[SI-LIST] Re: Decoupling capacitor and oscillations

From: Bi Han <mike_bihan@xxxxxxxxxxxx>
To: nvasrikanth@xxxxxxxxxxx, List` Si <si-list@xxxxxxxxxxxxx>
Date: Tue, 23 Sep 2003 08:45:38 +0800 (CST)

Dear nvasrikanth:
If you add a about 5ohm resistor serialized with the decoupling capacitor, you
will not see the oscillation normally. Actually, 2-3 ohm will be enough to
damping that oscilation between Bonding wire and decoupling Caps. But your
on-chip decoupling caps will have ESR anyway, so do not have to worry much
about that.

My comments was based on simulation instead of silicon data, you need senior
folks' confirmation to make sure.

BH
nvasrikanth <nvasrikanth@xxxxxxxxxxx> wrote:
Hi,
I am new to this group.

I am simulating a o/p buffer with package parasitics(RLC) to estimate
the switching noise and settling. I found so many oscillations at
15GHz freq. (On chip)Decoupling capacitor is also included in
simulations between vdd and gnd.
I heard that oscillations can occur due to the failure of RLC model at
high frequencies.(skin effect and radiation losses not modelled)

To find the freq of oscillations i did some ac simulations (with the
output buffer as current pulse) with and without decoupling cap .
In the 1st case I saw resonance at 1GHz and 15GHz frequencies.
In the 2nd case I saw resonance at 15GHz freq.

The 1GHz freq is because of decap(1/sqrt(LC)).(may be providing
seperate LC path).

My concern here is whether these kind of oscillations really
occur in actual ICs or not if a decoupling cap is introduced.
If so how to overcome those.

Hope to get some clear help.

Thanks in advance
Srikanth.

------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field

List archives are viewable at:
//www.freelists.org/archives/si-list
or at our remote archives:
http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu

---------------------------------
Do You Yahoo!?
ÆôÓÃµçÓÊÕÊºÅ£¬Áì»áÑÅ»¢Í¨[ÉíÁÙÆä¾³ÁÄµçÓ°]µÄ¶¯¸Ð÷ÈÁ¦£¬»¹ÓÐÍøÂçÉãÏñÍ·+ÑÅ»¢Í¨ÊÕÒô»úµÈÄãÀ´ÄÃ

------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field

References:
- [SI-LIST] Decoupling capacitor and oscillations
  - From: nvasrikanth

[SI-LIST] Re: Decoupling capacitor and oscillations

Other related posts: