User Guide

GM47/48 Design Guidelines
BA/SEM/MSC 02:0006 Rev PA1 13
3.4 SIM connections
All track lengths between the SIM card and the module must be kept
below 15cm. This is due to the voltage drop/capacitance associated
with the extra track length and it has type approval issues as it will
affect timing.
This is primarily designed as a 3 Volts SIM interface, but if a 5 Volts
SIM card is connected to it the interface will automatically detect this
and adjust the appropriate parameters.
SIM connections are shown below.
Figure 3.2 SIM Connections
Points to note regarding SIM connection
• The SIM does not need protection between it and the module, if
protection is put in great care must be taken as SIM testing for
type approval is very sensitive to capacitance in the lines.
• De-coupling for Vcc is required, testing has been carried out
using a 2.2uF ceramic capacitor.
• It is recommended that SIM circuitry is run at the opposite end of
the module as a precaution.