CDMA and GSM / UMTS Mini Card Hardware Integration Guide
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In the event of a discrepancy in values between this guide and the Product Specification Document (PSD), the PSD takes precedence.
Decouple the VCC line close to the USIM socket. The longer the
trace length (impedance) from socket to module, the greater the
capacitance requirement to meet compliance tests.
EMI / ESD
Investigate sources of localized interference early in the design
cycle.
Methods to mitigate decreased
Rx performance
Provide ESD protection for the USIM connector at the exposed
contact point (in particular, the CLK, VCC, IO, and RESET lines).
Keep very low capacitance traces on the XIM_DATA and
XIM_CLK signals.
To minimize noise leakage, establish a very good ground
connection between the module and host.
Route cables away from noise sources (for example, power
supplies, LCD assemblies, etc.).
Methods to mitigate decreased
Rx performance
Shield high RF-emitting components of the host device (for
example, main processor, parallel bus, etc.).
Methods to mitigate decreased
Rx performance
Use discrete filtering on low frequency lines to filter out unwanted
high-order harmonic energy.
Methods to mitigate decreased
Rx performance
Use multi-layer PCBs to form shielding layers around high-speed
clock traces.
Methods to mitigate decreased
Rx performance
Thermal
Test to worst case operating conditions — temperature, voltage,
and operation mode (transmitter on 100% duty cycle, maximum
power
).
Use appropriate techniques to reduce module temperatures.
(airflow, heat sinks, heat-relief tape, module placement, etc.)
Host / Modem communication
Make sure the host USB driver supports remote wakeup,
resume, and suspend operations, and serial port emulation.
When no valid data is being sent, do not send SOF tokens from
the host (causes unnecessary power consumption).
Table 7-1: Hardware integration design considerations (Continued)
Suggestion
Section where discussed