Designing with Samtec High Speed Cable Assemblies

Microsoft PowerPoint - DESIGNING HS CABLE ASSY REVISED 0606_SM.pptDesigning with Samtec High Speed Cable Assemblies
Designing with Samtec High Speed Cable Assemblies
Samtec High Speed Cable Assemblies Samtec High Speed Cable Assemblies • Agenda
– Background – Why High Speed Cable is Needed – How to Select High Speed Cable – Modeling/Simulation Data – Electrical Test Data – Performance Demonstrations – Correlation between Simulation and Electrical Test Data – Samtec’s High Speed Cable Assembly product offering – Using Samtec’s Cable Builder and Cable Calculator – Samtec’s Signal Integrity Group
Why High Speed Cable is NeededWhy High Speed Cable is Needed • Signal
– Lower cross talk – Lower EMI emission and susceptibility – Higher frequency and less loss – Lower voltage drop
• Mechanical – Challenging mechanical routing – If design is less than 10”, consider flex circuits
Length vs. FrequencyLength vs. Frequency • Single-ended • Flex Assembly, Coaxial Cable Assembly
Fr eq
ue nc
y in
G H
• Things to consider: – Attenuation – DK – Insertion Loss – DCR – Voltage Drop
Cable Selection (Attenuation)Cable Selection (Attenuation)
0 2 4 6 8
10 12 14 16 18 20 22 24 26 28
0.25 0.5 1 1.5
10 12 14 16 18 20 22 24 26 28
0.25 0.5 1 1.5
Fr eq
ue nc
GH z
38 AWG OD = 0.025” 34 AWG OD = 0.04” 30 AWG OD = 0.05” 28 AWG OD = 0.065” 26 AWG OD = 0.075”
Attenuation @ -3dB, Z = 50 or 100 DK = 2.1Attenuation @ -3dB, Z = 50 or 100 DK = 2.1
• Lower DK allows less insulation – Lower tanΔ due to high % of air in dielectric
• Less insulation allows smaller OD: – Can use a larger center conductor – Less insertion loss (due to lower tanΔ)
• Lower DK = more flexibility in length and bandwidth
0.0750 (1.90)0.0750 (1.90)
0.0650 (1.65)0.0650 (1.65)
Cable Selection (Insertion Loss Attenuation)Cable Selection (Insertion Loss Attenuation) • Based on Insertion Loss (dB at frequency) at a specific length
– At a fixed conductor size – If coax / twinax, size is a BIG concern – By decreasing DK, then frequency would increase at a given loss
DK of 2.1, -5dB @ 1.2GHz, C= 29 pF/FT
DK of 1.4, -2dB @ 1.2GHz, C=23 pF/FT
Cable Selection (DC Resistance-Voltage Drop)Cable Selection (DC Resistance-Voltage Drop)
0.00000
0.10000
0.20000
0.30000
0.40000
0.50000
0.60000
0.70000
DCR of Conductors (AWG) Voltage Drop
0.000 0.010 0.020 0.030 0.040 0.050 0.060 0.070
22 24 26 28 30 32 34 36 38
Calculated DCR 12”
Voltage Drop at 12” for various AWG at specific current
.05 Amp
.1 Amp
• Based on Voltage Drop or Ampacity – Increasing Conductor Size AWG
Inside and Outside the BoxInside and Outside the Box
RIBBON TWINAXRIBBON TWINAX
RIBBON COAXRIBBON COAX
ModelingModeling • Complex electromagnetic modeling
is performed on Samtec cables – PCB transitions modeled with CST
Microwave Studio • Accounts for structural discontinuities in
the transition assembly – 2D frequency dependent modeling of
cable performed with Ansoft 2D • Accounts for frequency dependent
characteristics of the cable
interconnect elements is necessary for accurate simulation of systems
– Size matters • The longer an element is, the more important that accurate
frequency dependent modeling is performed – Traces, long connectors, flex, cables ….
» For short, well controlled elements, such as short board- to-board connectors, losses may be ignored with low error
– Irregularity matters • Irregular and 3-dimensional objects generally have non-TEM
propagation modes and require modeling in the frequency domain
– Non-uniform traces, vias, SMA launches, connector transitions, cable transitions, connector breakout regions, antipads ….
TEM Modeling of Uniform StructuresTEM Modeling of Uniform Structures • Uniform long structures may generally be modeled using
TEM or Quasi-TEM assumptions with 2-D field solvers – Traces, coax, some connector cross sections ….
