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Article #706Re: 3.3V v/s 5V
From: Shih-Lien Lu
Date: Sat, 25 May 1991 20:42
Date: Sat, 25 May 1991 20:42
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1956 bytes
>In article <1956@ole.UUCP> ssave@ole.UUCP (Shailendra Save) writes: >> >> In this week's Electronic Engineering Times (May 20th issue) >> there is an article about AT&T developing a 3.3V cell library. >> On pp 16, (bottom 2nd column) they claim: >> >> The basic 2 input NAND-gate power rating is 6.1uW/MHz at 5V >> dropping to 1.1uW/MHz at 3.3V >> >> I am missing something here. If it is a CV^2 relationship, >> it should be approx. 2.5 and not 1.1 >> >> Shailendra > >The way these things work is that the charging current available is a >function of the difference between the power supply voltage and the >enhacement threshold voltage of the fets. As you reduce the power >supply voltage, the circuit gets slower (and ultimately stops working) >at the same time the uW/Mhz get smaller, ultimately going to zero when >the fets no longer are turned on at all. > >Arnold Frisch >Tektronix Laboratories Are you saying that because Id is smaller, the integral of V(t)Id(t) dt is smaller? How can one work out the integral? I do not really know the extact AT&T technology. As Shailendra pointed out that the dynamic power dissipation is a CV^2 relationship. Is it possible that the C used in the equation is smaller by a factor of ~2. As I recall the real (somewhat old) "metal-oxide" gate (instead of the modern polysilicon gate) process has a smaller gate capacitances. Is AT&T's process a C"M"OS process? Just curious. Shih-Lien
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arc1-ca.pugleaf.net!utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!elroy.jpl.nasa.gov!ucla-cs!maui.cs.ucla.edu!slluReferences:
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Path: arc1-ca.pugleaf.net!utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!elroy.jpl.nasa.gov!ucla-cs!maui.cs.ucla.edu!sllu From: sllu@maui.cs.ucla.edu (Shih-Lien Lu) Newsgroups: comp.lsi.cad Subject: Re: 3.3V v/s 5V Keywords: Vdd. 3.3v Message-ID: <1991May25.204213.614@cs.ucla.edu> Date: 25 May 91 20:42:13 GMT References: <1956@ole.UUCP> <9577@sail.LABS.TEK.COM> Sender: Shih-Lien Lu Organization: UCLA Computer Science Department Lines: 35 Nntp-Posting-Host: maui.cs.ucla.edu