H19- Reliable Serial Backplane Data Transmission at 10 Gb/s · transmission media selection....

January 30, 2002Slide 1 of 24

H19- Reliable Serial Backplane Data Transmission at 10 Gb/s

January 30, 2002Slide 2 of 24

Board InterfaceHigher Performance MediaAlternate Drilling P

assive

Passive

Board InterfaceHigher Performance MediaAlternate Drilling

Semiconductors

EqualizationPre-emphasis

Encoding Techniques

ChannelArchitectureConnectorsTransmission Media

Loss PropertiesLengthConstruction

Evolution of the Interconnect

LengthLength

FFrreeqquueennccyy

Active

A

c

t

i

v

e

January 30, 2002Slide 3 of 24

Transmission over Media Only

-The output waveforms shownresult from a 1-volt, 32-bitinverting K28.5 input bitpattern (10 Gbps, 60psedges) that is applied to a12 mil, 50 Ohm striplinetrace that is 18” long.

FR4Jitter = 0.30 UIOpening = 238 mV

FR4:FR4

Jitter = 0.30 UIOpening = 238 mV

FR4:GETEK

Jitter = 0.28 UIOpening = 268 mV

GETEK:

GETEK

Jitter = 0.28 UIOpening = 268 mV

GETEK:

ROGERS 4350

Jitter = 0.20 UIOpening = 426 mV

ROGERS 4350:

ROGERS 4350

Jitter = 0.20 UIOpening = 426 mV

ROGERS 4350:

ARLON CLTE Jitter = 0.19 UIOpening = 520 mV

ARLON CLTE:ARLON CLTE Jitter = 0.19 UI

Opening = 520 mV

ARLON CLTE:

January 30, 2002Slide 4 of 24

Transmission over Media Plus Two Connectors

January 30, 2002Slide 5 of 24

The Connector / Board Interface

connector pin

layer connection

“TOP” layer connection

“BOTTOM” layer connection

January 30, 2002Slide 6 of 24

Z-PACK HM-Zd Evaluation System

• System Environment using FR-4 (Nelco 4000-6)• Backplane – 0.200” Line Card – 0.115”• Different system lengths - 10”, 22” and 30”• Various trace widths• No counterboring

January 30, 2002Slide 7 of 24

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

1.0E+08 1.0E+09 1.0E+10FREQ (Hz)

SDD

21 (d

B)

10 Inches 22 Inches 30 Inches

Performance Comparison – Bottom Layer

Daughtercard Trace Width – 0.005”

Line Card Trace Width – 0.012”

January 30, 2002Slide 8 of 24

Performance Comparison – 30 Inches

Daughtercard Trace Width – 0.005”

Line Card Trace Width – 0.012”

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

1.0E+08 1.0E+09 1.0E+10FREQ (Hz)

SDD

21 (d

B)

Top Bottom Near-top Near-bottom

January 30, 2002Slide 9 of 24

-50

-45

-40

-35

-30

-25

-20

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-10

-5

0

1.0E+08 1.0E+09 1.0E+10FREQ (Hz)

SDD

21 (d

B)

Bottom Layer - 30 Inches Top Layer - 22 Inches

Trace Length is NOT the Only Issue

Daughtercard Trace Width – 0.005”

Line Card Trace Width – 0.012”

January 30, 2002Slide 10 of 24

Cable Insertion Loss(With/Without Connectors)

SDD

21 (d

B)

January 30, 2002Slide 11 of 24

Resonance Test System

• Similar to HM-Zd Evaluation System• Backplane traces replaced with low

loss cable– Minimize loss in system– Investigation of resonance effects– Same daughtercard as HM-Zd Evaluation

System

January 30, 2002Slide 12 of 24

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

1.0E+08 1.0E+09 1.0E+10FREQ (Hz)

SD

D21

(dB

)

Non-optimized Optimized

Reducing The Top Layer Effect

Driven by connector characteristics and design. No counterboring done on 0.200” backplane.