• But error increases if the field solver does not model frequency dependent conductor and dielectric losses correctly – Most do not! – Finite field penetration into conductors (skin effect) is often
only partially modeled. Usually the resistive portion of skin effect is calculated, while the inductive portion is ignored
» Most solvers provide one value for inductance, which is incorrect!
Skin DepthSkin Depth • At high frequencies, most of the current flows
on the surface of conductors • For copper, the skin depth defines the point
at which the magnitude of the field has been reduced by 1/e or 37 percent
MHzin fmicrons,in δ
copperfor , f 1x microns66δ =
Coax Center Conductor Current Distribution - 38 Gauge Coax (4 mil diameter) Coax Center Conductor Current Distribution - 38 Gauge Coax (4 mil diameter)
1 MHz (66 micron) 10 MHz (21 micron) 100 MHz (6.6 micron)
1 GHz (2 micron) 3.5 GHz (1.1 micron)
Frequency Dependence of ResistanceFrequency Dependence of Resistance
DC resistance
AC resistance
Actual resistance values will be strongly dependent upon the conductor cross-section.
Modeled with Ansoft Maxwell 2D
Frequency Dependent Inductance Frequency Dependent Inductance
Modeled with Ansoft Maxwell 2D
External Inductance Asymptote
High frequency surface inductance limit.
Inductance at 350 ps risetime
Variation of inductance in normal operating region is 2% to 3% of extracted value at infinity.
Final Inch® Trace ModelingFinal Inch® Trace Modeling • Our approach to trace modeling
– Utilize Ansoft Maxwell 2D • Finite element quasi-static field solver • Capable of extracting frequency dependent R and L
– Measure (when possible) substrate material properties across frequency (Er and Loss tangent) and use during parameterization
– Extract trace parameters using a parametric sweep • Sweep from 10 Hz to 50 GHz for accuracy across all
frequency bands • Utilize Z and Y matrices
– RLCG matrices do not include losses in Ansoft 2D
– Create HSPICE W-element table model • Automated process to extract Z and Y matrices to create
compatible table model
Snippet of Final W-element Table ModelSnippet of Final W-element Table Model .MODEL final_inch_se W MODELTYPE=table N=1 + RMODEL = final_inch_se_R LMODEL = final_inch_se_L + GMODEL = final_inch_se_G CMODEL = final_inch_se_C
* ###R-model### * data type = * R-model .MODEL final_inch_se_R SP N=1 SPACING=nonuniform VALTYPE=real + INTERPOLATION=spline + DATA=32 * ============= ============= ============= * FREQUENCY: + 0.0000000000000000e+000 * TABLE ELEMENTS: * === row 1 === + 5.1907890527286469e+000 * ============= ============= ============= * FREQUENCY: + 1.0000000000000000e+002 * TABLE ELEMENTS: * === row 1 === + 5.1907890900627756e+000
TEM vs. Non-TEM Modeling Of Non-Uniform Structures TEM vs. Non-TEM Modeling Of Non-Uniform Structures • Non-uniform structures require modeling with a 2.5-D
or 3-D full wave approach – Fields generally do not meet TEM or Quasi-TEM
assumptions • Electric and Magnetic fields are not reasonably orthogonal • Lumped and/or distributed model approximations are no
longer accurate – Network parameters (S-parameters) are generally the
best way to model the broadband performance of these structures
• Full wave field solvers and simulators like CST Microwave Studio can be used for the extraction of these structures
Simulation ModelSimulation Model • EQCD circuit Simulation, 1.0Gbps, 250ps, 6in coax length • ******************************************************************************* • * Copyright 2003, Samtec, Inc. • * • ******************************************************************************* • *!!!!!!!!!! USER INPUT REQUIRED HERE !!!!!!!!!! • * Specify length of coax in inches • .param coax_length_inch = 6 Cable Length • ************************************************ • * convert length to meters • .param coax_length = '(coax_length_inch) * 0.0254'
• .inc './mod/Mqte1qse1.sp‘ Samtec Connector Model
• .inc './inc/Stimulus_se_1bit_prbs3_56rec_1.0Gbps_250ps_50ohm.inc' • .inc 'EQCD-DV_20line_circuit.inc‘ Samtec Cable Model
Correlation to MeasurementCorrelation to Measurement
Measured vs. Modeled IL of 12" Hitachi Coaxial Cable (Vert Scale Changed)
-2
-1.8
-1.6
-1.4
-1.2
-1
-0.8
-0.6
-0.4
-0.2
0
0.00E+00 2.00E+08 4.00E+08 6.00E+08 8.00E+08 1.00E+09
Frequency (Hz)
IL (d
Measured
Modeled
Measurement BoardsMeasurement Boards
Cable AssemblyCable Assembly
Transition Close-upTransition Close-up
• DC Drop
Family of Insertion LossFamily of Insertion Loss
Return LossReturn Loss • Return loss is energy lost due to reflections in the cable
or assembly • Caused by mismatch in impedance
– In the cable • Design • Manufacturing (variance from design, repetitive features) • Handling and installation (kinks)
• Variation due to structural discontinuities is called structural return loss
– Structural return loss happens in: • Transition • Connector • Cable
Return LossReturn Loss
SkewSkew
Skew of cable assemblies should be carefully considered for each application.
