I'm using a AD5620 nana-DAC part. I have an intermittent failure. Sometimes the part does not respond to serial interface commands. The voltages remains at 0V even though I'm sending serial commands to it. If I cycle the power to the device, the problem will go away. However the problem will often reoccur after another power cycle. I've probed all 3 serial interface signals and the signal timing appears to be correct. Any suggestions? I'm attaching a snippet of the circuit that I'm using.