--1-- An exploration of synchronization solutions for parallel short-range optical interconnect in mesochronous systems Harald Devos.

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1 --1-- An exploration of synchronization solutions for parallel short-range optical interconnect in mesochronous systems Harald Devos

2 --2-- Introduction Optical links Synchronization Designs and simulations Conclusion

3 --3-- Introduction Bitrate of electrical interconnects limited by the aspect ratio *: * D.A.B. Miller and H.M. Ozaktas use of Optical Interconnects

4 --4-- Introduction long haul short haul

5 --5-- Introduction long haul short haul BW, bitrate also latency important

6 --6-- Introduction long haul short haul BW, bitrate also latency important high density, parallel

7 --7-- Introduction long haul short haul BW, bitrate also latency important high density, parallel mesochronous Synchronization needed

8 --8-- Introduction Optical links Synchronization Designs and simulations Conclusion

9 --9-- Optical links

10 --10-- Optical links latency IN OUT

11 --11-- Optical links eye-diagram

12 --12-- Optical links Jitter: HF, LF (wander) 2J T

13 --13-- Optical links Skew S T S

14 --14-- Optical links

15 --15-- Introduction Optical links Synchronization Designs and simulations Conclusion

16 --16-- Synchronization Synchronization = move data to the local clock domain Determine the phase Adjust the phase

17 --17-- Synchronization Adjusting the phase Clk Data Auxiliary Clk

18 --18-- Synchronization Adjusting the phase Clk Data Auxiliary Clk

19 --19-- Synchronization Adjusting the phase DQDQ Clk Data Auxiliary Clk ?

20 --20-- Synchronization Auxiliary clock: one of n clock phases Clk = C1 C1 C2 C3 C4 C5 T/5 e.g. n = 5

21 --21-- Synchronization Choice of auxiliary clock T/n T/2n T/n

22 --22-- Synchronization Parallel ? T/2-J-S T S T/2n

23 --23-- Introduction Optical links Synchronization Designs and simulations Conclusion

24 --24-- Designs Parallel Serial nn f f fff n.f n n Ref. Determine phase: use of a reference link

25 --25-- Designs AMS 0,6 µm – technology, standard libraries, state-of-the-art Different phase detection: 1. AJTI: ‘artificial jitter injection’ 2. Flip-flop phase detectors

26 --26-- Designs: AJTI Determine phase with AJTI Ref. …0101… 0101

27 --27-- Designs: AJTI Determine phase with AJTI Ref. …0101… 0101 AJTI

28 --28-- Designs: AJTI Determine phase with AJTI Ref. …0101… 0101 0000

29 --29-- Designs: AJTI Disadvantages Reference: not flexible Initialization Extra delay

30 --30-- Designs: FF phase detectors Determine phase with flip-flop phase detector Ref. ck ckQ Suited clock phases

31 --31-- Designs: FF phase detectors Advantages Flexibility reference signal –Data signal –PRBS –Serial word synchronization

32 --32-- Designs: comparison AJTI 2 or more clock phases Extra delay Initialisation problem Ref.=010101… FF phase detectors At least 4 clock phases Minimal delay Initialisation OK Ref.= signal with transitions

33 --33-- Designs Area and Power consumption

34 --34-- Introduction Optical links Synchronization Designs and simulations Conclusion

35 --35-- Conclusion If skew en jitter are sufficiently low, synchronization can be optimized Using an extra link can simplify the circuits Greater uniformity needed to minimize skew

36 --36-- Acknowledgments Joni Dambre, Wim Meeus, Dirk Stroobandt and Jan Van Campenhout

37 --37--

38 --38-- Questions ? ?

39 --39--

40 --40-- Not mentioned Generation clock phases Influence of coding Comparison Synchronization circuits

41 --41-- Designs: flip-flop phase detector

42 --42-- Optical links Properties optical links: Latency Jitter Skew

43 --43-- Optical links Optical link

44 --44-- Optical links Soorten ontvangers: Transimpedantie versterker (TIA) - belangrijk statisch verbruik => verbruik per bit neemt af met stijgende frequentie

45 --45-- Optical links Soorten ontvangers: Geklokte versterker (sense-amplifier) - vooral dynamisch verbruik => verbruik per bit weinig afhankelijk van frequentie - zuiniger dan TIA - na bemonsteren geen ‘skew’ meer - klok nodig

46 --46-- Optical links Klok nodig Meezenden referentiesignaal extra kost extra voordeel Ook nuttig voor niet-geklokte ontvangers ?

47 --47-- Synchronization Mesochronous:

48 --48-- Designs: AJTI Voordelen,benefits profits: - Methode bruikbaar voor willekeurig aantal fasen

49 --49-- Designs: Gemeenschappelijke kenmerken Kost ~ 1/(# parallelle links) Hulpklok volgt fase bij drift Hulpklok: n e 1 e fase bit kwijt ! 1 e n e fase 2 maal zelfde bit!

50 --50-- Introduction Optical links Synchronization Designs and simulations Conclusion