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H330S Hardware User Manual
Page 36 of 44
Figure 5- 8 USIM Interface Reference Circuit
Note:
In order to improve EMC performance, the SIM card slot should be close to the module to
the largest extent.
The filter capacitor on the SIM-card signal circuit should be placed close to SIM card pin to
the largest extent.
ESD device (like TVS) shall be added to the SIM-card signal circuit protection. ESD device
should be placed close to SIM card pin.
USIM_IO has been pulled up inside the module. No need to pull it up again from the outside.
USIM_CD signal connection supports hot-plugging; active low. If the module detects the
signal at low level, it means there is a card in the module.
5.6.3 Points for Attention in USIM Design
SIM card interface design is very important for the normal operation of the module and SIM card.
The following points need to be complied with during the design:
SIM card layout and wiring must keep away from EMI interference source, like RF antenna and digital
switch signal.
In order to ensure signal completeness, the wire distance between the module and SIM card should
not exceed 100mm.
In order to avoid mutual interference, USIM_CLK and USIM_IO signals should be separated in wiring.
It would be best to wrap them with ground wire respectively.
SIM card signal line should be protected with ESD. These protective devices should have small
capacitance (like Zener diode, etc.). Users are recommended to select ESD devices with equivalent
capacitance lower than 33pF. During layout, ESD device should be close to the SIM card interface.
5.6.4 USIM Hot-Plugging
H330S supports SIM card status-detection function. This function allows the hot-plugging of SIM card.