Background
At some point I needed an isolated FTDI. Since I could not find one to buy, I designed one. After talking to some people in the hackerspace with different ideas about the project I designed it so that lots of options are possible with the design.
You can choose between the ADuM 1402 and the ADuM 5402. The 1402 will need some power on the isolated side while the 5402 can deliver up to 60mA via an internal isolated DC/DC converter.
I started with the design from sparkfun: FTDI Basic Breakout which I really liked, thanks for making the design open source, it saved me time.
Features
The features of this FTDI are:
- galvanic isolation via ADuM 1402 or ADuM 5402 (that’s what all the fuzz is about :) )
- small (15.1*0.61/38,4*15,5)
- Micro-USB-B connector (these are the cables I carry around anyways)
- 5V,5V switched, GND and FTDI connections in a 0.1 grid, so you can stack it onto a Universal PCB (stack a bigger DC/DC Converter for full 500mA for example)
The optional features of this FTDI are:
- RX/TX LED for serial traffic indication (I always use low current LEDs to save power)
- Shield connection via RC element
- ESD Protection (USB) via SRV05 or Würth 82400102
- PTC-Fuse 500mA (USB)
- Instead of PTC-Fuse: Current Limiting Power Switch 500mA (MIC2005A-1YM5 or similar)
- USB Bus Powered with Power Switching Configuration (see page 25 of the FT232R datasheet)
The optional features of this FTDI with the Adum5402 are:
- Switch for output voltage selection (3.3V / 5V)
- LEDs for voltage selection feedback (same colours as the cables in your ATX power supply ;) )
- Current Limiting Power Switch 50mA to protect the ADuM5402 (MIC2090-1YM5 or similar)
Design Files
Circuit: Datei:Isolated versatile FTDI.pdf
Eagle files: Datei:Isolated versatile FTDI.zip
Finished PCBs
- Soldered PCBs
FTDI adapter in action
Back side FTDI adapter
Front FTDI adapter extended version
Front FTDI adapter simple version
Stacking FTDI adapter with DC/DC converter
Stacking FTDI adapter with DC/DC converter (500mA)
Traco Power:
TMR 3-0511 5V
TMR 3-0510 3V3
PCBs
First PCBs are ordered and we will solder them in a few weeks. Progress:
Bill of Materials / Jumper Configuration
basic
- solder SJ_VE1
| Quantity | Part Name | Value/Part No | Size |
|---|---|---|---|
| 1 | PCB | ||
| 1 | USB Connector MICRO B | ZX62-B-5PA(11) | |
| 1 | .1 inch Header 6P | ||
| 1 | ADuM1402 | ||
| 1 | U1 | FT232RL | |
| 4 | C2, C3, C4, C6 | 100nF | 0402 |
| 1 | C9 | 10µF | 1206 |
RX/TX LED for serial traffic indication
| Quantity | Part Name | Value/Part No | Size |
|---|---|---|---|
| 1 | LED_TX | LED red (2mA) | 0603 |
| 1 | LED_RX | LED green (2mA) | 0603 |
| 2 | R1, R2 | 2K2 | 0603 |
Shield connection via RC element
| Quantity | Part Name | Value/Part No | Size |
|---|---|---|---|
| 1 | R3 | 330R | 0805 |
| 1 | C7 | 220nF X7R | 0805 |
ESD Protection (USB)
| Quantity | Part Name | Value/Part No | Size |
|---|---|---|---|
| 1 | SRV05 |
PTC-Fuse 500mA (USB)
- cut SJ_VBUS
| Quantity | Part Name | Value/Part No | Size |
|---|---|---|---|
| 1 | PTC_FUSE | PTC-Fuse 500mA | 1812 |
Current Limiting Power 500mA (instead of PTC-Fuse)
- cut SJ_VBUS
| Quantity | Part Name | Value/Part No | Size |
|---|---|---|---|
| 1 | MIC2005A-1YM5 | ||
| 1 | C5 | 1µF | 0603 |
| 1 | C9 | 100µF | 1206 |
Power Switching Configuration
- cut SJ_5V_SW
| Quantity | Part Name | Value/Part No | Size |
|---|---|---|---|
| 1 | Q1 | IRLML2244TRPBB | |
| 1 | R6 | 10K | 0603 |
| 1 | R7 | 1K | 0603 |
| 2 | C1, C8 | 100nF | 0402 |
ADuM5402
| Quantity | Part Name | Value/Part No | Size |
|---|---|---|---|
| 1 | ADuM5402 | ||
| 2 | C10, C11 | 10µF | 0603 |
Switch for output voltage selection (3V3/5V)
- cut SJ_V+_5V
| Quantity | Part Name | Value/Part No | Size |
|---|---|---|---|
| 1 | S1 | SSK-1202 |
LEDs for voltage selection feedback
| Quantity | Part Name | Value/Part No | Size |
|---|---|---|---|
| 1 | LED_3V3 | LED orange (2mA) | 0603 |
| 1 | LED_5V | LED red (2mA) | 0603 |
| 1 | R4 | 2K2 | 0603 |
| 1 | R5 | 1K | 0603 |
Current Limiting Power Switch 50mA to protect the ADuM5402
- cut SJ_V+
| Quantity | Part Name | Value/Part No | Size |
|---|---|---|---|
| 1 | MIC2090-1YM5 | ||
| 1 | C12 | 10µF | 0603 |
License
Licensing CC v3.0 Share-Alike (http://creativecommons.org/licenses/by-sa/3.0/)