User's Manual

LTE Module Series
EC25Hardware Design
EC25_Hardware_DesignConfidential / Released 44 / 90
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 a reference design.
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. Thecircuit design of dotted line
section can refer to the design of solid line section, in terms of both module input and output circuit
designs, but please pay attention to the direction of connection.