User Guide

GM47/48 Design Guidelines
BA/SEM/MSC 02:0006 Rev PA1 17
3.7 Interfacing to a 3.3V µProcessor
Although the inputs to the modules can withstand a certain degree of
over voltage they should not be purposefully driven at a higher voltage
than that quoted in the pin out in appendix II.
This particularly applies to the serial com ports used to send and
receive the commands to and from the module. Level shifting I/C’s are
required to interface to the module.
An example of a suitable device is a Max3372 for level shifting, please
follow the below link for the data sheet. Note : ESD protection is not a
requirement for the level shifter.
http://pdfserv.maxim-ic.com/arpdf/MAX3372E-MAX3393E.pdf
3.8 Software download and logging circuitry
Below the circuitry is shown which allows software download and
logging to be performed.
VCC 3V6
MAX3380E
VIO 2V7
CTMS
CFMS
VCC
0.1uF
1,3,5,7,9,11
2,4,6,8,10,12
34
58
45
46
SERVICE
14
0.1uF
ON/OFF
3
2
5
TD
RD
DTE
9 pin
D-Type
0.1uF
0.1uF
0.1uF
0.1uF
V
L
Fon
Foff
R1OUT
R1IN
T1IN
T1OUT
GND
V+
V-
+
+
+
+
C1+
C1-
C2+
C2-
15
19 13 20
17
5
11
4
8
12
3
2 18 6
1
GM47 SYSTEM CONNECTOR
9
T2IN
R2IN
14
The data sheet for the Maxim device can be found at
http://pdfserv.maxim-ic.com/arpdf/MAX3380E-MAX3381E.pdf