N58 Hardware User Guide
Chapter 5 Application Interfaces
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46
Figure 5-22 Recommended level shifting circuit 3
UART_RTS
VDD_1P8
VCC_IO
4.7 k
Ω
10 k
Ω
Q1
R2
R3
MCU_CTS
MCU_RTS
VDD_1P8
VDD_1P8
4.7 k
Ω
10 k
Ω
Q2
R4
R1
UART_CTS
Related components:
R2/R4: 2 kΩ to 10 kΩ. The higher the working rate of the UART interface, the smaller the value
of R2/R4.
R1/R3: 4.7 kΩ to 10 kΩ. The higher the working rate of the UART interface, the smaller the value
of R1/R3.
Q1/Q2: MMBT3904 or MMBT2222. High-rate transistors are better.
5.3.3 USIM
Pin Name
Pin No.
I/O
Function
Remarks
USIM1_VCC
35
PO
USIM1 power output
Adaptive 1.8 V/3.0 V.
USIM1_DATA
36
B
USIM1
data
input/output
Connect this pin to USIM1_VCC by
using a 4.7 kΩ pull-up resistor.
USIM1_CLK
37
DO
USIM1 clock output
-
USIM1_RESET
38
DO
USIM1 reset
-
USIM1_DET
39
DI
USIM1 detection
-
USIM2_VCC
21
PO
USIM2 power output
Adaptive 1.8 V/3V.