Specifications

SIM7912&SIM7906 Hardware Design V1.02
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chip needs to be added in the middle. It is recommended to use TI’s TXS0104EPWR level shift, the
reference circuit is as follows.
VCCA
TXS0104EPWR
100pF
OE
A1
A2
A3
A4
VCCB
GND
B1
B2
B3
B4
VDD_1V8
UART_CTS
UART_RTS
UART_TXD
UART_RXD
100pF
VDD_3V3
UART_CTS_3V3
UART_RTS_3V3
UART_TXD_3V3
UART_RXD_3.3V
Figure 23: UART level conversion circuit
The following level shifting circuits can also be used:
VDD_1V8
4.7K
47K
TXD
4.7K
Module
VDD_EXT
RXD
VDD
DTE
Figure 24: UART TX level conversion circuit
VDD_1V8
4.7K
47K
4.7K
DTE
RXD
Module
VDD_1V8
TXD
VDD
Figure 25: UART RX level conversion circuit