TOBY-L2 and MPCI-L2 series - System Integration Manual
UBX-13004618 - R07
Advance Information
Design-in
Page 102 of 158
Guidelines for dual SIM card / chip connection
Two SIM card / chip can be connected to the SIM interface of TOBY-L2 and MPCI-L2 series modules as described
in the application circuits of Figure 52.
TOBY-L2 and MPCI-L2 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 52.
TOBY-L2 “00”, “01”, and “50” product versions and MPCI-L2 modules do not support SIM hot insertion /
removal functionality: the physical connection between the external SIM and the module has to be provided
before the module boot and then held for normal operation. Switching from one SIM to another can only be
properly done within one of these two time periods:
after module switch-off by the AT+CPWROFF and before module switch-on by
PWR_ON
after network deregistration by AT+COPS=2 and before module reset by AT+CFUN=16
TOBY-L2 modules (except “00”, “01”, “50” product versions) support SIM hot insertion / removal on the
GPIO5
pin: if the feature is enabled using the specific AT commands (see sections 1.8.2 and 1.11, and
u-blox AT
Commands Manual
[3], +UGPIOC, +UDCONF 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 52, 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 TOBY-L2 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 52 can be implemented for SIM chips as well, providing
proper connection between SIM switch and SIM chip as described in Figure 50.
If it is required to switch between more than 2 SIM, a circuit similar to the one described in Figure 52 can be
implemented: in case of 4 SIM circuit, using proper 4-throw switch instead of the suggested 2-throw switches.
Follow these guidelines to connect the module to two external 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) and C6 (VPP) of the two UICC / SIM to the
VSIM
/
UIM_PWR
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
/
UIM_DATA
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
/
UIM_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
/
UIM_RESET
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 (
VSIM
/
UIM_PWR
),
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, 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 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 requirements (27.7 ns is the
maximum allowed rise time on clock line, 1.0 µs is the maximum allowed rise time on data and reset lines).
