DIY 3.3V USB breakout board, LVTTL and LVCMOS compatible

Nowdays 3.3V logic level is gaining popularity, almost every every new microcontrollers are working on 3.3 volt. The worst part is some of them are not tolerant to input voltage above 3.6 volt, while USB is 5 volt.

So if you connect a such microcontrollers to USB directly, probabbly it’s gone !

Here how you can make a simple 3.3V USB breakout board for your microcontroller based projects. It’s a really simple projects, but requires a little patience.

 

Part list

This project requires just few parts,

  1. A USB male connector
  2. A little piece of strip board
  3. One AMS1117 3.3 LDO voltage regulator
  4. Two 3.3V Zener diode
  5. Optional, one 100-220uF tantalum SMD capacitor

You can replace the AMS1117 3.3 regulator with any compatible LDO regulator.

 

Circuit diagram and construction details

Lets have a look at the schematic,

 

The best way to construct this USB breakout by etching a small double sided PCB, unfortunately I didn’t have a copper clad board now, so decided to make it on a strip board.

It took about one hour to build one of them from scratch, below the final result.

3.3 volt USB breakout board

Well, the male USB A connector is a bit rusty !

 

Notes:

While this USB breakout works perfectly with full speed USB devices[ USB 1.1, 12Mbit/s] like a USB AVR programmer or crappy USB hubs, USB optical mouses, but it may not work with USB high speed [ USB 2.0, 480Mbit/s ] devices.

I’ve tested the breakout with a tiny RTL8188CUS based USB WiFi module, which is a USB 2.0 device, just failed to work.

Also tested some USB 2.0 card readers, few of them worked, few of them denied.

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