I'd like to use an Arduino Uno R3 battery powered a datalogger. I want do supply it directly with a Step-Up *regulated* 5Vv rechargable battery powersource at power `pin 5V`. 

I don't want to suppy it with 5V at the PowerJack or `Vin` because it's not necessary an would result in lower voltage when powered with 5V at `Vin` and unnecessary power dissipation at `U1`.

Let's take a look at the schematic: http://arduino.cc/en/uploads/Main/Arduino_Uno_Rev3-schematic.pdf

I've edited it, take a look at the green areas and blue paths (ignore the yellow area at first):   
![enter image description here][1]


Just supplying it at that `pin 5V` however might destroy the linear regulator `U1` that regulates >5V+ `Vin` down to 5V, I fear. 

# Question #

- Is it acceptable and safe to suppy regulated 5V+ to `pin 5V`?
- Should I additionally short it to `Vin` ()?

Unfortunately there's no internal schematic for `U1` (NCP1117ST50T3G) in the [datasheet][2].
# For interest #

Take a look at the yellow area: am I wrong or is the protection diode reversed? Shouldn't it have the catode at `USBVcc`?


  [1]: https://i.sstatic.net/pkWOu.png
  [2]: http://pdf1.alldatasheet.net/datasheet-pdf/view/174874/ONSEMI/NCP1117ST50T3G.html