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Cables (/connectors) zSignal inventory ysignal types / characteristics yextra signals of pile-up zTypes of cables ytwisted pair vs. striplines yCable test.

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Presentation on theme: "Cables (/connectors) zSignal inventory ysignal types / characteristics yextra signals of pile-up zTypes of cables ytwisted pair vs. striplines yCable test."— Presentation transcript:

1 Cables (/connectors) zSignal inventory ysignal types / characteristics yextra signals of pile-up zTypes of cables ytwisted pair vs. striplines yCable test zOther (open) issues ygrounding & shielding ybuffering on flange

2 Scta beetle Optional buffer Receiver in racks 1.. 2 meter10.. 15 meter vacuum air unshieldedshielded

3 Signal inventory zLow voltage power lines zAnalog outputs zDigital control (lvds / cmos) zDigital outputs (lvds, pile-up only) zOther signals ydetector bias ytemperature sensors

4 Low voltage power zSimple calculation: y1/2 wheel = 16 frontend chips y16 * 500 mW = 8 Watts yIf Vdd = 2.5 volts => I= 3.2 Amp zCopper area needed > 1 mm 2 ycooling? y1 meter = 170 mW

5 Analog output signals zBalanced output pair yfew hundred millivolts for 10 Mip signal yBandwidth >> 40 MHz ysensitive to pickup z4 pairs per frontend chip

6 Digital control lines zLVDS (low voltage differential signalling) yclock, trigger, reset yfrequency: 40 MHz yline termination needed yclock / trigger per 4 / 8 / (16) chips zCMOS-level yI 2 C interface ylow frequency yline termination optional (series termination) yone set of signals for 1/2 wheel?

7 LVDS Driver: 250 mV into 100 ohms Receiver: 100 mV differential Maximum cable attenuation = 8 dB (Z 0 = 100 ohms)

8 Digital outputs zPile-up comparator outputs zLVDS @ 80 Mbit y16 pairs per frontend chip, 256 for 1/2 wheel yextra connectors on hybrid needed

9 Other signals zBias for detector yhigh voltage, upto 500 Volts ? ylow current zTemperature sensors yspecification depends on sensor type yno-high speed, low current… y1 sensor for 1/2 wheel

10 Summary

11 Cable requirements zvacuum compatible zradiation hard zmoderate signal loss zflexible zthin zcharacteristic impedance of 100 ohms zpolyimide (kapton) isolation

12 Cable “specifications” zCable impedance ygeometry ydielectric constant of isolation (~ 3) zLoss yDC resisitive loss ylosses due to skin effect, proximity effect ydielectric loss zDispersion

13 Cable losses Wire resistance ~1.7  per meter for 0.01 mm 2 Skin depth ~10  m @ 40 MHz Dielectric loss low for good dielectrics dispersion

14 Example zDiameter 0.1 mm yRdc = 1.3  / m yskin loss @ 40 Mhz adds a factor 2.5 y~20% signal loss for 2 meter zsame copper area for stripline (35  m Cu) ywidth = 0.225 mm yskin loss @ 40 Mhz adds a factor 1.5 y~13 % signal loss for 2 meter

15 Impedance of cable D d For kapton Z0 ~ 100 ohms if D = 2*d Twisted pair h wsw Microstrip line See figure

16 Grounding /shielding zQuestions yCentral (star) ground, where yshielded cables upto flange yvacuum cables run close to machine ground

17 Buffering zRad-hard components zcooling problem


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