Stack-Up Selection, Component Placement on a PCB | Intel IXP43X

Hardware Design Guidelines—Intel®IXP43X Product Line of Network Processors

Figure 16. 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, and so on.) 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 acts as an antenna to radiate that noise

—Be aware of the peak in-rush surge current into the device pins. This surge current can 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® IXP43X Product Line of Network Processors
April 2007	HDG
Document Number: 316844; Revision: 001US	57

Image 57

Intel IXP43X manual Stack-Up Selection, Component Placement on a PCB

Contents

Hardware Design Guidelines Intel IXP43X Product Line of Network Processors Intel IXP43X Product Line of Network Processors HDGApril Contents Figures Tables Document Number 316844 Revision 001US § § Date Revision Description001 Initial release HDG Chapter Name Description Content Overview Acronyms Related DocumentationList of Acronyms and Abbreviations Sheet 1 Term Explanation List of Acronyms and Abbreviations Sheet 2 Overview HDG Intel IXP435 Network Processor Block Diagram Typical Applications System Memory Map System Architecture Description Intel IXP43X Product Signal Type Definitions Soft Fusible FeaturesSoft Fusible Features Sheet 1 Symbol Description USB Host Each USB can be Enable separately Soft Fusible Features Sheet 2DDRII/I Sdram Interface Ethernet DDRII/I Sdram Interface Pin Description Sheet 1 Signal InterfaceType Name Device-Pin Connection Terminatio Description Field DDRII/I Sdram Interface Pin Description Sheet 2 DDRII/I Sdram Initialization Expansion Bus Signal Recommendations Sheet 1 Expansion BusType Pull Name Recommendations Field Down Expansion Bus Signal Recommendations Sheet 2 Reset Configuration StrapsBoot/Reset Strapping Configuration Sheet 1 Name Type Pull Recommendations Field Down Boot/Reset Strapping Configuration Sheet 2 3 8-Bit Device Interface Setting Intel XScale Processor Operation SpeedIntel XScale Processor Cfg0 Cfg1 Cfgenn Actual Core Speed MHz 4 16-Bit Device Interface 16-Bit Device Interface Flash Interface Flash Interface Example Uart Interface Uart Signal Recommendations Uart Interface Example MII Interface Signal Interface MII MII NPE a Signal RecommendationsMII NPE C Signal Recommendations Sheet 1 MII NPE C Signal Recommendations Sheet 2 MAC Management Signal Recommendations NPE a and NPE CDevice Connection, MII MII Interface Example Gpio Interface Gpio Signal Recommendations USB InterfaceDesign Notes Name Type Pull Description Field Down USB Host Signal Recommendations Common Mode Choke Host Device Utopia Level 2 Interface Utopia Level 2/MIIAType Pull Name Description Field Down UTPOPDATA75 UTPOPDATA4UTPOPADDR40 Utpopfci Utpipfci ClavUtpipsoc ETHARXDATA30 Etharxclk UTPIPDATA6 UTPIPDATA5UTPIPDATA7 UTPIPADDR40 Device Connection HSS Interface HSSTXDATA0 High-Speed, Serial InterfaceHSSTXCLK0 HSSRXDATA0 HSS Interface Example SSP Interface Synchronous Serial Peripheral Port Interface Serial Flash and SSP Port SPI Interface Example PCI Interface PCI Controller Sheet 1 PCI Controller Sheet 2 PCI Interface Block DiagramPciintan Pciclkin PCI Option Interface Connect signal to same pin between PCI Parity Two devicesPCI Host/Option Interface Pin Description Sheet 1 Type Option Description Name Device-Pin Connection Field Signal PCIREQN0 to one PCIREQN30 inputs to the Host On the Option device, these signals are notPCI Host/Option Interface Pin Description Sheet 2 Type Option Name Device-Pin Connection Description Field PCI Host/Option Interface Pin Description Sheet 3 Jtag Interface Clock Signals Clock SignalsInput System Clock Clock Oscillator Recommendations for Crystal Selection Power Power SupplyNominal Name Voltage Description Reset Timing Power SequenceDecoupling Capacitance Recommendations VCC Decoupling § § PCB Overview Component PlacementGeneral Recommendations Component Selection Stack-Up Selection Component Placement on a PCB Controlled-impedance traces Low-impedance power distribution Layer Stackup General Layout Guidelines General Layout and Routing Guide General Component Spacing Signal Changing Reference Planes Good Design Practice for VIA Hole Placement Pad-to-Pad Clearance of Passive Components to a PGA or BGA Clock Signal Considerations MII Signal Considerations USB V2.0 ConsiderationsCrosstalk Power and Ground Plane EMI Design ConsiderationsTrace Impedance § § Topology Electrical Interface@33 MHz Tcyc = 30 nSec Tval = 11 nSec Tprop = 10 nSec Clock Distribution PCI Address/Data Routing GuidelinesParameter Routing Guidelines PCI Clock Routing Guidelines Trace Length Limits Routing Guidelines Signal Loading Introduction Ddrii / Ddri Sdram Group Signal Name Description DDRII/I Signal GroupsDrasn / Ddrrasn Dcasn / Ddrcasn DDR Sdram Supported Ddrii 32-bit Sdram Configurations Supported Ddri 32-bit Sdram ConfigurationsSupported Ddri 16-bit Sdram Configurations Sizea DDRII/DDRI Rcomp and Slew Resistances Pin Requirements Supported Ddrii 16-bit Sdram ConfigurationsAddress Size Leaf Select Total Technology Arrangement Banks DDR-II Symbol Parameter Units Min Max Ddrii OCD Pin RequirementsDDR Clock Timings DDR Sdram Write Timings Symbol Parameter Minimum Nominal Maximum Units DDRII-400 MHz Interface -- Signal Timings Symbol Parameter Minimum Nom Maximum Units DDR II/I Sdram Interface -- Signal TimingsTiming Relationships Printed Circuit Board Layer Stackup Signal Package Lengths Sheet 1 Group Signal Name Length milTiming Relationships Signal Package Lengths Sheet 2 Clock Group Signal Package Lengths Sheet 3 Parameter Definition Data and Control Groups DCB70/DDRCB70, DDQ310 / DDRDQ310 Ddrii Data and Control Signal Group Routing Guidelines Signal Group Members Ddrii Command Signal Group Routing Guidelines § §