Stack-Up Selection, Component Placement on a PCB | Intel IXP46X

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

Figure 19. Component Placement on a PCB


					C
		Medium Frequency			C
		Medium Frequency			O
					N
					N
		High Frequency			N
		Components			E
		Components			C
					C
					T
					O
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, IXP45X manual Stack-Up Selection, Component Placement on a PCB

Contents

Hardware Design Guidelines February HDD Contents 12.1 Figures Control Group Topology Transmission Line Characteristics Tables Revision History Date Revision Description HDD Content Overview Chapter Name Description Related Documentation Title Document # Overview List of Acronyms and AbbreviationsTerm Explanation Smii Intel IXP465 Component Block Diagram Typical Applications Dslam System Architecture Description System Memory Map Intel IXP465 Example System Block Diagram Soft Fusible Features Signal Type DefinitionsSymbol Description Signal Interface Soft Fusible FeaturesDDR-266 Sdram Interface DDR Sdram Interface Pin Description Sheet 1 DDR Sdram Interface Pin Description Sheet 2 DdriwenDdrircveninn Ddrircomp Expansion Bus DDR Sdram Memory InterfaceDDR Sdram Initialization Reset Configuration Straps Expansion Bus Signal RecommendationsInput Pull Name Recommendations Output Down Boot/Reset Strapping Configuration Sheet 1 Name Function Description Boot/Reset Strapping Configuration Sheet 2 3 8-Bit Device Interface4 16-Bit Device Interface 5 32-Bit Device Interface Bit Device 16/32-Bit Device Interface Byte Enable Flash Interface Flash Interface Example Uart Interface Sram InterfaceDesign Notes Uart Signal Recommendations Name Input Pull Recommendations Output Down MII/SMII Interface Uart Interface Example Signal Interface MII MII NPE a Signal RecommendationsMII NPE B Signal Recommendations Sheet 1 MII NPE B Signal Recommendations Sheet 2 MII NPE C Signal Recommendations MAC Management Signal Recommendations NPE A,B,C Device Connection, MIINPE A,B,C Signal Interface, Smii Smii Signal Recommendations NPE A, B, C Gpio Interface Device Connection, Smii Gpio Signal Recommendations I2C Signal Recommendations I2C InterfaceDevice Connection USB Interface I2C Eeprom Interface Example USB Host/Device Signal Recommendations Host Device Utopia Level 2 Interface USB Device Interface Example Utopia Signal Recommendations HSS Interface Utopia Interface Example High-Speed, Serial Interface HSSTXDATA0HSSTXCLK0 HSSRXDATA0 HSSTXDATA1 HSSTXCLK1HSSRXDATA1 HSSRXCLK1 SSP Interface HSS Interface Example Synchronous Serial Peripheral Port Interface PCI Interface PCI Controller Sheet 1Input Pull Name Outpu Recommendations Down PCI Interface Block Diagram PCI Controller Sheet 2 Supporting 5 V PCI Interface PCI Interface PCI Option Interface PCI Host/Option Interface Pin Description Sheet 1 PCI Host/Option Interface Pin Description Sheet 2 Jtag Interface PCI Host/Option Interface Pin Description Sheet 3 Clock Signals Clock SignalsInput System Clock Clock Oscillator Power Power Interface Sheet 1Name Nominal Description Voltage Power Sequence Reset TimingDe-Coupling Capacitance Recommendations VCC De-Coupling HDD HDD Component Placement PCB OverviewGeneral Recommendations Component Selection Component Placement on a PCB Stack-Up Selection Controlled-impedance traces Low-impedance power distribution Layer Stackup General Layout and Routing Guide General Layout Guidelines Signal Changing Reference Planes General Component Spacing Good Design Practice for VIA Hole Placement Clock Signal Considerations Pad-to-Pad Clearance of Passive Components to a PGA or BGA Smii Signal Considerations MII Signal ConsiderationsUSB Considerations Cross-Talk EMI-Design Considerations Power and Ground Plane Trace Impedance HDD Electrical Interface Topology@33 MHz @66 MHz Clock Distribution PCI Address/Data Routing GuidelinesParameter Routing Guidelines Trace Length Limits PCI Clock Routing Guidelines Signal Loading Routing Guidelines DDR Signal Groups Group Signal Name Description No of Single Ended SignalsIntroduction DDRIDQS40 DDR Sdram HDD Supported Memory Configurations Clock Banks Memory Size VTT Selecting VTT Power Supply VTT Terminating Circuitry DDR Command and Control Setup and Hold Values Symbol Parameter Min Max UnitsDdrmclk DDR Data to DQS Read Timing Parameters DDR-Data-to-DQS-Write Timing Parameters DDR Data to DQS Write Timing Parameters Printed Circuit Board Layer Stackup Printed Circuit Board Controlled Impedance Printed Circuit Board Layer Stackup Printed Circuit Board Controlled Impedance Signal Group Absolute Minimum Absolute Maximum Length Timing RelationshipsTiming Relationships Resistive Compensation Register Rcomp Clock Group Clock Signal Group Routing Guidelines Data, Command, and Control Group Routing GuidelinesParameter Definition DDRIBA10, DDRIRASN, DDRICASN, Ddriwen Clock Group Topology Transmission Line Characteristics Simulation ResultsClock Group Transmission Line Length DDR Clock Topology Two-Bank x16 Devices Data Group DDR Clock Simulation Results Two-Bank x16 Devices Data Group Topology Transmission Line Characteristics DDR Data Topology Two-Bank x16 Devices DDR Data Write Simulation Results Two-Bank x16 Devices HDD HDD Control Group Topology Transmission Line Characteristics Control Group DDR RAS Simulation Results Two-Bank x16 Devices Command Group Command Group Topology Transmission Line Characteristics DDR Command MA3 Topology Two-Bank x16 Devices DDR Address Simulation Results Two-Bank x16 Devices DDR Command RAS Topology Two-Bank x16 Devices 104 Rcvenin and Rcvenout DDR RCVENIN/RCVENOUT Topology DDR RCVENIN/RCVENOUT Simulation Results Rseries = 0 Ω DDR RCVENIN/RCVENOUT Simulation Results Rseries = 60 Ω 108