January 30, 2002 Slide 1 of 24 H19- Reliable Serial Backplane Data Transmission at 10 Gb/s
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
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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
-15
-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) [email protected]
• Michael Fogg(717) [email protected]
• Ken Lazaris-Brunner(905) 632-2999, ext. [email protected]
• Bharat Tailor(905) 632-2999, ext. [email protected]
Demonstration at Tyco Electronics DesignCon Booth #942