SARA-R4/N4 series - System Integration Manual
UBX-16029218 - R11
Design-in
Page 101 of 157
TxD
Applicat ion Processor
(1.8V DTE)
RxD
RTS
CTS
DTR
DSR
RI
DCD
GND
SARA-R4/ N4
(1.8V DCE)
12
TXD
9
DTR
13
RXD
10
RTS
11
CTS
6
DSR
7
RI
8
DCD
GND
0
Ω
TP
0
Ω
TP
0
Ω
TP
0
Ω
TP
Figure 44: UART interface application circuit with partial V.24 link (5-wire) in the DTE/DCE serial communication (1.8V DTE)
If a 3.0 V Application Processor (DTE) is used, then it is recommended to connect the 1.8 V UART interface
of the module (DCE) by means of appropriate unidirectional voltage translators using the module
V_INT
output as 1.8 V supply for the voltage translators on the module side, as in
4
V_INT
TxD
Applicat ion Processor
(3.0 V DTE)
RxD
RTS
CTS
DTR
DSR
RI
DCD
GND
SARA-R4/ N4
(1.8V DCE)
12
TXD
9
DTR
13
RXD
10
RTS
11
CTS
6
DSR
7
RI
8
DCD
GND
1V8
B1
A1
GND
U1
B3
A3
VCCB
VCCA
Unidirect ional
Volt age Translat or
C1
C2
3V0
DIR3
DIR2
OE
DIR1
VCC
B2
A2
B4
A4
DIR4
TP
0
Ω
TP
0
Ω
TP
0
Ω
TP
TP
Figure 45: UART interface application circuit with a partial V.24 link (5-wire) in DTE/DCE serial communication (3.0 V DTE)
Reference
Description
Part Number - Manufacturer
C1, C2
100 nF Capacitor Ceramic X7R 0402 10% 16 V
GRM155R61A104KA01 - Murata
U1
Unidirectional Voltage Translator
SN74AVC4T774
17
- Texas Instruments
Table 31: UART application circuit components with a partial V.24 link (5-wire) in DTE/DCE serial communication (3.0 V DTE)
17
Voltage translator providing partial power down feature so that the DTE 3 V supply can be also ramped up before
V_INT
1.8 V supply