Twinax should be used when intra-pair skew of differential pairs is critical.
CrosstalkCrosstalk
Crosstalk of cable assemblies is primarily created within the transition structures.
QTE/QSE 10 Gbps Serdes Demonstration BoardQTE/QSE 10 Gbps Serdes Demonstration Board
Bi-directional transmit and receive boards shown with twinax cable attached
Final Inch® and 1-Meter EQCD Coax, with Accelerant Networks AN6425 PAM-4 Serdes Final Inch® and 1-Meter EQCD Coax, with Accelerant Networks AN6425 PAM-4 Serdes
PAM-4 eye pattern for Accelerant Networks AN6425 at 6.22 Gbps with Samtec QSE/QTE Final Inch® test board and a 1-meter long 38 AWG EQCD micro coax assembly showing excellent eye opening
Boards With 6” Coax With and Without Equalization Boards With 6” Coax With and Without Equalization
PRBS pattern as transmitted through connectors, 6” cable
and PCB only
Equalized
Boards With 0.5 Meter Coax With and Without Equalization Boards With 0.5 Meter Coax With and Without Equalization
Binary eye pattern for MAX3952 PRBS, PCB trace, QTE/QSE connectors, 0.5- meter long 38 AWG EQCD micro coax and MAX3805 adaptive equalizer shows excellent eye opening
1 Meter Coax With and Without Equalization1 Meter Coax With and Without Equalization
Binary eye pattern for MAX3952 PRBS, PCB trace, QTE/QSE connectors, 1-meter long 38 AWG EQCD micro coax and MAX3805 adaptive equalizer
2 Meter Twinax With and Without Equalization2 Meter Twinax With and Without Equalization
PRBS pattern as transmitted through connectors, 2 m twinax and PCB with equalization
Samtec’s Transmission Line OfferingSamtec’s Transmission Line Offering Gauges In Use • 50
– 38 AWG coax – 34 AWG coax – 30 AWG coax – 26 AWG coax
• 100 – 30 AWG twinax – 26 AWG twinax
• Cable produced by Samtec-owned cable manufacturing facility Terabit will be integrated into this available cable offering next quarter
Samtec Data Rate CablesSamtec Data Rate Cables • End-to-End solutions with in-house design and
manufacture of: – High Speed Connectors – High Speed Cable – SI Modeling and Support – Qualification Testing
• “Mix-and-Match” capabilities that include – An extensive line of connectors
• Standard and custom
– A wide variety of cables • Coax and twinax
Signal Integrity SupportSignal Integrity Support Signal Integrity Division
• SI Center: Comprehensive, user-friendly web site for High Speed connector SPICE models, reports, performance data, drawings, searches
• SI Group: Personal, “live person” EE customer interface for application issues
• SI Services: Custom design, modeling, testing of circuits, subsystems, or complete systems
SummarySummary High Speed cable assemblies are a strategic product for Samtec
– Complements High Speed connector offering
– Leverages Samtec’s in-house testing and modeling capabilities
– Samtec is investing significant financial and personnel resources
– High Speed cable solutions plus Samtec’s Sudden Service philosophy are unique
In ClosingIn Closing • For additional questions in regards to our
High Speed cable assemblies, please contact our High Speed Cable Group at: [email protected]
• For a copy of today’s presentation, please contact us at: [email protected]

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Designing with Samtec High Speed Cable Assemblies