How do I disable analog input on SPC5674

[tommyhollingswo]

I am using the SPC5674FF3MVV3.   I do not want to use any external analog inputs, and I do not have 5 volts available.   What all is needed to disable the analog in and what do I do with the analog power supplies?

[davidtosenovjan · Accepted solution]

VDDA is needed to connect to 5V even if eQADC is unused. Unused Analog inputs should be pulled to ground.

[tommyhollingswo]

Thank you for the quick response.  Since VDDA is required to be 5 volts, what does paragraph 4.6.3 in the datasheet mean to VDDEH?  Is VDDEH required to be within 1V of VDDA or is that only during reset?  The spec allows VDDEH to be from 3.0 to 5.5 volts, so I assumed 3.3V would be acceptable. Was I wrong?  I also find the following a bit confusing when using the voltages I have:

Each VDDEH will have a leakage current to VDDA of a magnitude of ((VDDEH–VDDA– 1 V(diode drop)/200 KOhms) up to (VDDEH/2 = VDDA+1V)

3.3-5-1/200K

Cheers.

Tommy

[davidtosenovjan]

Mentioned paragraph says “VDDA can lag other supplies” what means it describes situation VDDA is lower than VDDA. It does not happen when VDDEH=3V and VDDA=5V. Basically VDDA should be always higher than rest of sources (or not to be lower by more than 1V).