Data Sheet

Copyright © 2013 Future Technology Devices International Limited 25
FT231X USB TO FULL HANDSHAKE UART IC
Datasheet
Version 1.2
Document No.: FT_000565 Clearance No.: FTDI# 261
7 Application Examples
The following sections illustrate possible applications of the FT231X. The illustrations have omitted pin
numbers for ease of understanding since the pins differ between the FT231XS and FT231XQ package
options.
7.1 USB to RS232 Converter
FT231X
1
2
3
4
5
SHIELD
Ferrite
Bead
GND
GND
VCC
GND
VCC
3V3OUT
USBDM
USBDP
VCCIO
VCC
AGND
GND
RESET#
100nF
100nF
10nF
4.7uF+
SLEEP#
CBUS1
CBUS2
TXD
RXD
RTS#
CTS#
DTR#
DSR#
DCD#
RI#
RS232 LEVEL
CONVERTER
TXDATA
RXDATA
RTS
CTS
DTR
DSR
DCD
RI
TXLED
RXLED
VCC
VCC
270R 270R
GND
RI
DTR
CTS
TXDATA
RTS
RXDATA
DSR
DCD
DB9M
SHIELD
10
5
9
4
8
3
7
2
6
1
SHDN
#CBUS0
TXD
RXD
RTS#
CTS#
DTR#
RI#
DCD#
DSR#
27R
27R
GND
47pF
47pF
NOTE: If design uses VCCIO < 3V3 then 10k pullup to VCCIO is required on IO lines
Figure 7.1 Application Example showing USB to RS232 Converter
An example of using the FT231X 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 FT231X to
convert the 3V3 levels of the FT231X 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 ZT3243F which is capable of RS232 communication at up to
1000k baud.
In example shown, the CBUS0 and CBUS1 have been configured as TXLED# and RXLED# and are being
used to drive two LEDs.