DensiShield Cable Assembly. InfiniBand Standard CX4 Standard

Transcription

1 DensiShield Cable Assembly InfiniBand Standard CX4 Standard SI Revision 1 August

2 Introduction The purpose of these tests was to show compliance of FCI s 26 AWG DensiShield cable assemblies to the InfiniBand Architecture Release and the 802.3ak-2004 (CX4) requirements. Measurement parameters Impedance Insertion Loss Return Loss Time-Domain Multi-Active Near-End Crosstalk Frequency-Domain Single-Active and Multi-Active Near-End and Far- End Crosstalk Pair to pair skew Eye Pattern Jitter, Eye height, and Eye width Equipment Used Digital Sampling Oscilloscope Tektronix CSA 8000B 4-port VNA (HP8720ES and ATN-4112A S-parameter test set) Pulse Pattern Generator D3186 Advantest and HP8133A 2

3 Test boards and assembly wiring Test board was used to complete the required testing. These 4-layer boards have all 8 differential pairs routed with trace lengths of 42mm and trace widths of 0.30mm). Cable assemblies tested were FCI base part number DensiShield Test Board P/N DensiShield receptacles P/N LF Measurement Set-up Stackup 3

4 Differential Impedance The differential impedance was measured using a CSA8000B Digital Sampling Oscilloscope. The data was measured at 50 ps (20-80%) risetime and filtered to the InfiniBand Architecture Release required 100 ps (20-80%). The following impedance profiles represent the expected impedance for the DensiShield cable assembly. Densi-Shield Differential Impedence Risetime 100ps (20-80%) Upper Limit 105 Ohms Lower Limit 85 Time 500ps/div 4

5 Differential Insertion Loss The differential insertion loss of the cable assemblies was measured with an HP8720ES/ATN-4112A 4-Port Network Analyzer (according to the InfiniBand and CX4 specifications.) The loss results of the connector and cable compared to the InfiniBand and CX4 insertion loss requirements are shown below. 0 Differential Insertion Loss with the PCB loss removed 1 meter data -5 3 meter data 5 meter data Differential Insertion Loss (db) -10 SDR Limit CX4 Limit DDR Limit QDR Limit 12 meter data Frequency (GHz) 5

6 Typical Differential Return Loss The differential return loss of the cable assemblies was measured with an HP8720ES/ATN-4112A 4-Port Network Analyzer (according to the InfiniBand and CX4 specifications.) The reflection results compared to the InfiniBand and CX4 return loss requirements are shown below. 0 DensiShield Differential Return Loss Differential Return Loss of ALL Cables -10 SDR Limit DDR Limit QDR Limit CX4 Limit Differential Return Loss (db) Frequency (GHz) 6

7 Differential Crosstalk Time-Domain crosstalk measurements were taken with a CSA 8000B Digital Sampling Oscilloscope. Frequency-Domain crosstalk measurements were taken with an HP8720ES/ATN-4112A 4-Port Vector Network Analyzer. Near-end measurements were performed with TX1, TX2, TX3, and TX4 active and listening to RX2 and RX3. Far-end measurements were performed listening to RX2 and exciting pairs TX1, TX3, and TX4. Time domain measurements were taken at 50 ps (20-80%) as required by the double data rate InfiniBand specification. The expected multi-active time-domain crosstalk result for the DensiShield cable assembly is less then 1.5%. The InfiniBand specification for timedomain near-end crosstalk is 4%. Both the expected frequency-domain single active and multi-active results are shown on the following slides. The red curve ending at 2 GHz in each of the graphs shows the CX4 requirement. Transmitting Pairs Receiving Pairs A A A A B B B B G G G G D D D D E E E E Connector Configuration 7

8 Frequency Domain Crosstalk results Differential Equal Level (Single Active) Near-End Crosstalk Differential Multiple Disturber (Multi-Active) Near-End Crosstalk Crosstalk (db) CX4 Limit Crosstalk (db) CX4 Limit Frequency (GHz) 0 Differential Equal Level (Single Active) Far-End Crosstalk Frequency (GHz) 0 Differential Multiple Disturber (Multi-Active) Far-End Crosstalk CX4 Limit CX4 Limit Crosstalk (db) Crosstalk (db) Frequency (GHz) Frequency (GHz) 8

9 Inter-Pair Skew The skew between each of the 8 differential pairs for 4 different cables is shown below. The pair to pair skew was measured with a CSA 8000B Digital Sampling Oscilloscope. The measurement was performed by saving the TDT step of the calibration trace of the test board as a reference and measuring the delay between the reference and the TDT step of each differential cable pair. The delay of each differential pair is shown below. The maximum and the contributing pairs to the maximum skew value are highlighted in grey. All cables met the maximum skew specification of 500 ps from InfiniBand The skew data below is representative of the raw cable used in DensiShield assemblies. Inter-Pair Skew Cable 3 Cable 5 Cable 8 Cable 10 Max (ps): Delay with respect to calibration traces (ns) SA P SB P SA P SB P SA P SB P SA P SB P

10 Eye Pattern / Jitter The following eye patterns present a visual representation of the effect that the DensiShield cables have on an actual data stream. These measurements were obtained using an Advantest D Gbps Pattern Generator, two Agilent 8133A 3Gbps Pulse Generators, and a Tektronix CSA 8000B Digital Sampling Oscilloscope. A differential Fiber Channel CJPAT data pattern was used to excite pair DE2. For the three far-end adjacent transmit pairs (AB1, AB3, and AB4), an asynchronous 32-bit PRBS pattern was driven at the same frequency as the data rate, except for the double and quad data rates (5.0/10 Gbps), where the adjacent signal was driven at 3.5 GHz. The acquisition condition was hits in an equivalent 20 mv high jitter box per InfiniBand InfiniBand denotes the minimum eye height at 196 mv and eye width at 0.75 UI, seen in Figure 13 as the diamond shaped mask 1 (pink). The InfiniBand specification also requires a 20 mv high equivalent jitter box. 10

11 Reference Eye Pattern and Jitter results SDR 2.5 Gbps Calibration Trace Jitter 10 ps DDR 5 Gbps Calibration Trace Jitter 11ps QDR 10 Gbps Calibration Trace Jitter 9 ps 11

12 Sample Eye Pattern and Jitter results SDR 2.5 Gbps 5 meter Jitter = 60 ps Criterion = 100 ps DDR 5 Gbps 3 meter Jitter 40 ps Criterion = 50 ps QDR 10 Gbps 1 meter Jitter 21 ps Criterion = 25 ps 12

13 Conclusion CX4 longest compatible length is 12 meters Single Data Rate InfiniBand longest compatible length is 5 meters Double Data Rate InfiniBand longest compatible length is 3 meters Quad Data Rate InfiniBand longest compatible length is 1 meter 13