Sierra Wireless WISMO218 - Manual (Page 44)

WA_DEV_W218_PTS_002 Rev 005 Page 44 of 109
Product Technical Specification &
Customer Design Guidelines
SIM Interface
The Subscriber Identification Module can be directly connected to the WISMO218 through this
dedicated interface.
Features
The SIM interface controls both 1.8V and 3V SIM cards.
It is recommended to add Transient Voltage Suppressor diodes (TVS) on the signal connected to the
SIM socket in order to prevent any Electrostatic Discharge.
TVS diodes with low capacitance (less than 10pF) have to be connected on SIM-CLK and SIM-IO
signals to avoid any disturbance from the rising and falling edge.
These types of diodes are mandatory for the Full Type Approval. They will be placed as close as
possible to the SIM socket.
The recommended low capacitance diode array to use is the DALC208SC6 from ST Microelectronics.
The SIM uses four (4) signals, namely:

SIM-VCC: SIM power supply

~SIM-RST: reset

SIM-CLK: clock

SIM-IO: I/O port
The SIM interface controls a 3V/1V8 SIM. This interface is fully compliant with the GSM 11.11
recommendations concerning SIM functions.