u-blox SARA-G3 Series System Integration Manual page 131

Reference Description
C1, C2, C3, C4 100 nF Capacitor Ceramic X7R 0402 10% 16 V
U1, U2 Unidirectional Voltage Translator
Table 27: Component for UART application circuit with complete V.24 link in DTE/DCE serial communication (3.0 V DTE)
Providing the TXD, RXD, RTS and CTS lines only (not using the complete V.24 link)
If the functionality of the DSR, DCD, RI and DTR lines is not required in, or the lines are not available:
 Connect the module DTR input line to GND, since the module requires DTR active (low electrical
level)

Leave DSR, DCD and RI lines of the module unconnected and floating
If RS-232 compatible signal levels are needed, the Maxim 13234E voltage level translator can be used.
This chip translates voltage levels from 1.8 V (module side) to the RS-232 standard.
If a 1.8 V Application Processor is used, the circuit should be implemented as described in
49Figure 49.
Application Processor
(1.8V DTE)
TxD
RxD
RTS
CTS
DTR
DSR
RI
DCD
GND
Figure 49: 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 is used, appropriate unidirectional voltage translators must be provided
using the module V_INT output as 1.8 V supply, as described in
Application Processor
(3.0V DTE)
Unidirectional
3V0
Voltage Translator
VCC
C1
TxD
RxD
RTS
CTS
U1
DTR
DSR
RI
DCD
GND
Figure 50: UART interface application circuit with partial V.24 link (5-wire) in DTE/DCE serial communication (3.0 V DTE)
UBX-13000995 - R06
SARA-G3 series
(1.8V DCE)
TXD
12
RXD
13
10 RTS
CTS
11
DTR
9
6 DSR
7 RI
DCD
8
GND
SARA-G3 series
(1.8V DCE)
1V8
TP
VCCA VCCB 4 V_INT
C2
DIR1
DIR3
A1 B1 12 TXD
A2 B2 13 RXD
A3 B3 RTS
10
CTS
A4 B4 11
DIR2 OE
DIR4 GND
9 DTR
DSR
6
RI
7
DCD
8
GND
Objective Specification
SARA-G3 series - System Integration Manual
Part Number - Manufacturer
GRM155R61A104KA01 - Murata
SN74AVC4T774 - Texas Instruments
Figure 50Figure 50.
Figure
Design-in
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