[SI-LIST] Resonance Frequency
- From: Wael El Essawy <essawy@xxxxxxxxxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Fri, 23 May 2003 20:17:48 -0400
Larry,
in a previous email you said:
For the last 15 years, the chip/package resonant frequency has been somewhat
under 100 MHz. I worked on a product in 1988 where it was about 80 MHz. The
inductance was about 1 nH, so by my favorite formula, f0 = 1/{2pi*sqrt(LC)},
the capacitance in the chip must have been about 4 nF. Since then, the
capacitance keeps going up and the inductance keeps going down, leaving the
product almost constant. For the product analyzed in the paper, the
capacitance is about 100X what it was in 1988. We tried very hard to reduce
the inductance, but it is not 1/100th of a nH. I guess we have some more
workto do.. That is why the resonant frequency was just 35 MHz. Is this
generally true for high performance microprocessors? In other words can I
assume that chip/package resonance frequency has changed from a fraction of
amicroprocessor cycle to tens of cycles. Can I assume that in future
microprocessors resonance will occur at repeated high current swings over
hundreds of cycles period only?
Thanks
Wael El Essawy
Ph.D. student
ECE Dept.
University of rochester
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