Quectel BC66-NA Manual page 31

Module
VDD_EXT
RXD
TXD
RXD_DBG
TXD_DBG
RXD_AUX
TXD_AUX
RI
GND
Figure 18: 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.
The following circuit shows a reference design for the communication between the module and a PC with
standard RS-232 interface. Please make sure the I/O voltage of level shifter which connects to module is
1.8V.
BC66-NA_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 19: Reference Circuit with Transistor Circuit
VCCB
0.1uF
GND
B1
B2
Translator
B3
B4
B5
B6
B7
51K
B8
4.7K
VDD_EXT
1nF
1nF
10K
VCC_DTE
4.7K
NB-IoT Module Series
BC66-NA Hardware Design
DTE
VDD
TXD
RXD
TXD_DBG
RXD_DBG
TXD_AUX
RXD_AUX
GPIO
GND
DTE
TXD
RXD
TXD_DBG
RXD_DBG
TXD_AUX
RXD_AUX
GPIO
GND
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