Lookup NU author(s): Professor David Kinniment,
Dr Alex Bystrov,
Professor Alex Yakovlev
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Synchronizer circuits are usually characterized by their rate of failure in transmitting data between two independently timed regions. The mean time between failures (MTBF) is assumed to be MTBF = et/τ/Tw · f1 · f2, where f1, and f2 are the clock frequencies on either side of the interface, τ and Tw are constants. Here, t is the time allowed for the synchronizer circuit to reach a stable value after clocking. Previous experimental work has shown that the slope of the histogram relating the logarithm of failure probability to t is not always constant. We show that these effects, which include an apparent reduction in the value of τ in the early part of the histogram to as much as 60% of the final value, can be explained by extending the existing theory to take account of initial offsets, and we propose a new, more accurate, formula: MTBF= et/τ(b)/[(Ve/Vt-v - (Vs/Vt-v) e-t/τ(a)] · f1 · f2 where Vs, Ve, Vt-v, τa, and τb are circuit constants. Synchronizer performance depends on achieving a high reliability of synchronization together with a short time. We show that commonly used circuits, such as the jamb latch, do not produce the best compromise for very high reliability applications, and that a circuit with a lower value of τ can be designed. In order to confirm that thermal noise does not influence the MTBF against synchronization time relationship, we have devised an experiment to measure noise in an integrated CMOS bistable circuit. We show that the noise exhibits a Gaussian distribution, and is close to the value expected from thermal agitation.
Author(s): Kinniment DJ, Bystrov A, Yakovlev A
Publication type: Article
Publication status: Published
Journal: IEEE Journal of Solid-State Circuits
Print publication date: 01/02/2002
ISSN (print): 0018-9200
ISSN (electronic): 1558-173X
Publisher: IEEE Computer Society
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