Xplore Technologies Corp. MC7750 Manual Do Utilizador
Product Technical Specification & Customer Design Guidelines
32
Proprietary and Confidential - Contents subject to change
2400074
SIM implementation
Note: For interface design
requirements, refer to:
requirements, refer to:
(2G) 3GPP TS 51.010-1,
section 27.17, or
section 27.17, or
(3G) ETSI TS 102 230
V5.5.0, section 5.2.
V5.5.0, section 5.2.
When designing the remote SIM interface, you must make sure that SIM signal
integrity is not compromised.
integrity is not compromised.
Some design recommendations include:
•
Total impedance of the VCC and GND connections to the SIM, measured at
the module connector, should be less than 1
the module connector, should be less than 1
to minimize voltage drop
(includes any trace impedance and lumped element components — inductors,
filters, etc.).
filters, etc.).
•
Position the SIM connector
10 cm from the module. If a longer distance is
required because of the host device design, use a shielded wire assembly —
connect one end as close as possible to the SIM connector and the other end
as close as possible to the module connector. The shielded assembly may
help shield the SIM interface from system noise.
connect one end as close as possible to the SIM connector and the other end
as close as possible to the module connector. The shielded assembly may
help shield the SIM interface from system noise.
•
Reduce crosstalk on the USIM_DATA line to reduce the risk of failures during
GCF approval testing.
GCF approval testing.
•
Avoid routing the USIM_CLK and USIM_DATA lines in parallel over distances
2 cm — cross-coupling of these lines can cause failures.
•
3GPP has stringent requirements for I / O rise time (<1 µs), signal level limits,
and noise immunity — consider this carefully when developing your PCB
layout.
· Keep signal rise time <1 µs — keep USIM signals as short as possible, and
and noise immunity — consider this carefully when developing your PCB
layout.
· Keep signal rise time <1 µs — keep USIM signals as short as possible, and
keep very low capacitance traces on the USIM_DATA and USIM_CLK
signals. High capacitance increases signal rise time, potentially causing
your device to fail certification tests.
signals. High capacitance increases signal rise time, potentially causing
your device to fail certification tests.
•
Add external pull-up resistors (15 k
–30 k), if required, between the
USIM_DATA and USIM_PWR lines to optimize the signal rise time.
•
VCC line should be decoupled close to the SIM socket.
•
SIM is specified to run up to 5 MHz (SIM clock rate). Take note of this speed
in the placement and routing of the SIM signals and connectors.
in the placement and routing of the SIM signals and connectors.
•
You must decide whether additional ESD protection is required for your
product, as it is dependent on the application, mechanical enclosure, and SIM
connector design. The SIM pins will require additional ESD protection if they
are exposed to high ESD levels (i.e. can be touched by a user).
product, as it is dependent on the application, mechanical enclosure, and SIM
connector design. The SIM pins will require additional ESD protection if they
are exposed to high ESD levels (i.e. can be touched by a user).
•
Putting an optional decoupling capacitor at USIM_PWR near the SIM socket
is recommended — the longer the trace length (impedance) from the socket to
the module, the greater the capacitance requirement to meet compliance
tests.
is recommended — the longer the trace length (impedance) from the socket to
the module, the greater the capacitance requirement to meet compliance
tests.
•
Putting an optional series capacitor and resistor termination (to ground) at
USIM_CLK at the SIM socket to reduce EMI and increase signal integrity is
recommended if the trace length between the SIM socket and module is
long — 47 pF and 50
USIM_CLK at the SIM socket to reduce EMI and increase signal integrity is
recommended if the trace length between the SIM socket and module is
long — 47 pF and 50
resistor are recommended.
•
Test your first prototype host hardware with a Comprion IT
3
SIM test device at
a suitable testing facility.