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ProjectBackground
DiscontinuityDiscovery
PhysicalTesting
SimulationTesting
Solution
MaterialQualification
Conclusion
Technical Seminar H412
Nanosecond DiscontinuityNanosecond DiscontinuityImpact on Hot-SwapImpact on Hot-Swap
Hank Hank Herrmann Herrmann - AMP- AMPJack Kelly - MotorolaJack Kelly - Motorola
Timothy R. Minnick - AMPTimothy R. Minnick - AMP
2
ProjectBackground
DiscontinuityDiscovery
PhysicalTesting
SimulationTesting
Solution
MaterialQualification
Conclusion
Nanosecond Discontinuities...
...are ...are NOTNOTpin bounce!!!pin bounce!!!
3
ProjectBackground
DiscontinuityDiscovery
PhysicalTesting
SimulationTesting
Solution
MaterialQualification
Conclusion
Session Outline•• Project BackgroundProject Background•• Discovery of the PhenomenonDiscovery of the Phenomenon
–– Physical TestingPhysical Testing
–– Simulation TestingSimulation Testing
•• SolutionSolution•• Material QualificationMaterial Qualification•• ConclusionConclusion
4
ProjectBackground
DiscontinuityDiscovery
PhysicalTesting
SimulationTesting
Solution
MaterialQualification
Conclusion
The Basic System
•• Intense Error-Free Data Rates(telecom)Intense Error-Free Data Rates(telecom)•• Bus ArchitecturesBus Architectures•• Conductive Interfaces (i.e. connectors)Conductive Interfaces (i.e. connectors)•• Hot-Swap CapabilityHot-Swap Capability
Slot 2Slot 1 Slot X
ProjectBackground
5
ProjectBackground
DiscontinuityDiscovery
PhysicalTesting
SimulationTesting
Solution
MaterialQualification
Conclusion
The Hot-Swap System
•• Additional Energy TransferAdditional Energy Transfer•• Additional Signal Integrity RequirementsAdditional Signal Integrity Requirements
Slot 2Slot 1 Slot X
Hot-Swap CardProjectBackground
6
ProjectBackground
DiscontinuityDiscovery
PhysicalTesting
SimulationTesting
Solution
MaterialQualification
Conclusion
Motorola CPX8000 System
•• Telecom Infrastructure ApplicationsTelecom Infrastructure Applications
•• CompactPCI ArchitectureCompactPCI Architecture
•• High AvailabilityHigh Availability
•• Data IntensiveData Intensive
•• Device RedundantDevice Redundant
ProjectBackground
7
ProjectBackground
DiscontinuityDiscovery
PhysicalTesting
SimulationTesting
Solution
MaterialQualification
Conclusion
Detection of a Discontinuity
DiscontinuityDiscovery
8
ProjectBackground
DiscontinuityDiscovery
PhysicalTesting
SimulationTesting
Solution
MaterialQualification
Conclusion
Mechanical Connector Bounce
•• Analyzed at birth of CPCI specificationAnalyzed at birth of CPCI specification
•• Typical speeds in microsecond rangeTypical speeds in microsecond range
•• Pre-charge resistorsPre-charge resistors
Present signal integrity design can not Present signal integrity design can notrespond to nanosecond discontinuities!!respond to nanosecond discontinuities!!
