[SI-LIST] Re: decoupling
- From: Chris Cheng <chris.cheng@xxxxxxxxxxxx>
- To: "'si-list@xxxxxxxxxxxxx'" <si-list@xxxxxxxxxxxxx>
- Date: Thu, 12 Jul 2001 12:36:09 -0700
believe me i have the best &^%$* package. you are confusing signal traces
that have pf of loading and 1nh of inductance with core that has uf's of
loading and ph's of inductance. orders of magnitude difference in resonance.
i have done a few ghz processes with >100W power packaging with the best
flip chip substrate. you can put a million low impedance cap solder right
at the pin of the package and it won't make a &^%$* difference to the
core noise >100MHz. what ghz processes have you done ?
-----Original Message-----
From: Ed Priest [mailto:Ed_Priest@xxxxxxxxxxxxxx]
Sent: Thursday, July 12, 2001 10:09 AM
To: 'si-list@xxxxxxxxxxxxx'
Subject: [SI-LIST] Re: decoupling
You can pass out a +ghz signal single endedly and if you think you can't get
> 100Mhz noise out of a package you are using some really &^%$* packages or
are using die that don't have >100Mhz switching activity. In a package with
coupled planes - the power planes look like transmission lines with
distributed poles and zeros. Good flip chip packages have very low impedance
between PCB and the die. I guarantee you can get high frequency noise down
to the PCB - I've help troubleshoot a lot of boards for people who thought
they couldn't. If you have a bunch of chips on a board with 400Mhz
switching, spending time lowering the impedance of your power distribution
at 400Mhz is time well spent.
Ed
-----Original Message-----
From: Chris Cheng [mailto:chris.cheng@xxxxxxxxxxxx]
Sent: Wednesday, July 11, 2001 6:13 PM
To: 'si-list@xxxxxxxxxxxxx'
Subject: [SI-LIST] Re: decoupling
ghz+ signals come out as differential signals. and 400mhz+ signals
come out as transmission lines. most packages, coupled with on
die capacitance resonant around 100mhz or below.
>For you comment that 400Mhz can not propagate through the package ( good
packages can propagate higher frequencies >>than that) - how to you think
the Ghz + signals get out. The noise that comes out is a voltage divider
between the >reactance on the die/package and the power distribution
impedance on the board - another way to see why you want the >impedance on
the board to be small.
>
>Ed
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