Rainbow Electronics GM862-QUAD-PY - Manual (Page 34)

GM862-QUAD / PY Hardware User Guide
1vv0300748 Rev. 5 - 20/09/07
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights Reserved page 34 of 68
7.2 5V UART level translation
If the OEM application uses a microcontroller with a serial port (UART) that works at a voltage different
from 2.8 - 3V, then a circuitry has to be provided to adapt the different levels of the two set of signals.
As for the RS232 translation there are a multitude of single chip translators. For example a possible
translator circuit for a 5V TRANSMITTER/RECEIVER can be:
TIP: This logic IC for the level translator and 2.8V pull-ups (not the 5V one) can be powered directly from PWRMON
line of the GM862-QUAD / PY. Note that the TC7SZ07AE has open drain output, therefore the resistor R2 is
mandatory.