User's Manual
Table Of Contents
- Copyright
- Attention
- Trademark
- Versions
- Applicable Model List
- Foreword
- Product Overview
- Structure
- Hardware Introduction
- Hardware Interface
- Electrical and Environmental Characteristic
- RF Interface
L811-EA Module Hardware User Manual Page
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Note:
In order to improve the EMC performance, the SIM card slot should be close to the module as much
as possible.
The filter capacitors for the SIM card signals should be placed close to the SIM card slot as much as
possible.
The ESD devices (e.g. TVS) shall be added to the SIM card signals for ESD protection. They should
be placed close to the SIM card slot as much as possible.
SIM1_CD signal supports hot-plugging. Active high by default (It can be changed to active low by an
AT command). If the module detects the signal with high level, it means a card insertion has detected.
5.7.3 Highlights for USIM Design
The SIM card interface design is very important to have the module and SIM card work normally.
The rules should be followed carefully as below:
SIM card slot and signal routing must keep away from the EMI interference sources, e.g. RF antenna
and digital signals.
The trace length between the module and SIM card should not exceed 100mm.
To avoid crosstalk, USIM_CLK and USIM_IO signals should keep away in case of layout. It’s
recommended to wrap them with ground planes.
SIM card signals should be ESD protected. The ESD devices should have low capacitance (e.g.
Zener diode). It’s recommended to choose ESD devices with capacitance equal or less than 33pF. In
case of layout, ESD devices should be close to the SIM card interface.
5.7.4 USIM Hot-Plugging
The L811-EA module supports the insert detection of the SIM card. With this function, the hot-plugging of
SIM card can be designed.
5.7.4.1 Hardware Connection
The function of SIM card hot-plugging is done by the SIM_CD signal. The SIM1_CD signal is low when
the SIM card is detached, high when the SIM card is inserted.
Note：
For “Normally closed” design, as shown in the figure5-7, the SIM1_CD signal is connected to U2’s
Pin8 (SW2), and Pin7 (SW1) is connected to the ground. When the SIM card is not inserted, SW2
and SW1 are shorted, and SW2 is low. When the SIM card is inserted, SW2 and SW1 are opened,
and the SIM1_CD signal will be pulled high.
For “Normally open” design, as shown in the figure5-8, the SIM1_CD signal is connected to U2’s Pin8