# ADuC702x MCU bandgap voltage reference question

I have recently started using the ADuC702x MCU family. I plan on using the analog to digital converter that comes with the MCU. The datasheet states that there is an internal 2.5V that it uses for its bandgap voltage reference for its ADC. I would like to use 0V to 3.3V for my ADC application.

On the datasheet, page 50 in the Band Gap Reference section, it states that an external reference input on the Vref pin can be used but must be able to overdrive the internal 2.5V.

At first glance, I figured I could simply connect to my 3.3V rail to Vref to "overdrive" it and program REFCON = 0x00. However, the term "overdrive" has bugged me. Furthermore, I have done some research on this and all online schematics show using the internal 2.5V reference. If it was easy to change Vref, I figured I'd see something other than 2.5V being used.

Has anyone ever used the ADuC702x family? Any help and guidance would be appreciated. Thanks!

I see nothing in the datasheet that indicates what "low drive capability" means, but it's probably pretty low, hundreds of uA or a mA or so. The source impedance is given as 70$\Omega$ but that does not reflect drive capability.