DE910 Series Hardware User Guide
1vv0300951 Rev.9 – 2015-05-11
Reproduction forbidden without written authorization from Telit Communications S.p.A. - All Rights
Reserved. Page 49 of 77
Actually, the RS232 UART 16450, 16550, 16650 & 16750 chipsets accept signals with lower
levels on the RS232 side (EIA/TIA-562), allowing a lower voltage-multiplying ratio on the
level translator. Note that the negative signal voltage must be less than 0V and hence some
sort of level translation is always required.
The simplest way to translate the levels and invert the signal is by using a single chip level
translator. There are a multitude of them, differing in the number of drivers and receivers and
in the levels (be sure to get a true RS232 level translator not a RS485 or other standards).
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.
In order to translate the whole set of control lines of the UART you will need:
5 drivers
3 receivers
An example of RS232 level adaption circuitry could be accomplished using 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).
NOTE:
In this case the length of the lines on the application has to be taken into account to avoid
problems in case of High-speed rates on RS232.
