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Intel IXP46X 4.5Stack-UpSelection, Inexpensive, Component Placement on a PCB, Medium Frequency

Models: IXP45X IXP46X

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Figure 19. Component Placement on a PCB

Intel® IXP45X and Intel® IXP46X Product Line of Network Processors—Category

Figure 19. Component Placement on a PCB


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		Medium Frequency			C
		Medium Frequency			O
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		High Frequency			N
		Components			E
		Components			C
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Analog Circuit		Low Frequency			R
Analog Circuit		Low Frequency

PCB

B2264-01

•Place noisy parts (clock, processor, video, etc.) at least 1.5 – 3 inches away from the edge of the printed circuit board.

•Do not place noisy components close to internal/external cables

—Any loose cables picks up noise and act as an antenna to radiate that noise

—Be aware of the peak in-rush surge current into the device pins. This surge current may inject high-frequency switching noise into power planes of the printed circuit board.

•Place high-current components near the power sources.

•Do not share the same physical components (such as buffers and inverters) between high-speed and low-speed signals. Use separate parts.

•Place clock drivers and receivers such that clock trace length is minimized.

•Place clock generation circuits near a ground stitch location. Place a localized ground plane around the clock circuits and connect the localized plane to system ground plane.

•Install clock circuits directly on the printed circuit board, not on sockets.

•Clock crystals should lie flat against the board to provide better coupling of electromagnetic fields to the board.

4.5Stack-Up Selection

Stack-up selection directly affects the trace geometry which, in turn, affects the characteristic impedance requirement for the printed-circuit board. Additionally, the “clean,” noise-free-planes design and placement is significantly important as components run at higher speeds requiring more power.

Considerations include:

•Low-speed, printed-circuit-board construction — for example two-layer boards:

—Advantages:

•Inexpensive

•Manufactured by virtually all printed-circuit-board vendors

—Disadvantages:

Intel® IXP45X and Intel® IXP46X Product Line of Network Processors
HDD	February 2007
60	Document Number: 305261; Revsion: 004

Image 60

Intel IXP46X 4.5Stack-UpSelection, Inexpensive, Component Placement on a PCB, Medium Frequency, High Frequency, Components

