COM Express® Carrier Board Design Guide
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3.3
Routing Considerations
3.3.1 VCC_12V and GND
For the +12V power input (VCC_12V) to the Module, the trace should be wide enough to handle
the maximum expected load. A power plane may be used for VCC_12V but is not
recommended; VCC_12V should not be used as a reference for high-speed signals, such as
PCIe, USB, or even PCI, because there may be switching noise present on VCC_12V.
A 40W CPU Module can draw over 3.5A on the VCC_12V pins. Sizing the VCC_12V delivery
trace to handle at least twice the expected load is recommended. K eep the Carrier Board
VCC_12 trace short, wide, and away from other parts of the Carrier Board.
If there are layer transitions in the power delivery path, use redundant “power” vias – vias that
are sized with larger holes and pads than default vias. For the GND return, use a solid,
continuous plane, or multiple planes, using the heaviest possible copper. Connect all available
power and ground pins available on the COM Express Module to the Carrier Board.
3.3.2 VCC_5SBY Routing
The +5V Suspend power rail should be sized to handle 2A. Most Modules will use less than 2A
for the \power rail. Modules with multiple Ethernet channels and wake-on-LAN capability will
use more current. The COM Express Specification allows up to 2A on this rail.
Summary of Contents for ET976
Page 1: ...COM EXPRESS CARRIER BOARD DESIGN GUIDE Version 1 0 January 2022...
Page 11: ...COM Express Carrier Board Design Guide 5 Figure 3 PCI Express x4 Slot Example...
Page 12: ...6 COM Express Carrier Board Design Guide Figure 4 PCIe Mini Card Reference Circuitry...
Page 19: ...COM Express Carrier Board Design Guide 13 Figure 7 HDMI Example 1...
Page 20: ...14 COM Express Carrier Board Design Guide Figure 7 HDMI Example 2...
Page 21: ...COM Express Carrier Board Design Guide 15 Figure 8 DVI Example 1...
Page 22: ...16 COM Express Carrier Board Design Guide Figure 8 DVI Example 2...
Page 31: ...COM Express Carrier Board Design Guide 25 Figure 12 USB 3 0 Example 2...
Page 37: ...COM Express Carrier Board Design Guide 31 Figure 14 LVDS Reference Schematic 2...
Page 44: ...38 COM Express Carrier Board Design Guide Figure 16 VGA Reference Schematics 2...
Page 48: ...42 COM Express Carrier Board Design Guide Figure 18 HDA Example Schematic 2...
Page 52: ...46 COM Express Carrier Board Design Guide Figure 19 LPC Super I O Example 2...
Page 61: ...COM Express Carrier Board Design Guide 55 Figure 24 General Purpose Serial Port Example 2...
Page 70: ...64 COM Express Carrier Board Design Guide Figure 28 PWRBTN and SYS_RESET Circuitry...
Page 84: ...78 COM Express Carrier Board Design Guide Chapter 4 Carrier Board PCB Layout Guidelines...
