7
Rev 1.9.1 Feb.09
Proprietary and Confidential
75
In the event of a discrepancy in values between this guide and the Product Specification Document (PSD), the PSD takes precedence.
7: 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.
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.
Table 7-1: Hardware integration design considerations
Suggestion
Section where discussed
Component placement
Protect the USIM socket so that the USIM cannot be removed
while the host is powered up.
If an ESD suppressor is not used, allow space on the USIM
connector for series resistors in layout (up to 100
Ω
may be used
depending on ESD testing requirements).
Minimize RF cable losses as these affect the performance values
listed in the product specification document.
Antennas
Match the module / antenna coax connections to 50
Ω
—
mismatched antenna impedance and cable loss negatively
affects RF performance.
If installing both the MC57xx and MC87xx in the same device,
consider using separate antennas for maximum performance.
Power
Limit host power rail dips caused by module inrush current by
adding sufficient capacitance to the host power rail.
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
USIM at the connector to less than 1
Ω
(including any trace
impedance and lumped element components — inductors,
filters, etc.). All other lines must have a trace impedance less
than 2
Ω
.