Contents

Hardware Design Guidelines FebruaryDocument No 305261 Revision February Contents IntroductionFebruary 5.0 General Layout and Routing Guide6.0 PCI Interface Design Considerations Document Number 305261, RevisionFigures Tables Revision History DateRevision DescriptionFebruary 1.1Content Overview 1.0Introduction1.2Related Documentation 1.3Acronyms and Abbreviations 1.4OverviewList of Acronyms and Abbreviations 32-bitPCI interface Master/Target 33/66 MHz Figure 1. Intel IXP465 Component Block Diagram MII/SMIICryptography Unit1.5Typical Applications 2.0System Architecture 2.1System Architecture Description2.2System Memory Map JTAG IntelIXP46X ProductLine of Network Processors3.1Soft Fusible Features Signal Type Definitions3.0General Hardware Design Considerations Table3.2.1Signal Interface Soft Fusible Features3.2DDR-266SDRAM Interface DDR SDRAM Interface Pin Description Sheet 1 ofDDR SDRAM Interface Pin Description Sheet 2 of 3.3Expansion Bus 3.2.2DDR SDRAM Memory Interface3.2.3DDR SDRAM Initialization 3.3.1Signal Interface 3.3.2Reset Configuration StrapsExpansion Bus Signal Recommendations Boot/Reset Strapping Configuration Sheet 1 of TableName FunctionBoot/Reset Strapping Configuration Sheet 2 of 3.3.38-BitDevice Interface3.3.416-BitDevice Interface 3.3.532-BitDevice Interface Byte Access 16-Bit-WordAccess32-Bit-WordAccess 8-BitDeviceByte Access 16-Bit-WordAccess32-Bit-WordAccess 8-BitDeviceIntel Flash 3.3.6Flash InterfaceFigure 5. Flash Interface Example 16-Bit-WordAccess3.4UART Interface 3.3.7SRAM Interface3.3.8Design Notes Figure 6. Expansion Bus SRAM Interface3.4.1Signal Interface UART Signal RecommendationsConnector MII/SMII InterfaceFigure 7. UART Interface Example UART Interface3.5.1Signal Interface MII MII NPE A Signal RecommendationsMII NPE B Signal Recommendations Sheet 1 of MII NPE B Signal Recommendations Sheet 2 of MII NPE C Signal Recommendations3.5.2Device Connection, MII Figure 8. MII Interface Example10/100 3.5.3Signal Interface, SMII 3.6GPIO Interface 3.5.4Device Connection, SMIIFigure 9. SMII Interface Example 3.6.1Signal Interface GPIO Signal Recommendations3.6.2Design Notes 3.7.1Signal Interface I2C Signal Recommendations3.7I2C Interface 3.7.2Device Connection3.8USB Interface Figure 10. I2C EEPROM Interface ExampleProduct Line Network Processor3.8.1Signal Interface USB Host/Device Signal Recommendations3.8.2Device Connection Figure 11. USB Host Down Stream Interface ExampleHost Device3.9UTOPIA Level 2 Interface Figure 12. USB Device Interface ExampleDevice Host3.9.1Signal Interface UTOPIA Signal Recommendations3.9.2Device Connection 3.10HSS Interface Figure 13. UTOPIA Interface ExampleAnalog Front ATM Layer Device3.10.1Signal Interface High-Speed,Serial InterfaceHigh-Speed,Serial Interface Transmit frame3.11SSP Interface 3.10.2Device ConnectionFigure 14. HSS Interface Example 3.11.1Signal Interface 3.11.2Device ConnectionSynchronous Serial Peripheral Port Interface SPI Flash3.12.1Signal Interface 3.12PCI InterfacePCI Controller Sheet 1 of 3.12.2PCI Interface Block Diagram PCI Controller Sheet 2 of3.12.3Supporting 5 V PCI Interface Figure 16. PCI InterfaceCompact PCI Bus cPCI J13.12.4PCI Option Interface 3.3V LogicPCI Device PCI DevicePage 3.13JTAG Interface 3.12.5Design Notes3.13.1Signal Interface 3.14.1Clock SignalsClock Signals 3.14Input System Clock3.15Power 3.14.3Device ConnectionIntel IXP46X 3.15.5Power Sequence 3.15.6Reset TimingPower Interface Sheet 2 of 3.15.1De-CouplingCapacitance RecommendationsFebruary Document Number 305261 RevisionFebruary Document Number 305261 Revision4.4Component Placement 4.0General PCB Guide4.1PCB Overview 4.2General RecommendationsFigure 19. Component Placement on a PCB 4.5Stack-UpSelectionInexpensive Medium FrequencyUncontrolled signal trace impedance Low-impedancepower distributionHigher cost More weight Poor routing densityFigure 20. 8-LayerStackup Figure 21. 6-LayerStackup5.0General Layout and Routing Guide 5.1Overview5.2General Layout Guidelines Figure 22. Signal Changing Reference Planes 5.2.1General Component SpacingVIAs Figure 24. Poor Design Practice for VIA Placement 25 mils min 25 mils min 25 mils minFlush Via min Potential Bridge min 5.2.2Clock Signal Considerations PGA or BGA Package5.2.3SMII Signal Considerations 5.2.4MII Signal Considerations5.2.5USB Considerations 5.2.6Cross-Talk 5.2.7EMI-DesignConsiderations5.2.9Power and Ground Plane 5.2.8Trace ImpedanceFebruary Document Number 305261 RevisionFebruary Document Number 305261 Revision6.0PCI Interface Design Considerations 6.1Electrical Interface6.2Topology 6.3Clock Distribution Figure 26. PCI Address/Data TopologyPCI Slot Table 25. PCI Address/Data Routing Guidelines6.3.1Trace Length Limits PCI DevicesClock Driver6.3.3Signal Loading 6.3.2Routing GuidelinesFebruary DDR Signal Groups 7.0DDR-SDRAM7.1Introduction TableFigure 28. Processor-DDRInterface ProcessorsLine of Network DDR SDRAMFebruary Document Number: 305261, Revision:Supported Memory Configurations VTT Signal Termination SignalTermination Intel IXP46X7.1.1Selecting VTT Power Supply Figure 30. VTT Terminating CircuitryIXP46X DDR SDRAMFigure 31. DDR Command and Control Setup and Hold Control/Command ValidDDR M CLK 7.1.2Signal-TimingAnalysisFigure 32. DDR Data to DQS Read Timing Parameters DataDDR Data to DQS Read Timing Parameters Figure 33. DDR-Data-to-DQS-WriteTiming Parameters Data ValidDDR Data to DQS Write Timing Parameters Data7.1.3Printed Circuit Board Layer Stackup DDR-Clock-to-DQS-WriteTiming Parameters7.1.4Printed Circuit Board Controlled Impedance Figure 35. Printed Circuit Board Layer StackupFebruary 7.1.5Timing Relationships Figure 31 on page -Table 29 on page—Table 30 on page —Table 31 on page Figure 32 on page -Table 30 on page7.1.6Resistive Compensation Register Rcomp 7.1.7Routing Guidelines7.1.7.1Clock Group 7.1.7.2Data, Command, and Control Groups Clock Signal Group Routing Guidelines7.2Simulation Results 7.2.1Clock GroupFebruary Document Number: 305261, Revision:7.2.2Data Group FebruaryTL1 Tpd = 175 ps/in Figure 39. DDR Data Topology Two-Bankx16 Devices FebruaryFebruary Document Number: 305261, Revision:February February Document Number 305261, Revision7.2.3Control Group February Document Number 305261, Revision7.2.4Command Group TL1 Tpd = 175 ps/inTL2 Tpd = 175 ps/in TL3 Tpd = 175 ps/inFebruary Document Number 305261, RevisionFebruary February Document Number 305261, RevisionFebruary 7.2.5RCVENIN and RCVENOUT Figure 49. DDR RCVENIN/RCVENOUT TopologyFebruary February Document Number 305261, RevisionFebruary Document Number 305261, Revision