Sierra Wireless AirPrime WP7504, Hardware Integration Manual, Page: 16 / 24

Hardware Integration Guide
Specifications subject to change 16 4119157
USB Interface
When the USB interface is externally accessible, ESD protection is required on
the USB_VBUS, USB_D+, and USB_D- signals.
Thermal Considerations
When transmitting, the AirPrime WP7504 can generate significant amounts of
heat (due to the internal Power Amplifier) that must be dissipated in the host
device for safety and performance reasons.
The amount of thermal dissipation required depends on the following factors:
• Supply voltage — Maximum power dissipation for these modules can be up to
3 W at voltage supply limits.
• Usage — Typical power dissipation values depend on the location within the
host, amount of data transferred, etc.
To enhance heat dissipation:
• Maximize airflow over / around the module
• Locate the module away from other components that generate heat
• Ensure the module is connected to a solid ground plane
EMC and ESD Recommendations
EMC tests must be performed on the application as soon as possible to detect
any potential problems.
When designing, special attention should be paid to:
• Possible spurious emissions radiated by the application to the RF receiver in
the receiver band
• ESD protection — Typically, ESD protection is mandatory for externally acces-
sible signals, including:
· VBAT_RF / VBAT_BB
· UIM (if accessible from outside)
· Serial link
· USB
· Antennas
• Length of the UIM interface lines (preferably <10 cm)
• Length of the HSIC interface lines (<10 cm, as required by the HSIC specifi-
cation)
• EMC protection on audio input/output (filters against 900 MHz emissions)
• Ground plane: Sierra Wireless recommends a common ground plane for
analog/digital/RF grounds
Note: The AirPrime WP7504 does not include any protection against over-voltage.