Is it allowed to have battery and USB connected to the Trinket(3.3V) at the same time?

I am using the battery to also power other components, so always disconnecting power, hooking USB to re-program and vice-versa is quite time consuming (and I fear to ruin the connectors).

1 Answer 1


From https://learn.adafruit.com/system/assets/assets/000/010/773/original/adafruit_products_trinket3.png?1378223258 it looks OK -- there are blocking diodes D3 and D2 that prevent backfeeding either the battery or the USB +5.

If you are worried, or want to monitor battery-only performance, you could make a special USB cable with the +5 red wire disconnected, and rely on the in-circuit battery to power the device, while still using the USB data lines. See https://www.pjrc.com/teensy/external_power.html Option 2 for an example of the cable surgery.

  • So that worked. Unfortunately I did not really achieve my goal entirely as the ATTiny on the trinket seems only to enter the bootloader when the controller is powerless and the USB-connection to it is made. Not after a Reset. So back to square 1 :-)
    – Heiko Rupp
    Commented Dec 5, 2015 at 8:39

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