Advantech SOM-Express Design Guide
4 Table of Contents
2.6.2 Universal Serial Bus (USB) AC Spec. ..........................................29
2.6.3 Audio AC Spec. ............................................................................29
2.6.4 VGA AC Spec...............................................................................29
2.6.5 IDE AC Spec.................................................................................30
2.6.6 I2C AC Spec.................................................................................30
2.6.7 SMBus AC Spec...........................................................................30
Chapter 3 Pin Assignments .................................................................................31
Table 3.1 Conventions and Terminology......................................31
3.1 Row A ....................................................................................................32
Table 3.2 Connector A Pin Assignments......................................32
3.2 Row B ....................................................................................................33
Table 3.3 Connector B Pin Assignments.....................................33
3.3 Row C....................................................................................................34
Table 3.4 Connector C Pin Assignments......................................34
3.4 Row D....................................................................................................35
Table 3.5 Connector D Pin Assignments......................................35
Chapter 4 General Design Recommendations ...................................................36
4.1 Nominal Board Stack-Up .......................................................................36
4.1.1 Four layer board stack-up.............................................................37
Figure 4-1 Four-Layer Stack-up...................................................37
Table 4.1: Recommended Four-Layer Stack-Up Dimensions ......37
4.1.2 Six layer board stack-up ...............................................................38
Figure 4-2 Six-Layer Stack-up ......................................................38
Table 4.2 Recommended Six-Layer Stack-Up Dimensions.........38
4.2 Differential Impedance Targets for Microstrip Routing ..........................39
Table 4.3 Differential Signals Impedance Requirement ...............39
4.3 Alternate Stack Ups...............................................................................39
Chapter 5 Carrier Board Design Guidelines .......................................................40
5.1 PCI-Bus .................................................................................................40
5.1.1 Signal Description.........................................................................40
Table 5.1 PCI Signal Description..................................................40
5.1.2 Design Guidelines.........................................................................41
Table 5.2 Carrier PCI Slots..........................................................41
Table 5.3 Carrier PCI Slots/Devices Interrupt Routing Table ......41
Figure 5-1 Routing PCI Slot/Device CSB Interrupt .......................42
Table 5.4 Clock Skew Parameters ...............................................42
Figure 5-2 Clock Skew Diagram...................................................43
Table 5.5 Maximum Add-in Card Loading via Each Power Rail ...43
Table 5.6 Add-in Card Supplied Power Selection.........................44
5.1.3 Layout Guidelines.........................................................................44
Figure 5-3 PCI Bus Layout Example with IDSEL..........................44
Table 5.7 PCI Data Signals Routing Summary.............................45
Figure 5-4 PCI Clock Layout Example..........................................45
Table 5.8 PCI Clock Signals Routing Summary ...........................45
5.1.4 Application Notes..........................................................................46
Figure 5-5 Design Example: PCI Arbiter.......................................46
5.2 Universal Serial Bus (USB) ...................................................................47
5.2.1 Signal Description.........................................................................47
Table 5.9 USB Signals Description...............................................47
5.2.2 Design Guidelines.........................................................................47
Figure 5-6 USB Connections........................................................47
Figure 5-7 Common Mode Choke ................................................48
5.2.3 Layout Guideline...........................................................................48
Figure 5-8 USB Layout Guidelines ...............................................49
Figure 5-9 Overcurrent Circuit ......................................................49
