N723-EA Hardware User Guide
Chapter 5 Application Interfaces
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43
Figure 5-21
Recommended level shifting circuit 2
UART_TXD
VDD_1P8
10k
Ω
R3
Q1
4.7k
Ω
R1
22k
Ω
R2
10k
Ω
R4
10pF
C1
10pF
C2
100k
Ω
R5
Q2
4.7k
Ω
R6
VCC_IO
MCU_RXD
MCU_TXD
VDD_1P8
Q4
10k
Ω
R10
10k
Ω
R9
10pF
C4
10pF
C3
Q3
UART_RXD
100k
Ω
R12
100k
Ω
R11
10k
Ω
R8
4.7k
Ω
R7
PCB design guideline:
−
Q1/Q2: MMBT3904 or MMBT2222 High-speed transistors are better.
−
MCU_TXD and MCU_RXD are the sending and receiving ports of the MCU respectively,
and TXD and RXD are the sending and receiving ports of the module respectively. VCC_IO
is the IO voltage of the MCU. VDD_1P8 is the IO voltage of the module.
⚫
If the serial port baud rate is less than or equal to 115200 bps, designing the CTS and RTS
circuit by referring to recommended level shifting circuit 3 is recommended. As shown in Figure
5-22.