im planing to make my very own arduino design based on the Arduino PRO mini. I picked this board instead of the UNO mostly because it's way more simpler compared with the UNO since the USB-to-Serial part is missing. As many of you know the MINI uses the 328P-AU which is the SMD version of the 328P however since the AU version is too small for me i would like to use the PU (UNO's chip) instead. From the datasheets the only difference is a small change in the pins position. And the one million dollar question is: Is there any difference on those 2 chips? If i try to use the same design just with the PU model is it gonna work?

3 Answers 3


The -AU and -PU suffixes on the part name indicate different packages. The former is used for the "32A" package (32-lead TQFP), and the latter is used for the "28P3" package (28-lead DIP). In plain English, the -AU is a surface-mount part, and the -PU is a breadboard-friendly chip.

As far as functionality, there is virtually no difference. The 32A package exposes pins for ADC6 and ADC7, which are not available on the 28P3 package, but they are otherwise identical. (Note that these pins are only used for the ADCs; they are not a member of any port, and thus cannot be used for digital I/O.)

  • There's also an -MU which is QFN surface mount.
    – kelin
    Sep 7, 2019 at 21:15

There is no difference as far as Arduino is concerned. I think the AU has a couple extra pins (analog ins), that you might want to route to header locations in a surface mount design, but if your design is based on an Uno, them you can also just leave those pins disconnected with no impact.


I would go with the PU version because you can work on a breadboard with it for testing. If you are going to make a surface mount this to a PCB then use the AU. Regarding the actual difference forgetting about form factor, there is none.

  • 1
    You are wrong, the SMD version has two additional ADC inputs (ADC6 and ADC7).
    – alexan_e
    Mar 9, 2015 at 19:12

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