DiscontinuityDiscovery
9
ProjectBackground
DiscontinuityDiscovery
PhysicalTesting
SimulationTesting
Solution
MaterialQualification
Conclusion
Magnified 2mm HM Contact
DiscontinuityDiscovery
10
ProjectBackground
DiscontinuityDiscovery
PhysicalTesting
SimulationTesting
Solution
MaterialQualification
Conclusion
Initial Discontinuity Test Set-Up
PhysicalTesting
Hot-Swap Card
5.0 V
GND
4.7k-Ohm
4.7k-Ohm
Backplane
Scope Probe(1st Channel)
Scope Probe(2nd Channel)
Zoomed-inView (~40 usec)
Engagement
11
ProjectBackground
DiscontinuityDiscovery
PhysicalTesting
SimulationTesting
Solution
MaterialQualification
Conclusion
Electrical Testing
•• Simple voltage dividerSimple voltage divider•• Constant velocity fixtureConstant velocity fixture
Vmeas
PhysicalTesting Oscilloscope
1K
StandardReceptacle
Standard Pin
+5v
12
ProjectBackground
DiscontinuityDiscovery
PhysicalTesting
SimulationTesting
Solution
MaterialQualification
Conclusion
Equipment References
•• Discontinuity DetectionDiscontinuity Detection–– Tektronix TDS 784A Digitizing OscilloscopeTektronix TDS 784A Digitizing Oscilloscope–– Motorola Motorola VxWorks VxWorks Operating SystemOperating System–– Motorola CPX8000 Series Chassis & CardsMotorola CPX8000 Series Chassis & Cards
•• Pin Testing and Resistance ProfilingPin Testing and Resistance Profiling–– Tektronix TDS 684A Digitizing OscilloscopeTektronix TDS 684A Digitizing Oscilloscope–– Mating Fixture with Pneumatic DriveMating Fixture with Pneumatic Drive
PhysicalTesting
13
ProjectBackground
DiscontinuityDiscovery
PhysicalTesting
SimulationTesting
Solution
MaterialQualification
Conclusion
Test Set-Up Results
PhysicalTesting
-1.0
0.0
1.0
2.0
3.0
4.0
5.0
6.0
108.200 108.230 108.260 108.290 108.320 108.350
Time (usec)
Volta
ge (V
)
44ns
-1.0
0.0
1.0
2.0
3.0
4.0
5.0
6.0
0 30 60 90 120 150
Time (usec)
Volta
ge (V
)
Zoom-in Region
14
ProjectBackground
DiscontinuityDiscovery
PhysicalTesting
SimulationTesting
Solution
MaterialQualification
Conclusion
Simulation - CPCI Network
Slot 2Slot 1
1.0 V
Hot-Swap Card
Slot 8
1.0 V
1.0 V
10k-Ohm 10k-Ohm
10k-Ohm
1.5"
1.5"
1.5"
10-Ohm10-Ohm
10-Ohm
0.8"0.8"0.8"
DriverReceiver
SimulationTesting
15
ProjectBackground
DiscontinuityDiscovery
PhysicalTesting
SimulationTesting
Solution
MaterialQualification
Conclusion
Simulation of the Discontinuity
-2.0
-1.0
0.0
1.0
2.0
3.0
4.0
5.0
6.0
0 5 10 15 20 25 30 35 40Time (ns)
Volta
ge (V
)
Driver CardHot-Swap CardReceiver Card
bus signal above receiver threshold
disengagement pointre-engagment point
SimulationTesting
16
ProjectBackground
DiscontinuityDiscovery
PhysicalTesting
SimulationTesting
Solution
MaterialQualification
Conclusion
Simulation Summary
•• Initial point of contact - low normal forceInitial point of contact - low normal force•• Highly conductive interfaceHighly conductive interface•• Microscopic irregularitiesMicroscopic irregularities
A B C
Receptacle Pin
SimulationTesting
17
ProjectBackground
DiscontinuityDiscovery
PhysicalTesting
SimulationTesting
Solution
MaterialQualification
Conclusion
Simulation Conclusions
=> Nanosecond discontinuities=> Nanosecond discontinuities=> Energy transfer onto the bus=> Energy transfer onto the bus
=> Signal Impact=> Signal Impact
Any conductive hot-swap interface!!Any conductive hot-swap interface!!
