USB to 3.3V adaptor for evaluation modules
This work is licensed under a Creative Commons Attribution 3.0 Unported License.
Current Status: Complete
Date: 7th February 2010
License: Creative Commons Attribution 3.0 Unported License
Presented here is a very simple circuit to convert +5V from a USB port to +3.3V, useful for powering lower voltage micro-controllers and other peripheral devices. It was designed to allow development work on a microcontroller board, whilst plugged into the PC, thus saving an extra power adaptor.
The maximum current is around 400mA, taking into account the power dissipation in the linear regulator and keeping within the 500mA current limit of a USB port.
The design uses an LM1117-3.3, which is a low dropout (1.2V @ 500mA) Linear regulator. A small heatsink is used to dissipate excess heat at higher loads.
The power input is a standard USB B plug, output is via 2 x PCB pads with wires to suit the end application.
A single sided PCB layout has been provided.
Click the thumbnail to enlarge
PCB and schematic download
Available here from Github, https://github.com/istedman/USB_3V3_Adaptor
Updated 27 September 2020