16lf1503 and FVR used as Vref+ for ADC

[Sam_63]

I've read though many post here and reviewed the data sheet but, it's still not entirely clear if it's possible to route/use a FVR voltage, say the 2.048V for example, as the Vref+ on the ADC.

The block diagram really doesn't indicate much here but obviously, the FVR line goes into the ADC block but, can this FVR voltage somehow be connected to Vref+ line internal to the ADC block?

.....setup_adc_ports(sAN0 | VSS_FVR2.048); //pseudo code

any help would be much appreciated

[Ttelmah]

Not as the Vref.

First part, look at the data sheet. Figure 15-1, shows the FVR arriving at the ADC input multiplexer, as effectively AN31.

Then read the ADC specs, and see that Vref, can come from either Vdd, or the Vref input pin only.

Key point is that with a fixed voltage available to read, you can effectively calibrate whatever other source you use. So you can select the FVR input as an input voltage, use Vdd as your 'Vref' for the ADC, read the input, and you then can calculate the voltage that is actually on the Vdd pin. You then have a calibrated voltage to work from.
So it is available as a 'calibration' source, but not as a 'reference' source.

Best Wishes

[Sam_63]

Got it, thx Ttel!

Guess I was hoping there was a "un-seen" SPDT switch inside the ADC box for this purpose. That would have been just too convenient, bummer