My Adafruit 5V Trinket works fine when powered via USB connected to my computer (and the power going in to the Trinket is 5V), but if I use a 9V wall adapter with a microUSB adapter, it just powers on but doesn't seem to actually run the program on the Trinket.

Am I over powering the Trinket and sending too much voltage to everything? If that's the case, is there some way to decrease the voltage?

  • Normally you should never connect more than 5v to a USB connector. This particular board seems to run the USB VBUS through a diode into its regulator, in the same way it routs its VBAT input. So conceivably you would get away with it. But it's still a risky idea to have such non-standard cable assemblies around as they might be accidentally connected to something else that would not tolerate this! A possibility is that your 9v adapter is faulty, or perhaps it outputs AC, or insufficiently filtered DC. Commented May 1, 2016 at 20:21

1 Answer 1


Yes, you are probably over-powering the trinket. The trinket expects 5V on the USB connector. However, it has an voltage regulator on board that can take up to 16V.

The BAT pin is connected to the voltage regulator and can take anywhere from 5.5V to 16V.

  • It's not entirely clear what you are proposing here, but the schematic shows the VBUS and VBAT inputs to be distinct, but have identical circuitry, so an input voltage that is in tolerance for one should be for the other... if only for this particular oddball board. Commented May 1, 2016 at 20:19

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