DAC8775: Vref variation and gain/offset calibration

Adrian,

The calibration mechanisms are purely implemented in the digital domain, so they are not capable of overcoming issues like output voltage swing to rail at either positive or negative rails or, as you have pointed out, limitations associated with either the internal or external reference. The calibration features are primarily aimed at the linear region of operation as typically calibration is performed here, not at the absolute zero and full scale codes to avoid any non-linearity (although in this case most situations will be linear since the DC/Dc provides headroom and footroom).

I would mention that a "low" reference doesn't always mean that the DAC output will also be low as positive-going gain or offset errors could overcome this effect, though generally reference error is the largest contributor.

I can work on acquiring the reference distribution information, but we will need to share that offline as it is TI confidential information. As such we will also need to ensure there is an NDA in place with your customer.