User's Manual

GC864 Hardware User Guide

1vv0300733 Rev. 0 - 12/06/06

9 External SIM Holder

Aim of this section is to give basic design guide lines to integrate a SIM holder in applications

that uses Telit modules

9.1 SIM DESIGN GUIDES

In all Telit modules there are five pins for SIM card holder connection

These lines are:

SIMVCC (SIM Power supply )

SIMRST ( SIM Reset )

SIMIO ( SIM Data )

SIMIN ( SIM Presence/Absence )

SIMCLK ( SIM Clock )

SIM connection must take in account of four key issues:

1) Data Integrity: standard rules for digital layout and routing must be followed taking in

consideration that SIMCLK has frequency of 3.57Mhz and SIMIO has 9600Bps baud rate.

2) EMI/EMC: this is a key aspect to consider designing an application based on TELIT module

with internal antenna and/or without a proper-shielded box. Some of these conditions may

occur:

- Antenna picks-up digital noise coming from SIM card lines.

- Antenna radiated field may interfere digital lines.

- Digital lines (in particular clock) may radiate spurious in the surrounding

space.

To overcome all these potential problems, connection lines must be kept as short as

possible and shielded.

SIM-holder position has to be as far as possible from antenna.

RF bypass capacitors (10pF...33pF) closed to SIM card SIM-holder are another good

care.