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ADI 高速、混合、微弱信号布线指南.pdf

The Art of PCB Design

Good PCB design is a discipline that takes

We'll cover many important concepts at a

DB34／T 1469-2019 居住区供配电系统技术标准PCB methodologies originated in the United States

PCBBasicsTypical PcB Design ProcessFabricationTolerance(i.e. min trace width,min hole size, etc.)SchematicDRCReportSchematicPCBCaptureDRC ReportPCBNetlistGerberFilesFabricationLayoutPCBSchematicDrill FileLibraryFootprintLibraryPCBLibrarian and/orParametersdeviceprovider(i.e. core material,copperweight, etc)DRC=DesignRuleCheckADIConfidential

At low frequency, current will follow the pathof least resistance. At high frequency, current will follow the pathofleastinductance

GoodPCB Design!PracticesUnderstanding CapacitorsDifferent types of capacitors..TBADEVICADIConfidential

CaverensHighSpeedPCB Design and LayoutUnderstanding Resistors8008James Bryant's paperTBADEVICADIConfidential

LarerienHighSpeedPCB Design and LayoutChanges in Impedance Across Signal PathtracetracetracecabletraceDevice ADevice BviaviaconnectorconnectorOutputDriverTransmission LineLoadZtypical~500Ztypical 1MQDevice A to Device B, a propagating signal will likelytraverse multiple impedance changes. The largest mismatches will almost always occur at thesource and load.Will generatelargereflections!.Howcanwedeal withthis?Let's look at a story...DEVICEADIConfidential29

MESOSEdgar Meets The"Unterminated"Transmission lineAttributes:Pointtopointconnection25OhmimpedanceOutputDriver. 50 ohm impedance Transmission Line (Zo).1MegOhmimpedancereceiverDriverReceiverTransmissionLineADIConfidential

At The StartThe Driver lowers the voltage by from VDD to GND.DRVERADIConfidential32

Edgar Starts for the ReceiverEdgar travels at 6 inches per nanosecondDriverReceiverTransmissionLineDEVICEADIConfidential33

Edgar Returns to the DriverEdgar travels at 6 inches per nanosecond with most of hisoriginal energy!DriverReceiverTransmissionLineADIConfidentialDEVIC35

MESSLarerenaEdgar ls Sent to the Receiver AgainEdgar travels at 6 inches per nanosecondDriverReceiverTransmissionLineADIConfidentialDEVICE

CaveriersEdgar ls Sent to the Driver AgainEdgar travels at 6 inches per nanosecondDriverReceiverTransmissionLineADIConfidentialDEVICE38

DB34／T 1991-2013 安徽省建筑工程项目信息编码标准LarerierEdgar ls Sent to the Receiver a 'Third TimeEdgar travels at 6 inches per nanosecondDriverReceiverTransmission LineADIConfidentialDEVICE39

everage Ohms' law to minimize the impedance mismatch a

ManagingtheLoadE

Eachmethodhasitsprosandcons.

MENSSDarererHighSpeed PCB Designand'LayoutParallel TerminationParallel resistoratthe receivercanworkwell buthas:.Increases drive current and thus increases power dissipation.IncreasedCrosstalk,IncreasedEMl.Increased ground bounce or supply noise (depending on if theparallel resistor is pulled high or low).DriverDrive currentReceiverabout 50 mATransmission LineDEVICEADIConfidential42

DB37／T 3364-2018 装配式钢结构住宅-钢支撑通用技术要求MENSSDarerentHigh Speed PCB Design and 'LayoutSeries TerminationSeries resistoratthe driverisless disruptive:...but the driver impedance is nonlinear and you lose someenergy getting into the transmission lineDriverReceiverTransmission LineADIConfidentialDEVICE43

CaverfersDDR SDRAM TerminationDDRusesDualterminationAtVCC/2=1.25V,loofthedriverisabout14mADriverReceiverVCC/2Transmission LineADIConfidentialDEVICE

MESSCarererEdaarMeets DDR in the'Real WorldThe Series Resistor Plus the Drive impedance is 50 OhmsTheParallelResistoris50OhmsThe Transmission Line Impedance is 60 Ohms (Bad PCB)DriverReceiverVCC/22550WTransmission LineADIConfidentialDEVIC45