Ublox SARA-G450 Series User Manual

SARA-G450 - System integration manual
UBX-18046432 - R08 Design-in Page 93 of 143
C1-Public
If a 3.0 V application processor (DTE) is used and module (DCE) generic digital interfaces are
configured to operate at 3.0 V (V_INT = 3 V, if VSEL pin is left unconnected; see 1.5.3), the circuit
should be implemented as described in Figure 51, given that the DTE will behave properly regardless
of the DSR input setting.
TxD
Application Processor
(3.0V DTE)
RxD
RTS
CTS
DTR
DSR
RI
DCD
GND
SARA-G450
(3.0V 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
21
VSEL
Figure 51: UART application circuit with partial V.24 link (6-wire) in the DTE/DCE serial interface (3.0 V DTE / 3.0 V DCE)
If a 3.0 V application processor (DTE) is used and module (DCE) generic digital interfaces are
configured to operate at 1.8 V (V_INT = 1.8 V, if VSEL pin is connected to GND; see 1.5.3), 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 the 1.8 V supply for the voltage
translators on the module side, as described in Figure 52, given that the DTE will behave properly
regardless of the DSR input setting.
4
V_INT
TxD
Application Processor
(3.0V DTE)
RxD
RTS
CTS
DTR
DSR
RI
DCD
GND
SARA-G450
(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
B3A3
VCCB
VCCA
Unidirectional
voltage translator
C1
C2
3V0
DIR3
DIR2 OE
DIR1
VCC
B2 A2
B4A4
DIR4
1V8
B1 A1
GND
U2
VCCB
VCCA
Unidirectional
voltage translator
C3
3V0
DIR1
OE
B2 A2
DIR2
C4
21
VSEL
Figure 52: UART application circuit with partial V.24 link (6-wire) in the DTE/DCE serial interface (3.0 V DTE / 1.8 V DCE)
Reference
Description
Part number – Manufacturer
C1, C2, C3, C4
100 nF capacitor ceramic X7R 0402 10% 16 V
GRM155R61A104KA01 – Murata
U1
Unidirectional voltage translator
SN74AVC4T774
15
- Texas Instruments
U2
Unidirectional voltage translator
SN74AVC2T245
15
– Texas Instruments
Table 33: Parts for UART application circuit with partial V.24 link (6-wire) in DTE/DCE serial interface (3.0 V DTE / 1.8 V DCE)
15
Voltage translator providing partial power-down feature so that the DTE 3.0 V supply can be also ramped up before V_INT
1.8 V supply

Ublox SARA-G450 Series Specifications

General

Brand	Ublox
Model	SARA-G450 Series
Category	GSM/GPRS Modules
Language	English