Class01 Introduction

8/2/2019 Class01 Introduction

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Signal Integrity Introduction


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What is Signal Integrity (SI)?

An Engineering PracticeThat ensures all signals transmitted arereceived correctly

That ensures signals dont interfere with

one another in a way to degrade reception. That ensures signal dont damage any

device

That ensures signal dont pollute theelectromagnetic spectrum


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Whats this all about?

$


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The Business

Determine design parameters forsuccessful signaling

Design parameters are ranges fordesign variables within which aproduct can be reliably built One in row is not good enough

New TermsGeneral SolutionPoint Solution

Specific Solution


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SI Paradigms

Specific Solution Applies to a given instance of a product or specimen

Point Solution

Applies to any single given product Encompasses a locus of specific solutions.

Example: Any board that comes off a production line

General Solution

Applies to many products of a given type Encompasses a locus of point solutions

The locus of all solutions for a specific standard (likeSCSI) is an example.


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Effective SI is Pre-Product Release.

It costs less here.

Why? Time = $

0

10

20

3040

50

Cost of

failure

(M$)

Pre-prototype

Validation Post Release


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What About Design Functionality?

Normally not the domain of SI Often qualifies legal operation

For most computers I/O signals are v(t)

Core: IC logic

Transmitter

InterconnectReceiver


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Components of High Speed Design

Competitive performance goals challenge each generation oftechnology (higher frequencies)

SI encompasses a conglomerate of electrical engineeringdisciplines

Transmitter

Interconnect

Receiver

Circuit elements Transmission lines

S parameter blocks(advanced topic)

Transistors Sources Algorithms Passives Memory

Transistors Passives Algorithms Memory


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SI Work

Modeling

Simulation

Measurement

Validation

What is good enough?

Sufficient to operate at desired frequency with

required fidelity

Risk Assessment

SI i C Th 60 d


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SI in Computers The 60s and

70s

7400 Class TTL

Several MHz operation and 5ns edges

Transistor -Transistor Logic

Logic design with jelly bean ICs

Using loading rules from spec books

Lots of combinational and asynchronous one-shot designs.

Bipolar and CMOS


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The 60s and 70s - Continued

ECL Emitter Coupled Logic

Tens of MHz and 2-3ns edge rates

MECL hand bookOne of the first books on SI

Introduced concept of termination and transmission lines

Still used spec books for rules

A few engineers evaluated termination schemes but no

SI engineering per se

Common SI problems were deglitching switches

and specifying clamping diodes on relay drivers.


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The 80s

Hi Speed CMOS and open drain buses

100+ MHz operation and 1ns edges

Clocking issues start to creep in here

Ringing becomes a problem

Timing simulators emerge for SI


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The 90s Early in the decade extracted board simulators are popular.

Chip I/V and edge V(t) info simulated with transmission lines whosecharacteristics are extracted directly from PWB layout information

IBIS becomes popular

Edge rates move toward 300ps at launch.

Memory and I/O buses require early SI analysis

SSTLseries stub terminated AGTLAdvanced Gunning Transistor Logic

Open collector busing

Differential signaling emerges

Late in the decade we start to hear terms like return path, I/Opower delivery, ISI, and source-synch Extracted board simulators dont account for these


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The 00s

GHz operation and 50ps launch edges SI Engineers using spice and modeling with

Maxwell 2D/3-D field solvers.

Emerging technologiesHigh Speed Serial Differential

De/Pre emphasis

Embedded clockingData encoding

Pulse Amplitude Modulation (PAM)

Simultaneous Bi-Directional (SBD)


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Assignment

Assignment: How much electrical transmission length does

a 5ns, 2.5ns, 1ns, 300ps, 50ps edge occupy? Assume

propagation velocity is half that free of space.

Determine a rationale for specifying physical wiring length

in computer printed wiring boards. This is an exercise in

engineering judgment.

Plot the ratio of electrical edge length to board trace length

(by decade) in previous slide. Use range plots.


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SI Directions Today

SI is starting to borrow from the

communications industry

We are starting to hear terms likeVector Network Analyzer (VNA)

S-parameters

Return and insertion loss

Eye diagram


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SI Roles

Convert product parts and design features into

models and parameters

Use models to simulate performance Perform measurements to validate product

Determine how parameters limit performance

Use cost and simulated or measured performanceto determine rules for design

Use margin budgets to manage designs


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SI Deliverables

SI Customer

Product

Architect

Product

Designer

Product

Manager

Deliverables

"What if ? " Rules

Use measurement

to ensure

confidence in

simulations

decisions

FeasibilityCost/Performance

TradeoffNo Field Failures

Assignment: Fill in the above 6 boxes with

hypothetical examples based on yourpresent knowledge of the computerengineering field.


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Future of SI

Rules of thumb get old quick

Old assumptions not good enoughfascinatingtopics Can we still use transmission line models?

What is the role of ground? Higher and higher frequency

Underscores the need to understand 2nd and 3rd ordereffects.

List examples Many EE disciplines play together

Plethora of new signal analysis and measurement methods

Need to simplify designs to efficiently turn a profit.

Documents

Class01 Introduction