EEVblog #244 PSU Power supply part 9/10

[steve632717]

Hello, I am after a bit of help. I am trying to build the Bench power supply unit (Version B) that Dave showed a few years ago. The question that I have is on Version `A` Dave shows that pin 21 labelled AREF on the microcontroller have a 3.3 Volt supply to it, however, when I looked on the plans for version B, the 3.3 v supply has been removed. It still is labelled as AREF and links into C23 but I cannot see where it goes to. I have watched the videos showing Dave placing the traces for Version B, here it stops at C23 and Dave does not have a trace from where C23 and Pin 21 meet.

I have looked through the datasheet for the microcontroller and it says that Pin 21 AREF should go to the DAC.

I have checked the plans for Version C and it shows Pin 21 AREF has been renamed as VREF and is connected to the 2.048 V ref.

My question is should pin 21 (AREF) on the Atmel microcontroller be connected to reference voltage of 2.048v.

Thanks for any help.

Steve

[KC0PPH]

Im not an Atmel guy (i do PIC's) but I always connect VRef+ of my PIC to a buffered output of my reference. I have never used a DAC to generate this reference voltage but dont see an issue with it. IMO connect it to your reference and call it a day. Just make sure the reference voltage is in the correct range... (Tried using 1.023mV on a PIC once and did not work as it needed 2.0v min)...

Hope that helps m8.