[SI-LIST] : on-chip capacitance & core noise

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From: Sandy Taylor (cmos@rockisland.com)
Date: Thu Jul 20 2000 - 11:05:47 PDT


David Chengson wrote:

> Does anyone have some approximate numbers for
> the amount of on-chip capacitance that has been explicitly
> added to large commercial or non-commercial chips?

...

David

I co-authored a paper at Sun Microsystems which was presented
ISSCC 2000 describing the passive on chip decoupling caps
and the active circuit used to counter multi cycle effects.

Here are the numbers from that paper:

Passive capacitance added: 176 nF
Intrinsic chip capacitance: > 80 nF
On chip regulator capacitance: 134 nF (when deactivated)
regulator capacitance (switching): 1.6uF

This was for a 1.5V 0.15u CMOS device.

The on chip regulator uses actively switched decoupling capacitors to
decrease the AC impedance in a band limited range.
The target band was to cover the region between where the on chip passive
decoupling caps run out of gas and when the package(...) inductance
finally allows the current to change.

Keeping the on chip power supply impedance down in the
single digit mOhms is tough.

I hope this helps you.

Sandy Taylor

(360) 376 3815
CMOS Solutions
Orcas Island WA.

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