LISA-U series - System Integration Manual
UBX-13001118 - R17
Advance information
System description
Page 70 of 190
1.9.2.4
UART application circuits
Providing the full RS-232 functionality (using the complete V.24 link)
If RS-232 compatible signal levels are needed, to provide full RS-232 (9 lines) functionality two different external
voltage translators (e.g. Maxim MAX3237E and Texas Instruments SN74AVC4T774) can be used. The Texas
Instruments chips provide the translation from 1.8 V to 3.3 V, while the Maxim chip provides the translation
from 3.3 V to RS-232 compatible signal level.
If a 1.8V application processor is used, for complete RS-232 functionality conforming to
ITU Recommendation
in DTE/DCE serial communication, the complete UART interface of the module (DCE) must be connected to a
1.8V DTE as described in Figure 32.
TxD
Application Processor
(1.8V DTE)
RxD
RTS
CTS
DTR
DSR
RI
DCD
GND
LISA-U series
(1.8V DCE)
15
TXD
12
DTR
16
RXD
13
RTS
14
CTS
9
DSR
10
RI
11
DCD
GND
0
Ω
0
Ω
TP
TP
0
Ω
0
Ω
TP
TP
Figure 32: UART interface application circuit with complete V.24 link in DTE/DCE serial communication (1.8V DTE)
If a 3.0 V Application Processor is used, appropriate unidirectional voltage translators must be provided using the
module
V_INT
output as 1.8 V supply, as described in Figure 33.
4
V_INT
TxD
Application Processor
(3.0V DTE)
RxD
RTS
CTS
DTR
DSR
RI
DCD
GND
LISA-U series
(1.8V DCE)
15
TXD
12
DTR
16
RXD
13
RTS
14
CTS
9
DSR
10
RI
11
DCD
GND
0
Ω
0
Ω
TP
TP
0
Ω
0
Ω
TP
TP
1V8
B1
A1
GND
U1
B3
A3
VCCB
VCCA
Unidirectional
Voltage Translator
C1
C2
3V0
DIR3
DIR2
OE
DIR1
VCC
B2
A2
B4
A4
DIR4
1V8
B1
A1
GND
U2
B3
A3
VCCB
VCCA
Unidirectional
Voltage Translator
C3
C4
3V0
DIR1
DIR3
OE
B2
A2
B4
A4
DIR4
DIR2
Figure 33: UART interface application circuit with complete V.24 link in DTE/DCE serial communication (3.0 V DTE)
Reference
Description
Part Number - Manufacturer
C1, C2, C3, C4
100 nF Capacitor Ceramic X7R 0402 10% 16 V
GRM155R61A104KA01 - Murata
U1, U2
Unidirectional Voltage Translator
SN74AVC4T774 - Texas Instruments
Table 30: Component for UART application circuit with complete V.24 link in DTE/DCE serial communication (3.0 V DTE)