The datasheet AD5443 mentioned 'Power-on reset with brownout detection' as a feature but without any further details? Can more details be supplied? I have a design that if I power cycle too quickly (~2 seconds) then the DAC chip ignores the serial data-stream. Does the power rails need to fall to a low voltage to reset the chips logic?
This is not my specific area, but there is general information on brownout detection in this Analog Dialogue article. Also, note the discussion about residual voltage when the supply is disabled. If the supply voltage does not go completely to ground, it may not reset properly. If you wait longer when cycling power, does the problem occur? Can you probe the supply pin and confirm the voltage is not held a diode or more above ground?
I monitored the power rails at power down and they are < 100mV. The misbehavior happens more at low temperature -40C and it difficult for me to probe the IC at low temperature.
I have since tested with the Texas Instruments DAC7811 and it does not suffer from this power up problem. So I am concluding that it is a bug in the AD part. I will be changing to TI on this part.