LTE Module Series
EC25-V User Manual
EC25-V_User_Manual Confidential / Released 37 /
69
Table 13: Logic Levels of Digital I/O
Parameter
Min.
Max.
Unit
V
IL
-0.3
0.6
V
V
IH
1.2
2.0
V
V
OL
0
0.45
V
V
OH
1.35
1.8
V
The module provides 1.8V UART interface. A level translator should be used if your application is
equipped with a 3.3V UART interface. A level translator TXS0108EPWR provided by
Texas Instrument
is
recommended. The following figure shows the reference design.
VCCA
VCCB
OE
A1
A2
A3
A4
A5
A6
A7
A8
GND
B1
B2
B3
B4
B5
B6
B7
B8
VDD_EXT
RI
DCD
RTS
RXD
DTR
CTS
TXD
51K
51K
0.1uF
0.1uF
RI_MCU
DCD_MCU
RTS_MCU
RXD_MCU
DTR_MCU
CTS_MCU
TXD_MCU
VDD_MCU
Translator
Figure 20: Reference Circuit with Translator Chip
Please visit http://www.ti.com for more information.
Another example with transistor translation circuit is shown as below. The circuit of dotted line can refer to
the circuit of solid line. Please pay attention to the direction of connection. Input dotted line of the module
should refer to input solid line of the module. Output dotted line of the module should refer to output solid
line of the module.