A-Star 32U4 Micro power question

The User’s Guide and the schematic make it very clear that it is possible to power the A* from the USB connector (+5V) or from an external VIN. The schematic shows a “power selection circuit” selects which source provides the VCC that then powers the device.

Is it also possible to not attach either the USB or VIN, but instead connect a +5V supply directly to the A* 5V pin to power the device? My plan is to derive the +5V from a power bank, so it should be pretty stable.


You could power the A-Star 32U4 Micro with a 5V power source directly through its 5V pin, but you should never connect USB when it is powered that way, since that would short USB power to your power bank. If you want to be able to connect USB to program the A-Star while it is powered through the power bank you will need to sever the connection between USB power and the 5V rail by cutting a trace or removing a component. There are more details on that in this post.


Thanks. Exactly the information I need! I apologize, however, for not finding the the post you reference; gotta work on my search capability.