On one of our boards we need many pins with VDDIO = 1.8V.
We have a 1.8V converter on board, but it should be equipped with an enable input, as
it powers many other components.
The PSoC is powered from and external 3.3V source.
In order to avoid the dependence on an external 1.8V source I wonder whether we
could power one VDDIO-bank from the internal regulator for digital logic, VCCD.
The data sheet says: "The regulator output is not designed to drive external
circuits.", but would VDDIO qualify as "external circuit"?
I could think of using two Shottky diodes and supplying VDDIO from the onboard regulator when it is up,
and use VCCD only to get enough supply to activate the enable output.
I think the IO bank itself doesn't count es external circuitry. But the GPIOs need to supply current to whatever they are connected to, and these currents might be substantial (several milli-amps, depending on switching frequency and fan-out). So you should not use the internal regulator.