Isolated versatile FTDI

Isolated versatile FTDI

by: DCEM

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.

PINOUT

+----------------------------+
|  FTDI Board         -> DTR |
|                     <- RX  |
| U                   -> TX  |
| S                      VCC |
| B                   <- CTS |
|                        GND |
+----------------------------+

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/)