Specifications

Smart Machine Smart Decision
SIM7080G _Hardware Design _V1.03 28 2019-12-13
UART1_TXD
UART1_RXD
UART1_RTS
UART1_CTS
UART1_DTR
UART1_DCD
UART1_RI
TXD
RXD
RTS
CTS
DTR
DCD
RING
MODULE (DCE)
CUSTOMER ( DTE)
Serial port
Serial port
Wake up host
Figure 12: UART null modem
Table 10: UART electronic characteristic
Symbol
Description
Min.
Typ.
Max.
Unit
V
IH
UART input high level voltage
1.17
1.8
2.1
V
V
IL
UART input low level voltage
-0.3
0
0.63
V
V
OH
UART output high level voltage
1.35
1.8
1.8
V
V
OL
UART output low level voltage
0
0
0.45
V
The SIM7080G UART is 1.8V voltage interface. If user’s UART application circuit is 3.3V voltage
interface, the level shifter circuits should be used for voltage matching.The following figure
showsthe voltage matching reference design.
TXD
RXD
RTS
CTS
DTR
DCD
RI
A7
A1
A2
A3
A4
A5
A6
MODULE
TXB0108 RGYR
UART
A8
B7
B1
B2
B3
B4
B5
B6
B8
VCCA
OE
VDD_ EXT
100nF
3.3V
100nF
VCCB
GND
TXD_3.3V
RXD_3.3V
RTS_3.3V
CTS_3.3V
DTR_3.3V
DCD_3.3V
RI_3.3V
47K 47K
Figure 13: Reference circuit of level shift
Note: When it uses the level shifter IC, the pullupresistance on TXD_3.3V, RTS_3.3V,
DCD_3.3V and RI_3.3V should not be less than 47KΩ .