Xplore Technologies Corp. MC7750 Manual Do Utilizador
B
Rev 4 Sep.11
Proprietary and Confidential - Contents subject to change
69
B: Design Checklist
This chapter provides a summary of the design considerations
mentioned throughout this guide. This includes items relating to the
power interface, RF integration, thermal considerations, cabling
issues, and so on.
mentioned throughout this guide. This includes items relating to the
power interface, RF integration, thermal considerations, cabling
issues, and so on.
Note: This is NOT an exhaustive list of design considerations. It is expected
that you will employ good design practices and engineering principles in your
integration.
that you will employ good design practices and engineering principles in your
integration.
Table B-1: Hardware integration design considerations
Suggestion
Section where discussed
Component placement
Protect the SIM socket so the SIM cannot be removed while the
host is powered up.
If an ESD suppressor is not used, allow space on the SIM
connector for series resistors in layout. (Up to 100
may be
used depending on ESD testing requirements).
Minimize RF cable losses as these affect performance values
listed in product specification documents.
Antennas
Match the module / antenna coax connections to 50
—
mismatched antenna impedance and cable loss negatively
affect RF performance.
affect RF performance.
If installing CDMA and UMTS modules in the same device,
consider using separate antennas for maximum performance.
Power
Make sure the power supply can handle the maximum current
specified for the module type.
Limit the total impedance of VCC and GND connections to the
SIM at the connector to less than 1
(including any trace
impedance and lumped element components — inductors, filters,
etc.). All other lines must have a trace impedance less than 2
etc.). All other lines must have a trace impedance less than 2
.
Decouple the VCC line close to the SIM socket. The longer the
trace length (impedance) from socket to module, the greater the
capacitance requirement to meet compliance tests.
capacitance requirement to meet compliance tests.
EMI / ESD
Investigate sources of localized interference early in the design
cycle.