M. Lindgren October 5, 2001CMS EMU Meeting -1ALCT-TMB Cable

Comparisons

2 companies expressed interest in supplying a cheaper cable than the Amphenol Skewclear.TYCO – sent two pieces of cable to UCLA3M – Had meeting with them, and they apparently decided

that they were uninterested

TYCO cablesSumitomo, 12 meter, halogen, 30 gauge individual pairsMadison, 10.5 Meter, halogen free, 28(?) gauge individual

pairs.- No individual pair shielding on either cable, just an overall one.

M. Lindgren October 5, 2001CMS EMU Meeting -2

Cable tests

Initial tests used OSU cable tester, and both cables passed walking ones and zero’s tests, and also a pseudorandom one at 80 Mhz. Could not look at signals with a scope as board was too noisy.

Built a small board with just 2 lvds drivers to look at individual signals for skew and rise time, etc.

Also had one FAST site Skewclear cable(failed the first tester) for comparison.

M. Lindgren October 5, 2001CMS EMU Meeting -3

Skewclear – LVDS signals

LVDS driven down on pair and terminated into 100 Ohms.

Signal measured using FET probe and Tek scope

M. Lindgren October 5, 2001CMS EMU Meeting -4

Madison – LVDS signals

Same driver into the Madison cable

Signal shape and attenuation is similar to Skewclear

M. Lindgren October 5, 2001CMS EMU Meeting -5

Sumitomo – LVDS signals

Same driver into Sumitomo cable

Much worse than the other two

M. Lindgren October 5, 2001CMS EMU Meeting -6

Skewclear – Pair to pair

Used two drivers, then compared arrival times at termination resistors

Largest difference measured was .3 ns

Actual skew probably less, as were close to limit of ability to measure on scope

M. Lindgren October 5, 2001CMS EMU Meeting -7Skewclear – Pair to Pair

Skew

0

0.1

0.2

0.3

0.4

0.5

0.6

1 3 5 7 9 11 13

15

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23

Series1

Pair #

ns

M. Lindgren October 5, 2001CMS EMU Meeting -8

Madison – pair to pair

This is one of the better pairs.

Max difference between any two pairs was 1.1 ns

M. Lindgren October 5, 2001CMS EMU Meeting -9Madison – pair to pair

skew

0

0.2

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0.6

0.8

1

1.2

1.4

1.6

1 3 5 7 9 11 13

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Series1

Pair #

ns

M. Lindgren October 5, 2001CMS EMU Meeting -10

Sumitomo – pair to pair

Sumitomo cable skew was about the same as the Madison, max difference between pairs was 1.2 ns

M. Lindgren October 5, 2001CMS EMU Meeting -11Sumitomo – Pair to Pair

Skew

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1.2

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25

Series1

ns

Pair #

M. Lindgren October 5, 2001CMS EMU Meeting -12

Skew within pairs

Skewclear was hard to measure, as it was again vary small compared to the other two.

Madison maximum skew within a pair was .9 ns

M. Lindgren October 5, 2001CMS EMU Meeting -13

Mad. – Skew within pairs

0

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1

1.2

1 3 5 7 9 11 13

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25

Series1

Pair #

ns

M. Lindgren October 5, 2001CMS EMU Meeting -14

Conclusions

Neither cable met the spec that the maximum pair to pair skew be < 1 ns.

The Madison cable signal attenuation was much less than the Sumitomo, and the signal shape was comparable to the Skewclear.

The quoted price for long Madison cables from TYCO was $239/cable. If the Skewclear is much more expensive than this, we should have TYCO construct some actual cables using this cable and the proper connectors and backshells to evaluate at the FAST sites.

Otherwise, the Skewclear is clearly superior to the TYCO cables, and should be used if it can be purchased for about the same money.