User's Guide

LE910Cx HW User Guide
Doc#: 1VV0301298
Rev. 13.0 Page 73 of 124 2019-07-15
By convention, the driver is the level translator from the 0-1.8V UART to the RS232 level.
The receiver is the translator from the RS232 level to 0-1.8V UART. To translate the
whole set of control lines of the UART, the following is required:
• 2 drivers
• 2 receivers
WARNING:
The digital input lines, operating at 1.8V CMOS levels, have absolute
maximum input voltage of 2.0V. The level translator IC outputs on the
module side (i.e. LE910Cx inputs) will cause damage to the module inputs if
the level translator is powered with +3.8V power.
So, the level translator IC must be powered from a dedicated +1.8V power
supply.
As an example, RS232 level adaption circuitry could use a MAXIM transceiver (MAX218).
In this case, the chipset is capable of translating directly from 1.8V to the RS232 levels
(example on 4 signals only).
Figure 13: RS232 Level Adaption Circuitry Example
NOTE:
In this case, the length of the lines on the application must be taken into
account to avoid problems in the case of high-speed rates on RS232.
The RS232 serial port lines are usually connected to a DB9 connector as shown in Figure
14. Signal names and directions are named and defined from the DTE point of view.
Figure 14: RS232 Serial Port Lines Connection Layout