Uart Application - Quectel BC950N-N1 Hardware Design

3.8.5. UART Application

The module provides 3.0V UART interfaces. A level translator should be used if the application is
equipped with a 3.3V UART interface. A level translator TXS0108EPWR provided by Texas Instruments
(please visit http://www.ti.com for more information) is recommended. The following figure shows a
reference design.
Module
VDD_EXT
RXD
TXD
RXD_DBG
TXD_DBG
RXD_AUX
TXD_AUX
RI
GND
Figure 19: Reference Circuit with Voltage Level Translator Chip
Another example with transistor translation circuit is shown as below. The circuit design of dotted line
section can refer to the design of solid line section, in terms of both module input and output circuit
designs, but please pay attention to the direction of connection.
BC950N-N1_Hardware_Design
VCCA
0.1uF
OE
A1
A2
A3
A4
A5
A6
A7
51K
A8
VDD_EXT
Module
10K
RXD
TXD
VDD_EXT
RXD_DBG
TXD_DBG
RXD_AUX
TXD_AUX
RI
GND
Figure 20: Reference Circuit with Transistor Circuit
VCCB
0.1uF
GND
B1
B2
Translator
B3
B4
B5
B6
B7
51K
B8
4.7K
VDD_EXT
1nF
TXD
1nF
10K
4.7K VCC_DTE
TXD_DBG
RXD_DBG
TXD_AUX
RXD_AUX
GPIO
LPWA Module Series
BC950N-N1 Hardware Design
DTE
VDD
TXD
RXD
TXD_DBG
RXD_DBG
TXD_AUX
RXD_AUX
GPIO
GND
DTE
RXD
GND
32 / 59