Clock Driver Design for Low-Power High-Speed 90-nm CMOS Register Array

Tadayoshi ENOMOTO  Suguru NAGAYAMA  Hiroaki SHIKANO  Yousuke HAGIWARA  

IEICE TRANSACTIONS on Electronics   Vol.E91-C   No.4   pp.553-561
Publication Date: 2008/04/01
Online ISSN: 1745-1353
DOI: 10.1093/ietele/e91-c.4.553
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Advanced Technologies in Digital LSIs and Memories)
power dissipation,  CMOS,  clock,  register,  

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The delay time (tdT), power dissipation (PT) and circuit volume of a CMOS register array were minimized. Seven test circuits, each of which had a register array and a single clock tree that generated a pair of complement clock pulses, and a conventional register were fabricated using 90-nm CMOS technology. The register array was constructed with M delay flip-flops (FFs) and the clock tree, which consisted of 2 driver stages. Each driver stage had m inverters, each of which drove M/m FFs where M was fixed at 40 and m varied from 1 to 40. The minimum values of tdT and PT were 0.25 ns and 17.88 µW, respectively, and were both obtained when m was 10. These values were 71.4% and 70.4% of tdT and PT for the conventional register, for which m is 40, respectively. The number of inverters in the clock tree when m was 10 was 21 which was only 25.9% that for the conventional register. The measured results agreed well with SPICE-simulated results. Furthermore, for values of M from 20 to 320, both the minimum tdT and the minimum PT were obtained when m was approximately 1.5 times the square root of M.