FT230XQ-R International Semiconductor Technologies, FT230XQ-R Datasheet - Page 27

• Manufacturer Part Number: FT230XQ-R
• Description: Specifications: Number of Channels: 1, UART ; Lead Free Status: Lead Free ; RoHS Status: RoHS Compliant
• Manufacturer: International Semiconductor Technologies

7.3 USB to RS422 Converter
Figure 7.3 USB to RS422 Converter Configuration
An example of using the FT230X 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 FT230X to convert the
TTL levels of the FT230X to RS422 levels. There are many suitable level converter devices available. This
example uses Zywyn ZT3491 devices which have enables on both the transmitter and receiver. Since the
ZT3491 transmitter enable is active high, it is connected to a CBUS pin in SLEEP# configuration. The
ZT3491 receiver enable is active low and is therefore connected to a CBUS pin PWREN# configuration.
This ensures that when both the ZT3491 transmitters and receivers are enabled then the device is active,
and when the device is in USB suspend mode, the ZT3491 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 ZT3491 devices to ensure that the USB
standby current of 2.5mA is met.
The ZT3491 is specified to transmit and receive data at a rate of up to 16 Mbaud. In this example the
maximum data rate is limited to 3 Mbaud by the FT230X.
SHIELD
5
1
2
3
4
100nF
GND
Copyright © 2013 Future Technology Devices International Limited
10nF
47pF
Ferrite
Bead
VCC
GND
+
GND
4.7uF
RXD
TXD
RTS
CTS
VCC
47pF
GND
27R
27R
100nF
USBDM
VCC
USBDP
3V3OUT
RESET#
VCCIO
VCCIO
FT230X
PWREN#
SLEEP#
RTS#
CTS#
RXD
TXD
10K
Vcc
Document No.: FT_000566 Clearance No.: FTDI# 260
FT230X USB TO BASIC UART IC
4
5
3
2
5
4
3
2
RS 422 LEVEL
6
RS 422 LEVEL
6
CONVERTER
CONVERTER
TXDM
RXDM
TXDP
RXDP
RTSM
RTSP
CTSP
CTSM
ZT3491
ZT3491
Vcc
Vcc
7
7
GND
SHIELD
10
11
12
10
11
12
9
9
Version 1.2
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