1. IEEE10/NSS R. Kass N21-4 1 A. Adair, W. Fernando, K.K. Gan, H.P. Kagan, R.D. Kass, H. Merritt, J. Moore, A. Nagarkar, S. Smith, M. Strang The Ohio State University P. Buchholz, A. Wiese, M. Ziolkowski Universität Siegen OUTLINE Introduction Result on PIN Receiver/Decoder Chip Result on VCSEL Driver Chip Summary

2. IEEE10/NSS R. Kass Proposal to add one more layer to the current pixel detector: Insertable B-Layer or IBL Installation ~ 2015-6 Optical readout will use VCSEL/PIN array Propose to use an updated version of current driver ( VDC ) & receiver/decoder ( DORIC ) chips Upgrades include redundancy & individual VCSEL current control Valuable experience for development of SLHC system Experience gained from the development/testing of such new chips would help the development of on-detector array-based opto-links for SLHC Will discuss results from 1 st prototype chip (130 nm) submitted 2/2010, received 6/2010, beam test 8/2010 N21-4 2 ~1.85m

3. IEEE10/NSS R. Kass Chip Content Decoder (40/80/160/320 Mb/s, spare) Decoder (40Mb/s) Design Photo CML Driver with pre-emphasis VCSEL Driver with pre-emphasis VCSEL Driver VCSEL Driver (spare) 1.5 mm VCSEL: Vertical Cavity Surface Emitting Laser diode VDC: VCSEL Driver Circuit PIN: PiN diode DORIC: Digital Optical Receiver Integrated Circuit The DORIC decodes bi-phase mark encoded clock & commands N21-4 3

4. IEEE10/NSS R. Kass PIN Receiver/Decoder PIN Prototype chip only. N21-4 4

5. IEEE10/NSS R. Kass Command Decoder Interface Courtesy of FE-I4 of IBL Prototype: majority voting, 3 command decoders Production: majority voting, up to 11 command decoders In prototype chip only N21-4 5

6. IEEE10/NSS R. Kass Test card chip Decoder Test Card PIN opto-pack ULM 5 Gb/s N21-4 6

7. IEEE10/NSS R. Kass Recovered Clock/Data 320 Mb/s Decoded clock Decoded data Decoder recovers clock & data from bi-phase mark input stream N21-4 7

8. IEEE10/NSS R. Kass PIN Receiver/Decoder All channels work at 40 Mb/s Multi Speed version works at 40, 80, 160, & 320 Mb/s 160 & 320 Mb/s need external bias tuning for proper operation Steering signal to the spare channel works Peak-to-peak clock jitter: 40 Mb/s: 1420 ps ( multi speed ) 80 Mb/s: 750 ps 160 Mb/s: 193 ps 320 Mb/s: 103 ps Threshold for no bit errors: 40 Mb/s: Multi speed:40  A Ch 1:19  A Ch 2:22  A Ch 3:20  A 80 Mb/s: 58  A 160 Mb/s:74  A 320 Mb/s:110  A Measured Jitter & Threshold N21-4 8

9. IEEE10/NSS R. Kass VCSEL Driver Section Channel Select (3:0) Command Write Write Enable (3:0) DAC Bits (7:0) input added for prototype chip only. Set DAC VCSEL N21-4 9

10. IEEE10/NSS VDC Test Setup Light from the 4 VCSELs R. Kass Opto-chip Finisar 5 Gb/s VCSEL array Fiber aligned over VDC/VCSEL 2 N21-4 10

11. IEEE10/NSS VDC Results Power-on reset circuit In the present pixel detector an open control line disables 6 opto-links Prototype chip has a power-on reset circuit chips will power up with several mA of VCSEL current Test port can steer signal received to spare VDC/VCSEL can set DAC to control individual VCSEL currents All 4 channels run error free at 5 Gb/s includes the spare with signal routed from the other inputs R. Kass N21-4 11

12. IEEE10/NSS VCSEL Driver with Pre-Emphasis Pre-emphasis working with tunable width and height R. Kass Main amplitude Pre-emphasis 160 Mb/s N21-4 12

13. IEEE10/NSS Eye Diagrams @ 4.8 Gb/s R. Kass No pre-emphasis Rise/fall times: ~60-90 ps Measured with 4.5 GHz optical probe Bit error rate < 5x10 -13 VDC 3 Spare VDC: rerouted from VDC 2 N21-4 13

14. IEEE10/NSS Irradiation Results 2 chips were packaged for irradiation with 24 GeV/c protons at CERN in August 2010 Each chip contains 4 channels of drivers and receivers Total dose: 1.6 x 10 15 protons/cm 2 All tests are electrical to avoid complications from degradation of optical components Long cables limited testing to low speed Observe little degradation of the devices Evaluation of full performance await the return of devices to OSU from CERN R. Kass N21-4 14

15. IEEE10/NSS R. Kass VDC Irradiation Results VDC driving 25 Ω with constant control current (CC) Previous VDC prototypes (130 nm) irradiated in 2008 Drive current decreases with radiation for constant CC driver circuit fabricated with thick oxide process PMOS and NMOS have different threshold voltage shifts Use only PMOS in the current mirror in 2010 prototype See improvement in the 2010 version N21-4 15 2010 2008

16. IEEE10/NSS R. Kass Single Event Upset Rate SEU hardend latches or DAC could be upset by traversing charged particles 126 latches per 4-channel chip SEU tracked by monitoring the amplitude of the VDC drive current 13 instances (errors) of a channel steered to a wrong channel in 71 hours for chip #1 Similar upset rate in chip #2 Estimate SEU rate: σ = 1x10 -16 cm 2 particle flux ~3x10 9 cm -2 /year @ opto-link location SEU rate ~3x10 -7 /year/link N21-4 16

17. IEEE10/NSS R. Kass Summary Prototyped opto-chip for 2 nd generation ATLAS pixel opto-links Incorporated experience from current opto-links by adding: redundancy to bypass broken PIN or VCSEL channel individual VCSEL current control power-on reset to set VCSEL current to several mA upon power up Results of tests: VCSEL driver can operate up to ~ 5 Gb/s with BER < 5x10 -13 PIN receiver/decoder works even at low threshold Only small decrease in VDC output current after irradiation Very low SEU rate in latches/DAC All added functionalities work! All results are preliminary N21-4 17