Telit Wireless Solutions LN930 - (U)SIM Interface and Recommendations

LN930 M.2 Hardware User Guide
1VV0301078 Rev.10 – 2015-11-11
Reproduction forbidden without written authorization from Telit Communications S.p.A. - All Rights Reserved. Page 29 of 88
3.2
(U)SIM Interface
The USIM interface is compatible with the ISO 7816-3 IC Card standard on the issues
required by the GSM 11.12 and GSM 11.18 standard.
Both 1.8 V and 3 V SIM Cards are supported.
A few comments on the SIM_DETECT signal
1. An external pull-up resistor is connected to SIM_DETECT on the WWAN M.2
module.
2. When a SIM is inserted, SIM_DETECT will be high.
3. When a SIM is removed or not present, SIM_DETECT will be low.
4. The host does not need to drive this signal. It can be tri-stated.
Table 7
(U)SIM Interface Signals
Signal Name
Description
Pin
Direction
(WWAN)
Voltage
Level
UIM_CLK
Clock SIM Card
32
O
1.8 V/3.0
V
UIM_DATA
Input/ Output SIM Card
34
I, O
1.8 V/3.0
V
UIM_RESET
Reset signal for SIM card
30
O
1.8 V/3.0
V
USIM_PWR
1.8 V/3 V Supply for SIM Card
36
O
1.8 V/3.0
V
SIM Detect
SIM Card Detection
66
I
1.8 V
3.2.1
SIM Design Recommendations
The following design guidelines are recommended for the SIM card socket mounted on the
host system:
• Length of the traces UIM_CLK, UIM_DATA, and UIM_RESET should not exceed
10 cm.
• UIM_DATA is a sensitive open-drain bi-directional signal. It should not be mounted
beside the UIM_CLK signal for long distances. It is recommended to place the
UIM_RST trace between UIM_DATA and UIM_CLK to provide isolation. If the
traces are run a long distance, surround the UIM_DATA with ground to shield from
system noise and UIM_CLK.
• The rise time for UIM_DATA should not exceed 1 µs per the 3GPP specification.
High input capacitance may increase rise time and lead to certification failure.
o Keep UIM traces with low capacitance between each other and to GND
o An ESD component with high capacitance may increase rise time.