January 30, 2002Slide 13 of 24

Channel Conclusions• Easy to see channel optimization in frequency domain • Layer connection determines performance

– “Top” ⇒ unpredictable– “Bottom ⇒ predictable

• Magnitude of discontinuity effect increases with frequency• Unpredictable losses at higher frequencies can negate

improvements in channel performance – Shorter system lengths– media selection

• Optimization of unpredictable losses, i.e. top layer effect, appears possible

• Improvement of predictable losses gained through better transmission media selection

January 30, 2002Slide 14 of 24

Channel Attenuation

Source Equalizer

25m 50m 75m 100m 125m 150m 175m

Belden 1694A Coaxial Cable

lfkfjlk dselfC −+−= )1(),(

January 30, 2002Slide 15 of 24

Adaptation Algorithm

• Signal transmitted with well-defined amplitude– spectral content at specific frequency allows

estimation of attenuation• Attenuation estimate used to control

inverse transfer function magnitude– shape is fixed

• Same methodology can be applied to traces

January 30, 2002Slide 16 of 24

Adaptive Equalizer Advantages

• Can apply a lot of gain– Have applied up to 30 dB

• Wide range of attenuation characteristics with no adjustment

• Can handle wide range of data rates with no adjustment

• Fast adaptation with no training sequence• Reliable convergence even with no eye present

January 30, 2002Slide 17 of 24

Post-equalizer Additive Jitter Sources

• Errors in adaptation• Difference between trace attenuation

characteristics and device frequency gain• Above two sources can be reduced to

0.2UI additive jitter• Ripples in channel attenuation due to

reflections can be more serious

January 30, 2002Slide 18 of 24

Increased Jitter Due to Channel Loss Ripple

January 30, 2002Slide 19 of 24

Conclusions

• Equalizer will flatten channel– ripple effects are independent of trace length up to

equalizer maximum• Generally ripple in frequency range below

half the data rate is most significant– ripple above fundamental frequency will have

smaller effect• Implication

– Good backplane design is required for equalizer work to maximum potential

January 30, 2002Slide 20 of 24

Z-PACK HM-Zd Evaluation System

January 30, 2002Slide 21 of 24

10.7 Gb/s Eye Diagrams after GN2001

Trace-only - 25”

Bottom-Layer Connection - 22”

Top-Layer Connection - 22”

January 30, 2002Slide 22 of 24

Summary of Testing

Length Layer Connection

Section 1 (8/12)*

Section 2 (5/12)*

Section 3 (5/8)*

22 inches 1 (top) 7 Gb/s 7 Gb/s 7 Gb/s2 9 Gb/s 9 Gb/s 9 Gb/s3 11 Gb/s 11 Gb/s 11 Gb/s

4 (bottom) 12 Gb/s 12 Gb/s 12 Gb/s

30 inches 1 7 Gb/s 7 Gb/s 7 Gb/s2 8 Gb/s 8 Gb/s 7 Gb/s3 9 Gb/s 8 Gb/s 8 Gb/s4 10 Gb/s 10 Gb/s 10 Gb/s

Note – Speed based on observed 50% eye* - first number denotes daughtercard trace width in mils

second number denotes backplane trace width in mils

January 30, 2002Slide 23 of 24

Active Cable Assembly in PT Module

January 30, 2002Slide 24 of 24

10.7 Gb/s over 10m of 22 AWG Differential Cable with HSSDC2 Connectors

January 30, 2002Slide 25 of 24

Test Conclusions• For backplanes

– Ability to support 10 Gb/s data rates is layer connection driven.

– Rate ability degrades as layer connection moves towards top of board.

– Proper channel design can support 10.7 Gb/s operation @ 22 inches over FR-4 (Nelco 4000-6)

• For cables– Ability to support 10 Gb/s data rates is limited by

quality of cable assembly– Refinement in connector design and equalization

will increase transmission length

January 30, 2002Slide 26 of 24

Conclusion

Successful transmission of data rates at 10 Gb/s and above is a synergistic issue between channel design (architecture, component selection and implementation) and active device techniques.

January 30, 2002Slide 27 of 24

For Further Information

• John D’Ambrosia(717) 986-5692john.dambrosia@tycoelectronics.com

• Michael Fogg(717) 986-5802mike.fogg@tycoelectronics.com

• Ken Lazaris-Brunner(905) 632-2999, ext. 3016ken_la@gennum.com

• Bharat Tailor(905) 632-2999, ext. 3340bharat_t@gennum.com

Demonstration at Tyco Electronics DesignCon Booth #942