I have a PSoC5 set up with some VDDIOx at 3.3V and some at 5V. My VDDA is also 5V. Let's say I connect an internal analog device, e.g. an OpAmp input or output to one GPIO in the 3.3V VDDIOx group. The question is: Is my voltage range on that pin 3.3V or 5V?
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Sounds reasonable, but consider an OpAmp output that is routed to two pins on different VDDIO groups. Since the OpAmp has the output stage and the GPIO pin doesn't, it seems logical to me that both pins output the same voltage. Am I wrong? Why?
If I am reading the I/O system block diagram correctly then the routing doesn't work that way. Rather the digital output path still has clamping diodes connected for the VDDIO group, just with push/pull inactive.
You are probably mixing analog and digital realms. The VDDA is common to the analog world which is separate from VDDD which is for the digital signals. VDDA must be the highest of all VDDs.
Thanks for clarifying, Bob. I thought it was like that. I was just a little afraid that the pins had built in protection diodes to VDDIO also when used as an analog i/o which would limit the analog range to VDDIO. Obviously they haven't.