User's Manual

LE920 Hardware User Guide
1vv0301026 Rev.8 2015-01-03
Reproduction forbidden without written authorization from Telit Communications S.p.A. - All Rights
Reserved. Page 79 of 88
 For external SIM configuration only, leave E8 open (or set to GND) and follow 15.3.1
section guidelines.
 For configuration with both internal eSIM and external SIM cards use following
approach:
1) Both eSIM and external SIM share the same lines except SIMRST1 and SIMIN1
lines that should be switched between them, either electronically or manually. For
SIMRST1 switching, it is mandatory to keep second output of SW1 in high Z state
when connected to the first one, therefore analog relay (for example DG9431
Single SPDT Analog Switch) / mechanical relay / 3 state buffer with separate
enable for each output is recommended.
2) Connect 200kΩ pulldown resistor (R2) to external SIM Reset line for keeping
external SIM in high Z state during internal eSIM use, whenever SIMRST1 signal
routed to E8 ESIM_RST path. This method prevents interference between the SIM
cards enabling only one of them by SW1 selection.
3) For SIMIN1 card detection mechanism, similar approach to SIMRST1
recommended. Manual selection with 0Ω resistors is another option.
NOTE FOR R1:
The resistor value on SIMIO pulled up to SIMVCC should be defined accordingly in order to
be compliant with 3GPP specification.
LE920-NA AUTO S contains an internal pull-up resistor on SIMIO1.
However, the un-mounted option in the application design can be recommended in order to
tune R1 if necessary.
C1
R2
Not mounted
R1
B11
A10
SIMCLK1
SIMRST1
SIMVCC1
LE920-NA AUTO S module
SIMIN1
8
7
SIMIN
1
2
3
4
5
ESIM_RST
A8
E8
SIMIO1
6
External SIM card
SPDT switch 1
SPDT switch 2
SW1
SW2
8.2K
GND
GND
GND
GND
200k
GND
B9
B7
C2
C3
C4
100nF
33pF
33pF
33pF