DAC7563: output status when enable internal ref after POR

Hollis, 

I apologize for the delays. Uttam had some conflicts as of late and it looks like this thread slipped from our attention during that time.

Hollis Liu said:

When without external REF, after POR, no SPI config, what's the status of DAC output, 0 or mid-scale or other status?

In this case the output would depend on what voltage is present at the VREFIN pin. If it's floating then the output potential is this voltage / 2 by default.

Hollis Liu said:

When without external REF, after POR, enable internal REF, what's the status of DAC output, 0 or mid-scale or full-scale? 

The DAC7563 is the power-on reset to mid-scale orderable, therefore the output voltage would be set to midscale for the internal 2.5V reference which is set to a gain of 2 by default for the internal reference, so the output should be 2.5V.

Hollis Liu said:

After POR, If we config the gain=1 firstly, then enable internal REF, will it reset the gain to be 2?

The action of enabling the internal reference sets the gain to 2. So immediately after enabling the internal reference the gain is set to 2.

Hollis Liu said:

After POR, If we config the dac code to be quarter-scale firstly, then enable internal REF, will the output to be 2.5V?

The DAC code is set to mid-scale from the POR circuit. If after the POR the DAC code is set to any value the DAC data register will maintain that value. When the internal reference is enabled the gain is set to 2 for an internal reference of 2.5V for a full-scale range of 5V. At quarter scale the output voltage should be 1.25V.

Hollis Liu said:

When without external REF, after POR, enable internal REF, what's the status of DAC output, 0 or 2.5V?

2.5V.