Sierra Wireless MC5725 Hardware Integration Manual page 76

CDMA and GSM / UMTS Mini Card Hardware Integration Guide
Table 7-1: Hardware integration design considerations (Continued)
Suggestion
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.
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.).
Shield high RF-emitting components of the host device (for
example, main processor, parallel bus, etc.).
Use discrete filtering on low frequency lines to filter out unwanted
high-order harmonic energy.
Use multi-layer PCBs to form shielding layers around high-speed
clock traces.
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).
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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.
Proprietary and Confidential
Section where discussed
USIM operation
page 67
Methods to mitigate decreased
Rx performance
page 42
USIM operation
page 67
Ground connection
page 39
Methods to mitigate decreased
Rx performance
page 42
Methods to mitigate decreased
Rx performance
page 42
Methods to mitigate decreased
Rx performance
page 42
Methods to mitigate decreased
Rx performance
page 42
Thermal considerations
page 73
Thermal considerations
page 73
USB handshaking
page 62
USB handshaking
page 62
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