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Politics : Formerly About Advanced Micro Devices -- Ignore unavailable to you. Want to Upgrade?

To: Maxwell who wrote (35181)	7/29/1998 10:14:00 AM
From: Time Traveler	Read Replies (1) \| Respond to of 1572772

Maxwell, >>"The impedance of a capacitor is 1/(jwC) where w=2Pifrequency and C=capacitance."<< That is correct. I never deny that fact, but this impedance is very much useless in our discussions. A better way to write 1 / j w C is 1 / s C where s = j w. The impedance relationship is great to do filters including control compensation. Please consult with our resident system engineer, Petz. >>"At high frequency the impedance between the metal lines act like a "short" and starts to crosstalk."<< OK, this should better be not the case in K6! >>"At low frequency low K is unimportant."<< How low of frequency are you referring to? We are talking about 10MHz and up, right? You are right. At frequency way below 10MHz, power dissipation due to the leakage current of all the FETs combined dominates. Do you know what frequency (or range of) that would be? The maximum speed besides the gate-chain is limited by the R and C of a simple inverter stage. R is dominated by the channel on-resistance, not the trace resistance which you can replace Al with Cu. C is lowered by reducing the K, dielectric constant, or the area, by shrinking the feature size. Power dissipation is proportional to C V^2 f, where V = DC supply voltage and f = operating frequency. As you can see, C plays a very important role in both speed and power dissipation at the frequency we are interested. And this is why most of the industry think lower K is more important than copper stuff. Time Traveler