u-blox LARA-R2 series System Integration Manual page 98

Guidelines for dual SIM card / chip connection
Two SIM card / chip can be connected to the SIM interface of LARA-R2 series modules as described in Figure 47.
LARA-R2 series modules do not support the usage of two SIM at the same time, but two SIM can be populated
on the application board, providing a proper switch to connect only the first or only the second SIM at a time to
the SIM interface of the modules, as described in Figure 47.
LARA-R2 series modules support SIM hot insertion / removal on the GPIO5 pin, to enable / disable SIM interface
upon detection of external SIM card physical insertion / removal: if the feature is enabled using the specific AT
commands (see sections 1.8.2 and 1.12, and u-blox AT Commands Manual [2], +UGPIOC, +UDCONF=50
commands), the switch from first SIM to the second SIM can be properly done when a Low logic level is present
on the GPIO5 pin ("SIM not inserted" = SIM interface not enabled), without the necessity of a module re-boot,
so that the SIM interface will be re-enabled by the module to use the second SIM when a high logic level is re-
applied on the GPIO5 pin.
In the application circuit example represented in Figure 47, the application processor will drive the SIM switch
using its own GPIO to properly select the SIM that is used by the module. Another GPIO may be used to handle
the SIM hot insertion / removal function of LARA-R2 series modules, which can also be handled by other external
circuits or by the cellular module GPIO according to the application requirements.
The dual SIM connection circuit described in Figure 47 can be implemented for SIM chips as well, providing
proper connection between SIM switch and SIM chip as described in Figure 45.
If it is required to switch between more than 2 SIM, a circuit similar to the one described in Figure 47 can be
implemented: in case of 4 SIM circuit, using proper 4-throw switch instead of the suggested 2-throw switches.
Follow these guidelines connecting the module to two SIM connectors:

Use a proper low on resistance (i.e. few ohms) and low on capacitance (i.e. few pF) 2-throw analog switch
(e.g. Fairchild FSA2567) as SIM switch to ensure high-speed data transfer according to SIM requirements.

Connect the contacts C1 (VCC) of the two UICC / SIM to the VSIM pin of the module by means of a proper
2-throw analog switch (e.g. Fairchild FSA2567).

Connect the contact C7 (I/O) of the two UICC / SIM to the SIM_IO pin of the module by means of a proper
2-throw analog switch (e.g. Fairchild FSA2567).

Connect the contact C3 (CLK) of the two UICC / SIM to the SIM_CLK pin of the module by means of a
proper 2-throw analog switch (e.g. Fairchild FSA2567).

Connect the contact C2 (RST) of the two UICC / SIM to the SIM_RST pin of the module by means of a
proper 2-throw analog switch (e.g. Fairchild FSA2567).

Connect the contact C5 (GND) of the two UICC / SIM to ground.

Provide a 100 nF bypass capacitor (e.g. Murata GRM155R71C104K) at the SIM supply line (VSIM), close to
the related pad of the two SIM connectors, to prevent digital noise.

Provide a bypass capacitor of about 22 pF to 47 pF (e.g. Murata GRM1555C1H470J) on each SIM line
(VSIM, SIM_CLK, SIM_IO, SIM_RST), very close to each related pad of the two SIM connectors, to prevent
RF coupling especially in case the RF antenna is placed closer than 10 - 30 cm from the SIM card holders.

Provide a very low capacitance (i.e. less than 10 pF) ESD protection (e.g. Tyco Electronics PESD0402-140) on
each externally accessible SIM line, close to each related pad of the two SIM connectors, according to the
EMC/ESD requirements of the custom application.

Limit capacitance and series resistance on each SIM signal to match the SIM specifications requirements
(27.7 ns = max allowed rise time on SIM_CLK, 1.0 µs = max allowed rise time on SIM_IO and SIM_RST).
UBX-16010573 - R02
LARA-R2 series - System Integration Manual
Objective Specification Design-in
Page 98 of 148