SimulationTesting
18
ProjectBackground
DiscontinuityDiscovery
PhysicalTesting
SimulationTesting
Solution
MaterialQualification
Conclusion
Solutions
•• Software control during live insertionSoftware control during live insertion
•• Decrease low normal force zoneDecrease low normal force zone
•• Limit rate of energy taken from the busLimit rate of energy taken from the bus–– lower daughtercard capacitancelower daughtercard capacitance
•• physical restructuringphysical restructuring•• impact on signal integrity and timingimpact on signal integrity and timing
–– add resistance during engagementadd resistance during engagement
Solution
19
ProjectBackground
DiscontinuityDiscovery
PhysicalTesting
SimulationTesting
Solution
MaterialQualification
Conclusion
Resistive Pin DevelopmentA B E
Receptacle Pin
C D
Resistive Coating
Unmated Receptacle and Pin
A B E
Receptacle Pin
C DSufficient Normal Force Engagement PositionSolution
20
ProjectBackground
DiscontinuityDiscovery
PhysicalTesting
SimulationTesting
Solution
MaterialQualification
Conclusion
Isolation-to-Resistive Transition
-2.00
-1.00
0.00
1.00
2.00
3.00
4.00
5.00
6.00
0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0Time (ns)
Volta
ge (V
)
Driver CardHot-Swap CardReceiver Card
disengagement pointre-engagement point
gradual release onto backplane
acceptable level
Solution
21
ProjectBackground
DiscontinuityDiscovery
PhysicalTesting
SimulationTesting
Solution
MaterialQualification
Conclusion
Electrical VerificationVDC
VmeasR1
Rtip
MaterialQualification
measdc
meastip VV
RVR-
1∗=
Oscilloscope
1K
StandardReceptacle
ResistiveTip Pin
+5v
22
ProjectBackground
DiscontinuityDiscovery
PhysicalTesting
SimulationTesting
Solution
MaterialQualification
Conclusion
Resistance Profile
MaterialQualification
-0.5
00.5
11.5
2
2.53
3.5
44.5
55.5
6
0 0.5 1 1.5 2Time (msec)
Res
ista
nce
(kO
hms)
Cycle #1
Cycle #100
200-Ohm min
500-Ohm max
23
ProjectBackground
DiscontinuityDiscovery
PhysicalTesting
SimulationTesting
Solution
MaterialQualification
Conclusion
Mechanical Testing
Different Lighting on Magnified Pin - 250 Engagement CyclesDifferent Lighting on Magnified Pin - 250 Engagement Cycles
•• High-cycle durabilityHigh-cycle durability•• Exceptional adhesion to goldExceptional adhesion to gold•• Absence of debrisAbsence of debris
MaterialQualification
24
ProjectBackground
DiscontinuityDiscovery
PhysicalTesting
SimulationTesting
Solution
MaterialQualification
Conclusion
Qualification Testing
•• 2mm HM product spec (108-1622)2mm HM product spec (108-1622)–– 250 cycle durability250 cycle durability–– pin stagingpin staging
•• BellcoreBellcore GR-1217-CORE ( GR-1217-CORE (TelcordiaTelcordia))
•• Resistance requirementsResistance requirementsMaterial
Qualification
25
ProjectBackground
DiscontinuityDiscovery
PhysicalTesting
SimulationTesting
Solution
MaterialQualification
Conclusion
Conclusion - The Problem
-2.0
-1.0
0.0
1.0
2.0
3.0
4.0
5.0
6.0
0 5 10 15 20 25 30 35 40Time (ns)
Volta
ge (V
)
Driver CardHot-Swap CardReceiver Card
bus signal above receiver threshold
disengagement pointre-engagment point
Conclusion
26
ProjectBackground
DiscontinuityDiscovery
PhysicalTesting
SimulationTesting
Solution
MaterialQualification
Conclusion
Conclusion - The Solution
Conclusion
-2.00
-1.00
0.00
1.00
2.00
3.00
4.00
5.00
6.00
0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0Time (ns)
Volta
ge (V
)
Driver CardHot-Swap CardReceiver Card
disengagement pointre-engagement point
gradual release onto backplane
acceptable level
27
ProjectBackground
DiscontinuityDiscovery
PhysicalTesting
SimulationTesting
Solution
MaterialQualification
Conclusion
Conclusion - The Connector
Conclusion
28
ProjectBackground
DiscontinuityDiscovery
PhysicalTesting
SimulationTesting
Solution
MaterialQualification
Conclusion
The Quiet MateTM Contact
Conclusion
29
ProjectBackground
DiscontinuityDiscovery
PhysicalTesting
SimulationTesting
Solution
MaterialQualification
Conclusion
3.3V CPCI System Discontinuity
-1.50
-1.00
-0.50
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0
Time (ns)
Volta
ge (V
)Receiver CardHot-Swap CardDriver Card
disengagement point
re-engagement
bus signal above receiver threshold
30
ProjectBackground
DiscontinuityDiscovery
PhysicalTesting
SimulationTesting
Solution
MaterialQualification
Conclusion
3.3V Quiet MateTM CPCI System
-1.50
-1.00
-0.50
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0
Time (ns)
Volta
ge (V
)Driver CardReceiver CardHot-Swap Card
disengagement pointre-engagement point
gradual release onto backplane
acceptable level
Nanosecond Discontinuities & Quiet MateTM Contacts
1 04/20/00
1 February 10, 2000
The Quiet MateTM Contact
2 February 10, 2000
Nanosecond Discontinuties??
