User's Guide

HE863 Family Hardware User Guide
1vv0300891 Rev.5
- 2011-03-18
Reproduction forbidden without Telit Communications S.p.A’s. written authorization - All Rights
Reserved. Page 84 of 89
NOTE:
SIMIN doesn’t require any pull-up resistor. It is built in.
SIM card is detected inserted when this line is short to
ground.(TBD)
If in the application the SIM holder doesn’t foresee the
switch for the presence/absence of the SIM card, the SIMIN
line must be connected to ground.
15.2. SIM interface
When designing SIM interface on the application boards, the
following schematics are recommended.
3GPP specifications define that the rise time and the fall
time of the IO signal shall not exceed 1 usec.
R1 and C2 are very closely related to the rise and fall time
of the SIMIO signal.
It can differ according to application board therefore it
should be considered at the customer point of view.
It means that the values of R1,C1,C2,C3,C4,C5 may be necessary
to be optimized according to the application design.