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CMS FED Testing

CMS FED Testing. Update 28-06-2002 M. Noy & J. Leaver Imperial College Silicon Group. DAC Evaluation board. LVDS. UTP. LVTTL. SEQSI. UTP. VME. Opto-Tx. I2C control. I2C master. Optical Fibre. 8 bit oscilloscope. Coax. Opto-Rx. GPIB. PC. CMS FED Testing. Currently:.

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CMS FED Testing

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  1. CMS FED Testing Update 28-06-2002 M. Noy & J. Leaver Imperial College Silicon Group

  2. DAC Evaluation board LVDS UTP LVTTL SEQSI UTP VME Opto-Tx I2C control I2C master Optical Fibre 8 bit oscilloscope Coax Opto-Rx GPIB PC CMS FED Testing Currently: Line driver + (optional) level shift LVDSLVTTL I2C slave Network

  3. CMS FED Testing Picture of the DAC evaluation board DAC Line driver LVTTL data in, from level converter UTP out

  4. CMS FED Testing Picture of the key link components UTP from DAC/line driver Optical fibre Opto-Tx Opto-Rx Single ended output to scope I2C cable

  5. 10111011010 1 scope CMS FED Testing Opto-Tx DAC Evaluation Board Line driver UTP DAC UTP Opto-Rx Vout

  6. CMS FED Testing Signal before the link 200mV (V+-V- =400mV) differential signal with no offset. higher bandwidth  ringing and faster rise/fall time. Time scale is relative to the scope trigger point on all plots.

  7. CMS FED Testing Signal after the link Single ended, with offset. No ringing but slower rise/fall times

  8. CMS FED Testing Signal noise/jitter after the link Note:no scale on the width of the line. This is an impression of the infinite persistence scope trace => spread unknown. (Measurements are real).

  9. CMS FED Testing Rise time, 10% to 90% of full scale.

  10. CMS FED Testing Fall time 90% to 10% of full scale

  11. CMS FED Testing Linearity: link is being operated in the linear region of the Tx/Rx Settings: x0, x1, x2, x3, x4, x5=0,0,0,0,1 (recommended by CERN) 000 01

  12. CMS FED Testing Sample APV25 pair of multiplexed frames with simulated 1 MIP signal

  13. CMS FED Testing Multiplexed APV25 header with zero pipeline address 2 error bits pipeline address (16 bits) 2x12x25ns bits = 6 start bits

  14. CMS FED Testing Zoom in of the 1 MIP signal upon its pedestal • Approx: • Pedestal value here is 509 lsbs, 4096 levels in 405mV0.099mV/lsb • 1 MIP  4096/8=512 lsbs • Total signal =570+(405/4096)*(509+512)=570+0.099*1021=671mV

  15. CMS FED Testing Temperature Control We attached a heating element and a thermocouple to the laser package and used the following PID equation to stabilise the temperature through a feedback loop. W = P [ (Ts - T0) + D d (Ts- T0) /dt + I  (Ts - T0)dt] The temperature was varied between 30ºC and 40ºC in ~1ºC steps. The output of the Rx was recorded after a stabilisation time, for some measurement time.

  16. CMS FED Testing Temperature Measurements Laser threshold bias current behaves like Ith=I0exp(T/T0) Which implies IthIthT/T0 And (after a few lines and other things!) Vout  -Reff G Rx l Ith T/T0 Typical parameter values yield an expected (@ 34.1°C) Vout/T -90.8 mV/°C

  17. CMS FED Testing Temperature Measurement Results Approximated with a linear fit V=mT+C Where m = -(89.8  1.8) mV/°C and C = (4137  62) mV Good agreement with expected value (of 90.8mV/°C), but some of the parameters are loosely defined

  18. CMS FED Testing Temperature Measurement Errors Temperature stabilisation is good, with random fluctuations of the order 0.02°C. There is some unknown systematic error, that does not exceed 0.44°C. Have statistics of 150x500 voltage points and 150 temperature points per temperature setting. Statistical errors are too small to account for the largest random deviation, probably spurious. We could repeat the whole measurement again using smaller T steps, but probably won’t due to time constraints.

  19. CMS FED Testing Summary Have a complete working single fibre, possible to drive 4 with identical signals using the current Opto-Tx. Possible to obtain a further 2 of the 4 channel prototypes from CERN  complete 12 channels could in principle be driven with identical signals. Dependence of laser operation on temperature is now better understood, and fine temperature control is possible. We feel confident that a system such as the one we have will allow sufficient temperature stability for the fed testing needs. Work is in progress to produce an application specific version of the SEQSI simpler operation longer RAM pipeline clean/synchronous stop from VME possible stepping through

  20. CMS FED Testing Future Work Have 1 (untested) Opto-Rx emulator to drive the analogue stage of the FED directly over copper (I.e. eliminating the optical link) Verify DAC Linearity: Summer student(?) More thought into a test vectors and their comparison with the FED output

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