•• Initial Contact Point - Low Normal ForceInitial Contact Point - Low Normal Force
•• Microscopic IrregularitiesMicroscopic Irregularities
•• Highly-Conductive InterfaceHighly-Conductive Interface
•• Different From Pin “Bounce”Different From Pin “Bounce”
A B C
Receptacle Pin
Telecommunications equipment continues todrive faster and faster data rates andbandwidths (levels approaching 1Tbps).These high-speed systems must beextremely reliable and demand that the datathey process meets this level of reliability(five 9’s). Bus-type architectures, includingCompactPCI, provide the backbone for suchsystems. Therefore, bused signal systemsoperating within these requirements mustalso assure that the data they carry is errorfree, even during live insertion operations.During the development and testing of thesesystems, nanosecond discontinuities werediscovered with repeatability. Nanoseconddiscontinuities are electricalconnects/disconnects occurring in the arenaof several nanoseconds to tens and hundredsof microseconds. The electrical disruptionresulting from these intermittencies canadversely affect certain systems.Nanosecond discontinuities occur at theinitial point of closure between two highlyconductive separable interfaces. It isprimarily a result of the microscopic
irregularities and the relative motion of thestructures at the near-zero normal force areaof engagement.Nanosecond discontinuities are differentfrom “pin bounce”, in that they are not amechanical deflection and return of thecontact beam, but rather a result of therelative motion and initial contact of theconductive interface.
3 February 10, 2000
Measured Discontinuity
-1.0
0.0
1.0
2.0
3.0
4.0
5.0
6.0
108.200 108.230 108.260 108.290 108.320 108.350
Time (usec)
Volta
ge (V
)
44ns
-1.0
0.0
1.0
2.0
3.0
4.0
5.0
6.0
0 30 60 90 120 150
Time (usec)
Volta
ge (V
)
Zoom-in Region
Nanosecond discontinuities are extremelydifficult to capture with consistency. Anextensive understanding of the system andhow it responds to a live insertion event iscritical in detecting the phenomenon.Advanced (and expensive) test probes,measurement scopes, and specialized testfixtures aid in the identification of theintermittencies.Data samples from one such test set-up areclear enough to discern the fasterdisruptions, due to the optimally reducedtime constant of the test-bed. The measuredwaveforms were plotted on a voltage scaleto 5V against a physical engagement time-scale. The recorded data is then focused onthe specific areas around the transition edgesof engagement and disengagement.The measured waveform displaysintermittencies detected during a cardengagement event. When the irregularitiesare magnified [seen as the waveform on theright], a discontinuity of approximately 44nanoseconds is measured.The intermittencies are extremely erratic andvary anywhere from 100’s of microsecondsto single digit nanoseconds. The
Nanosecond Discontinuities & Quiet MateTM Contacts
2 04/20/00
phenomenon has been detected during bothengagement and disengagement operations.
