CMS FED Testing Update M. Noy Imperial College Silicon Group

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

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

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

CMS FED Testing DAC scope UTP V out Opto-Tx DAC Evaluation Board Line driver Opto-Rx

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.

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

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).

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

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

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)

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

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

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)*( ) = *1021=671mV

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. 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

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) Temperature: have observed significant temperature variation of the signal =>Define the laser temperature stability requirements for testing Verify DAC Linearity: Summer student More thought into a test vectors and their comparison with the FED output CMS FED Testing