Integration Manual

ANNA-B4 series - System integration manual
UBX-21000517 - R03 Contents Page 28 of 76
C1-Public
• Verify the recommended maximum signal skew for differential pairs and length matching of
buses.
• Minimize the routing length. Ensure that the maximum allowable length for high-speed buses is
not exceeded. Longer traces generally degrade signal performance.
• Track impedance matched traces. Consult with your PCB manufacturer early in the project for
proper stack-up definition.
• Separate the RF and digital sections of the board.
• Ground splitting is not allowed under the module.
• Minimize the bus length to reduce potential EMI issues from digital buses.
• All traces (including low speed or DC traces) must couple with a reference plane (GND or power);
Hi-speed buses should be referenced against the ground plane. If any ground reference needs to
be changed, an adequate number of GND vias must be added in the area that the layer is switched.
This is necessary to provide a low impedance path between the two GND layers for the return
current.
• Hi-Speed buses are not allowed to change reference plane. If changes in the reference plane are
unavoidable, capacitors must be added in the transition area of the reference planes. This is
necessary to ensure that a low impedance return path exists through the different reference
planes.
• Following the “3w rule”, keep traces at a distance no less than three times that of its own width
from the routing edge of the ground plane.
• For EMC purposes and the need to shield against any potential radiation, it is advisable to add GND
stitching vias around the edge of the PCB. Traces on the PCB peripheral are not recommended.
ESD guidelines
Device immunity against Electrostatic Discharge (ESD) is a requirement for Electromagnetic
Compatibility (EMC) conformance and use of the CE marking for products intended for sale in Europe.
To bear the CE mark, all application products integrating u-blox modules must be conformance tested
in accordance with the R&TTE Directive (99/5/EC), EMC Directive (89/336/EEC), and Low Voltage
Directive (73/23/EEC) issued by the Commission of the European Community.
Compliance with the above directives also implies conformity to the following European norms for
device ESD immunity: ESD testing standard CENELEC EN 61000-4-2 and radio equipment standards
ETSI EN 301 489-1, ETSI EN 301 489-7, ETSI EN 301 489-24. The ESD immunity requirements for each
of these standards are summarized in Table 14.
The ESD immunity test is performed at the enclosure port, which is defined by ETSI EN 301 489-1 as
the physical boundary through which the electromagnetic field radiates. If the device implements an
integral antenna, the enclosure port is seen as all-insulating and includes conductive surfaces to
house the device. If the device implements a removable antenna, the antenna port can be separated
from the enclosure port. The antenna port includes the antenna element and its interconnecting cable
surfaces.
Any extension of the ESD immunity test to the whole device is dependent on the device classification,
as defined by ETSI EN 301 489-1. Applicability of the ESD immunity test to the related device ports, or
the interconnecting cables to auxiliary equipment, depends on the device-accessible interfaces and
manufacturer requirements, as defined by ETSI EN 301 489-1.
Contact discharges are performed on conductive surfaces, while air discharges are performed on
insulating surfaces. Indirect contact discharges are performed on the measurement setup horizontal
and vertical coupling planes as defined in CENELEC EN 61000-4-2.
☞ The terms “integral antenna”, “removable antenna”, “antenna port”, “device classification” used
in the context of this guideline are defined in ETSI EN 301 489-1. The terms “contact discharge”
and “air discharge” are defined in CENELEC EN 61000 4-2.