4 February 10, 2000
Susceptible Systems
•• Bus ArchitecturesBus Architectures•• Hot-Swap CapabilityHot-Swap Capability•• High Fault-Tolerance RequirementsHigh Fault-Tolerance Requirements
Slot 2Slot 1 Slot X
Hot-Swap Card
Specific systems which are susceptible tonanosecond discontinuities are those whichhave a ‘bused’ or ‘multi-drop’ architecture,and possess the capability of hot-swappingcards. An operating system requires that atleast one card is present and ‘driving’, witha second (or additional) card(s) ‘receiving’,when a third card is inserted into the system.Typically, systems which require high fault-tolerance operation will be more affected bynanosecond discontinuities (as theintermittencies tend to adversely impactsystems on a relatively infrequent basis).
5 February 10, 2000
Hot-Swap System Diagram
BusDriver
Receiver Card
Hot-Swap Card
Pre-ChargeEstablished
1st Contact 1st Break 2nd Contact
NanosecondDiscontinuity Event
DataTransition
A simple timing diagram best illustrates theworst-case impact of a nanoseconddiscontinuity:- At first contact between a hot-swap cardand the backplane, all waveforms coincide(including the hot-plugged card), as allpieces are connected electrically andrunning.
- At the first break point (or beginning of thenanosecond discontinuity), the hot-swapcard electrically separates from the runningbus, and continues to hold the energy it hadwhen the separation occurred. This energywill leak off as a result of pre-charge orother termination devices, but it is typicallysubject to extremely slow time constants, asa result of the high resistance valueassociated with pre-charge elements.- During the nanosecond discontinuity event,the backplane bus may switch logic levels(in the example, the bus transitions fromhigh to low). High-speed drivers will allowthis transition to occur as quickly as 1-2nanoseconds, or possibly faster.- Shortly after the bus transition, thenanosecond discontinuity ends, and the hot-swap card comes back in electrical contactwith the backplane bus. Two separatevoltage potentials come together at onepoint.- As a result, energy will immediately betransferred to/from the daughtercard,depending on relative potentials. Thisenergy transfer has the capability ofimpacting a received/sampled signalwaveform significantly enough to result infalse data transfer.
6 February 10, 2000
Detection of the Discontinuity
-2.0
-1.0
0.0
1.0
2.0
3.0
4.0
5.0
6.0
0 5 10 15 20 25 30 35 40Time (ns)
Volta
ge (V
)
Driver CardHot-Swap CardReceiver Card
bus signal above receiver threshold
disengagement pointre-engagment point
An actual system waveform plot displays theimpact of a nanosecond discontinuity on asampled waveform. The additionaltransferred energy boosts the level of thesignal above the threshold of the receiver(blue line), and could result in a falsesampling of data.
Nanosecond Discontinuities & Quiet MateTM Contacts
3 04/20/00
7 February 10, 2000
Nanosecond Discontinuity Impact
=> Nanosecond discontinuities=> Nanosecond discontinuities=> Energy transfer onto the bus=> Energy transfer onto the bus
=> Signal Impact=> Signal Impact
Any conductive Any conductivehot-swap interface!!hot-swap interface!!
Simulation and testing of hot-swap networkshas shown that nanosecond discontinuitiesresult in energy transferred onto or out of thebus. Additional energy transferred to anactive bus has the potential of altering signallevels. (Existing pull-up terminations areineffective during a nanoseconddiscontinuity, due to their relatively slowtime constants.) Nanosecond discontinuitiescan occur at any conductive hot-swapinterface at the near-zero normal force zonethat occurs at the very beginning ofengagement.
