Copyright © 2015 Future Technology Devices International Limited

23

FT234XD USB TO BASIC UART IC

Version 1.2

Document No.: FT_000753 Clearance No.: FTDI#324

7 Application Examples

The following sections illustrate possible applications of the FT234XD.

7.1 USB to RS232 Converter

GND

R5

10k

GND

VBUS

C4

10nF

C3

0.1uF

C1

4.7uF

GND

GND

FB1

600R/0.5A

VBUS

1

D-

2

D+

3

GND

4

CN1

USB

C5

47pF

C6

47pF

GND

GND

C2

0.1uF

RXD

10

USBDP

12

USBDM

1

3V3OUT

3

RESET#

2

CBUS0

6

TXD

7

CTS#

11

RTS#

8

U1

FT234XD

R1

10k

C7

10nF

GND

GND

TXD

RXD

RTS#

CTS#

SLEEP#

R3

27R

R2

27R

16

12

13

9

15

10

17

8

C1+

2

C2+

5

GND

18

C1-

4

VCC

19

C2-

6

V-

7

V+

3

EN

1

SHDN

20

NC

11

NC

14

U2

ZT3222F

C10

0.1uF

C9

0.1uF

C11 0.1uF

C12 0.1uF

C8

0.1uF

GND

TXD_RS232

RXD_RS232

RTS_RS232

CTS_RS232

Figure 7.1 Application Example showing USB to RS232 Converter

An example of using the FT234XD as a USB to RS232 converter is illustrated in Figure 7.1. In this

application, a 3V3 TTL to RS232 Level Converter IC is used on the serial UART interface of the FT234XD

to convert the 3V3 levels of the FT234XD to RS232 levels. This level shift can be done using line drivers

from a variety of vendors e.g. Zywyn. A useful feature on some of these devices is the SHDN# pin which

can be used to power down the device to a low quiescent current during USB suspend mode.

A suitable level shifting device is the Zywyn ZT3222F which is capable of RS232 communication at up to

1000k baud.