micrel hbw i o structures jitter

8/12/2019 Micrel HBW I O Structures Jitter

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I/O Structuresand

Jitter Presentation


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I/O Levels

Parameter LVDS PECL LVPECL CML

VOH 1.425VVCC 0.9V V CC 0.9V V CC -0.2V

VOL 1.1VVCC 1.7V V CC 1.7V V CC 0.6V

VOUT 325mV 800mV 800mV 400mV

Reference GND V CC VCC VCC


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PECL


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PECL Input Structure

V CC V CC

Positive Supply

PECL: Positive Emitter-Coupled-Logic

LVPECL: Low Voltage Positive Emitter-

Coupled-Logic Same Characteristics as ECL

800mV swing Termination to Vcc-2.0V

OUT

IN

OUT

INOutput Structure

Input Structure


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PECL Termination

PECL

V CC -2V

50 50

V CC

VOH=VCC -0.9VVOL=VCC -1.7V

IOH

=22mA

IOL=6mA


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CML


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CML Input Structure

V CCCC

5

IN

IN


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CML Output Structure

V CC

5 5

OUT

OUT

16mA


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CML Terminations

CML

VCC

VCC

50

50

16mA

100

VCC

VCC

50

50

16mA

50

VCC

50

VOH=VCCVOL=VCC -0.4V

VOH=VCC -0.2VVOL=VCC -0.6V


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LVDS


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LVDS Input Structure

V CC

IN

IN


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LVDS Output Structure

V CC

OUT

OUT

VCCS VCCS


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LVDS Termination

VOH=1.425V

VOL=1.100V

VCC

100

VCCS

VCCS


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Micrel Any-In


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Precision Edge Patented Designs

Any-In is simple Internal TerminationImproves Jitter PerformanceSimplifies Designs

Eliminates external componentsEliminates Stubs in Layout


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Any-In Input Structure

V CC

IN

IN

5

5

VT

Termination

Inside Chip


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The Any-In Advantage

V CC

IN

IN

Conventional

V CC V CC

IN

IN

5

5

VT

Any-In


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Jitter Discussion

h


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What is Jitter

Jitter is the deviation from the ideal timing of an event. Jitter is composed of both deterministic and Gaussian (random) content. Total Jitter (TJ) is the convolution of all independent Jitter Components.

Example: 1ns of Jitter in a 100Mbps signal represents a 10% data uncertainty.

Ji V Sk


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Jitter Versus Skew

Q1

Q2

Q3

Jitter: The deviation of a timing eventfrom its ideal position. Skew: The difference betweenmultiple signal outputs

T f Ji


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Types of Jitter

TJ

RJDJ

PJ DDJ

ISIDCD

Bounded (Pk-Pk)

Unbounded (RMS)

TJ = Total Jitter DJ = Deterministic Jitter RJ = Random Jitter (Gaussian)PJ = Periodic Jitter DDJ = Data Dependent Jitter DCD = Duty Cycle Distortion

ISI = Intersymbol Interference

R d Jitt


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Random Jitter

Random Jitter has a Gaussian distributionand is unbounded (RMS).

Unbounded so Peak-to-Peak numbers need tobe qualified.

3 types, Adjacent-Edge, Cycle-to-Cycle and Period

Common sources of RJ:

Shot Noise, Flicker Noise (1/f) and Thermal Noise

TJ

RJDJ

PJ DDJ

ISIDCD

Bounded (Pk-Pk)

Unbounded (RMS)

Semiconductor Originated

D t i i ti Jitt


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Deterministic Jitter

Deterministic Jitter is non-Gaussian andbounded (Pk-Pk).

Additive, i.e. a simple summation.

Common sources of DJ:EMI, Crosstalk, and Reflections

TJ

RJDJ

PJ DDJ

ISIDCD

Bounded (Pk-Pk)

Unbounded (RMS)

System Related

DJ PWD/DCD E ample


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DJ, PWD/DCD Example

PWD/DCD is characterized as having an asymmetric rise/fall time Also see this with re-bias mismatch


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DJ Limited Channel Bandwidth


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DJ Limited Channel Bandwidth

HF PJ

Long Consecutive Bit Stream

Midpoint

0-1-0Bit Stream

Classify the following into types of jitter Limited channel bandwidth

PJ/DDJ/ISI

Total Jitter


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Total Jitter

TJ

RJDJ

PJ DDJ

ISIDCD

Bounded (Pk-Pk)

Unbounded (RMS)

Total Jitter is the convolution of allindependent jitter components.

TJ = DJ (p-p) + a * RJ (rms)a = 12 for 10 -9 BERa = 14 for 10 -12 BER (commonly assumed)a = 16 for 10 -15 BER

Adding Jitter Components:DJ TOT = DJ 1 + DJ 2RJ TOT 2 = RJ 12 + RJ 22

With TJ the customer has a single pk-pk jitterparameter that correlates to BER (bit errorrate).

TJ incorporates both RJ and DJ in a singlenumber.

Not all vendors have adopted TJ.

SY58011 Datasheet AC Parameters


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SY58011 Datasheet AC Parameters

Jitter Definitions Cheat SheetJitter Definitions Cheat Sheet


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Jitter Definitions Cheat SheetJitter Definitions Cheat SheetJitter Definition

Determinis tic Jitter (DJ):Non-Gaussian PDF and is characterized by it s boundedpk-pk amplitude. There are 2 types:

Periodic Jitter (PJ)

Also known as sinuso idal j it ter

Has a signature that repeats at a fixed frequency

Data Dependent Jitter (DDJ)

Duty Cycle Disto rtion (DCD)

Different rise and fall times andthreshol d variations of a device couldcause DCD.

Intersymbol Interference (ISI)

Occurs when the transmission mediumpropagates the frequency components ofdata (symbols) at different rates.

Random Ji tter (RJ):

Gaussian distributio n and unbounded.

Total Ji tter (TJ):The convolution of allindependent jit ter componentProbability Density Functions(PDF) both determinist ic and

random.

Jit ter Categories

Jitter is the deviation from the ideal timing of an event.

Jitter is composed of both Deterministic and Gaussian(random) content. Total Jitter (TJ) is the convolutionof all independent Jitter Components.

Common Sources of DJTJ

RJDJ

PJ DDJ

ISIDCD

Bounded(Pk-Pk)

Unbounded(RMS)

EMI: Can indu ce noise current in a signalconductor and corrup t the signal by alteringits bias.

Crosstalk: Occurs when the magnetic orelectri c fields of a signal on a conduct or are

inadvertently cou pled to an adjacent signal-carrying conductor, which can slightly alterits bias.

Reflections: Occur when impedancemismatches are present.

RJ eye diagram

DJ eye diagram

Shot Noise: Broadband white noisegenerated when electrons and holes movein a semiconductor . Shot noise amplitud e isa function of average current flow.

Flicker Noise: Proport ional to 1/f. Mostdominant at lower frequencies. Flickernoise is caused by a surface effect due tofluctuations in the carrier density as

electrons are randomly captured andemitted from ox ide interface traps.

Thermal Noise: Can be represented bybroadband white noise, generated by thetransfer of energy between free electronsand ions in a conductor . Unlike shot noise,thermal noise is unrelated to signal currentflow.

Common Sources of RJ

micrel hbw i o structures jitter

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