Lantronix XPort Integration Manual - Recommended Pcb Layout
2 Description and Specifications
XPort™ Integration Guide
11
Recommended PCB Layout
The hole pattern and mounting dimensions for the XPort device server are shown in
the following drawing. For proper heat dissipation, it is recommended that the PCB
have approximately 1 square inch of copper attached to the shield tabs. The shield
tabs are an important source of heat sinking for the device.
The XPort shield is considered “chassis ground” and should be separate from “signal
ground”. ESD near the XPort at the panel opening will likely jump to the shield.
We recommend using high voltage (~200V), low ESR, 0.01uF capacitors to connect
chassis ground to both signal ground and 3.3V. This will cause any voltage spike
from ESD to be imparted equally to both signal ground and 3.3V with no net voltage
increase between 3.3V and signal ground. For the highest level of ESD protection of
the XPort, it is recommended that the shield not be directly connected to signal GND.
The metal shield fingers around the XPort’s RJ45 should physically contact the
product housing when the housing is metal, or metallic coated.
The shield is also a heat sink for the internal EX Processor. As in all heat sinking
applications, the more copper connected to the heat sink the better. Adding 1 inch
square inch of copper flood on the PCB is adequate to allow the XPort to work up to
+85°C. If the application does not expect to see t emperatures up to +85°C the heat
sink may be smaller than 1 square inch.
Figure 2-7 PCB Layout