will not continuously show the fault register value as 300 when 24V is disconnected?

After this I connected 24V back. Now both control and fault register will show it's default state. I hope after this with a initialization of DAC again i should be able to use DAC normally. Please confirm.

Also I need to continuously sense VLOOP using on chip ADC and based on this result I will do further read write operation. Whether this is possible all the time irrespective of 24V condition?

Regards

Nidhi P Shetty