8 February 10, 2000
Solutions
•• Software control during live insertionSoftware control during live insertion
•• Decrease low normal force zoneDecrease low normal force zone
•• Limit rate of energy taken from the busLimit rate of energy taken from the bus–– lower daughtercard capacitancelower daughtercard capacitance
•• physical restructuringphysical restructuring•• impact on signal integrity and timingimpact on signal integrity and timing
–– add resistance during engagementadd resistance during engagement
Solutions to nanosecond discontinuities cantake several forms. The situation can becontrolled through software or hardware.Software solutions are possible, but slow theoverall response of the system, thus ahardware solution that does not slow thesystem is preferred.A decrease in the time of low normal forcemating would help to minimizediscontinuities. Stiffening backplanes andpre-loading spring members help to decrease
the amount of time that the phenomenon canexist and would reduce the probabilities of asystem detecting discontinuities. However,since there is always an initial point ofcontact, and since the inconsistencies occuron the molecular level, probabilities aredecreased but not eliminated.The final option is to limit the amount ofenergy the daughtercard injects/absorbsto/from the bus when the two metal surfacesmake electrical contact. One way ofapproaching this is to lower the capacitanceon the daughtercard as much as possible.Minimization of contact pads and othermetallic structures will reduce thiscapacitance and effectively make thedaughtercard more inductive. However, thisreduction in capacitance can have an ill-effect on the loading and timing of the bus,especially since the reduction must occur onall cards. In addition to signal integrityconcerns, the reduction in capacitance stillmay not guarantee that the energy flow willbe reduced to an acceptable level. Thesecond option to reducing energy flowduring the mating sequence is to create aresistive “shock absorber” between thereceptacle contact and the header pin, untilan acceptable normal force can beestablished. This resistance would then beinvisible to an operating system (followingthe live insertion event).
9 February 10, 2000
Resistive Application
Receptacle Pin
Resistive Coating
Unmated Receptacle and Pin
Receptacle Pin
Final Engagement Position
The requirement of a guaranteed error-freelive insertion points to the application of aresistive material on the pin as the bestsolution. The material must exist on aspecific region of the pin. The material
Nanosecond Discontinuities & Quiet MateTM Contacts
4 04/20/00
must exist on the tip of the pin in any areawhere the pin and receptacle could possiblymake first contact. The material must alsoextend back far enough on the pin to assurethat sufficient normal force is obtained priorto the receptacle sliding to and makingdefinitive contact with the gold surface ofthe pin. Sufficient normal force guaranteesthat the receptacle contact will not loseelectrical contact with the resistive materialor gold finish. The final resting position ofthe pin is noted by the vertical dashed line.
10 February 10, 2000
System Diagram Improved
BusDriver
Receiver Card
Hot-Swap Card
Hot-Swap Card &Quiet Mate Contacts
Pre-ChargeEstablished
1st Contact 1st Break 2nd Contact
NanosecondDiscontinuity Event
DataTransition
& Quiet Mate Contacts
An adjusted timing diagram displays thenew behavior of a hot-swapped card, and theresulting energy response seen at the inputof a sampling receiver device, when theresistive pin tip is used. The total amount ofenergy transferred is the same as before,however the rate at which it is transferred ismuch different. The reduced transfer rateprovides an impact at the receiver that nolonger can result in a false sampling of thewaveform data.
11 February 10, 2000
The Solution
-2.00
-1.00
0.00
1.00
2.00
3.00
4.00
5.00
6.00
0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0Time (ns)
Volta
ge (V
)
Driver CardHot-Swap CardReceiver Card
disengagement pointre-engagement point
gradual release onto backplane
acceptable level
Electrical simulations provide waveformsshowing an actual bus signal’s response to alive insertion event, with the resistivematerial present on the tip of the pin. Theresulting rate of current into the backplanenetwork is not enough to force thecontinuously running data bus to cross thethresholds of the detecting receiver.
12 February 10, 2000
Qualification Testing
•• 2mm HM product spec (108-1622)2mm HM product spec (108-1622)–– 250 cycle durability250 cycle durability–– pin stagingpin staging
•• BellcoreBellcore GR-1217-CORE ( GR-1217-CORE (TelcordiaTelcordia))–– Mixed Flowing Gas (MFG)Mixed Flowing Gas (MFG)–– Temperature/HumidityTemperature/Humidity
•• Resistance requirementsResistance requirements
The new resistive material has been tested tothe 2mm HM product specification (108-1622) and qualified to the Bellcore GR-1217-CORE (Telcordia) specification. Thepin continues to meet all specifications. Thedurability of the new material exceeds thealready high (250 cycle) productrequirement. Pin staging requirementscontinue to provide sequential mating, dueto the location of the resistive material. Thematerial is also being qualified, throughresistance profiles, to the required resistanceranges specified by the simulations andverification testing.