TM4C1231D5PZ: VREFA is not 3V3

Ayrton Leyssens

Prodigy 191 points

Part Number: TM4C1231D5PZ

Is the following a problem?
We use 2,5V as VREFA+ while our VDDA is 3,3V.

The datasheet seems to say the minimum for VREFA+ is 2,4 and a typical is VDDA (which is minimum 2,97V).

In the driverlib code (TivaWare_C_Series-2.2.0.295), driverlib/adc.c, ADCReferenceSet has a comment that says

If \b ADC_REF_EXT_3V is chosen, then

//! a 3V reference must be supplied to the AVREF pin.

Please any advice on this.
I added below part of our schematic to make VDDA and VREFA more clear.

over 1 year ago

0 Charles Tsai over 1 year ago

TI__Guru**** 191026 points

Hi,

Your VREF+ is higher than the MIN specified on the datasheet so you are fine.

0 Ayrton Leyssens over 1 year ago in reply to Charles Tsai

Prodigy 191 points

Hi Charles

Thanks for the quick reply.

So we can ignore the documentation for the driverlib (3V reference must be supplied to the AVREF pin)?

Thanks :)

+1 Charles Tsai over 1 year ago in reply to Ayrton Leyssens

TI__Guru**** 191026 points

That is correct. The driverlib document kind of assume an external VERF+ that is NOM 3V. It doesn't delve into the real electrical limits as specified on the datasheet.

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TM4C1231D5PZ: VREFA is not 3V3