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COM Express® Carrier Board Design Guide
2.15.1 Signal Definitions
Table 15:
System Management Bus Signals
Signal
Pin
Description
I/O
Power Rail
SMB_CK
B13
System Management Bus
bidirectional clock line
I/O OD CMOS
3.3V
Suspend rail
SMB_DAT
B14
System Management
bidirectional data line.
I/O OD CMOS
3.3V
Suspend rail
SMB_ALERT#
B15
System Management Bus
Alert
I CMOS
3.3V
Suspend Rail
2.15.2 Routing Considerations
The SMBus should be connected to all or none of the PCIe/PCI devices and slots. Do not
connect these devices to the SMBus. The maximum load of SMBus lines is limited to 3
external devices.
Do not connect Non-Suspend powered devices to the SMBus unless a bus switch is used
to prevent back feeding of voltage from the Suspend rail to other supplies.
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...
