FT232RQ R FTDI, Future Technology Devices International Ltd, FT232RQ R Datasheet - Page 29

• Manufacturer Part Number: FT232RQ R
• Description: IC USB TO SERIAL UART 32-QFN
• Manufacturer: FTDI, Future Technology Devices International Ltd
• Series: USBmadeEZ-UARTr

Specifications of FT232RQ R

• Features: USB to UART
• Number Of Channels: 1, UART
• Fifo's: 256 Byte
• Protocol: RS-232, RS-422, RS-485
• Voltage - Supply: 3.3 V ~ 5.25 V
• With Auto Flow Control: Yes
• With Modem Control: Yes
• With Cmos: Yes
• Mounting Type: Surface Mount
• Package / Case: 32-QFN
• For Use With: 768-1023 - MOD USB RS232 DEV/EVAL FT232RL768-1022 - MODULE USB - SERIAL MODULE MINI768-1021 - MODULE MINI DEVELOPMENT FT232RQ768-1019 - MODULE USB-SER UART FT232 24-DIP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 768-1008-2; FT232RQ R

7.3 USB to RS422 Converter
Figure 7.3 USB to RS422 Converter Configuration
An example of using the FT232R as a USB to RS422 converter is shown in Figure 7.3. In this application,
two TTL to RS422 Level Converter ICs are used on the serial UART interface of the FT232R to convert the
TTL levels of the FT232R to RS422 levels. There are many suitable level converter devices available. This
example uses Sipex SP491 devices which have enables on both the transmitter and receiver. Since the
SP491 transmitter enable is active high, it is connected to a CBUS pin in SLEEP# configuration. The
SP491 receiver enable is active low and is therefore connected to a CBUS pin PWREN# configuration. This
ensures that when both the SP491 transmitters and receivers are enabled then the device is active, and
when the device is in USB suspend mode, the SP491 transmitters and receivers are disabled. If a similar
application is used, but the design is USB BUS powered, it may be necessary to use a P-Channel logic
level MOSFET (controlled by PWREN#) in the VCC line of the SP491 devices to ensure that the USB
standby current of 2.5mA is met.
The SP491 is specified to transmit and receive data at a rate of up to 5 Mbaud. In this example the
maximum data rate is limited to 3 Mbaud by the FT232R.
SHIELD
5
1
2
3
4
10nF
100nF
GND
+
Ferrite Bead
Copyright © 2010 Future Technology Devices International Limited
4.7uF +
GND
Vcc
Vcc
100nF
GND
OSCI
USBDM
USBDP
VCCIO
RESET#
NC
OSCO
3V3OUT
VCC
NC
G
N
D
A
G
N
D
FT232R
G
N
D
GND
G
N
D
T
E
S
T
PWREN#
SLEEP#
CBUS0
CBUS1
CBUS2
CBUS4-
CBUS3
DTR#
DSR#
DCD#
RTS#
CTS#
RXD
TXD
RI#
10K
Vcc
FT232R USB UART IC Datasheet Version 2.07
4
5
3
2
5
4
3
2
RS422 LEVEL
6
CONVERTER
RS422 LEVEL
CONVERTER
6
SP491
SP491
Vcc
Vcc
7
7
10
11
12
10
11
12
9
9
120R
120R
Document No.: FT_000053
Clearance No.: FTDI# 38
RXDP
TXDM
TXDP
RXDM
RTSM
RTSP
CTSP
CTSM
RXDM
TXDM
TXDP
RXDP
RTSM
RTSP
CTSP
CTSM
GND
SHIELD
DB9M
29