RE: [SI-LIST] : Ground gap problem

Fox, Michael J (michael.j.fox@intel.com)
Mon, 3 May 1999 18:04:49 -0700

I may be confused about your question:
Are you asking whether the decoupling capacitor should be in series between
the power and ground plane as opposed to in parallel across the
directly-connected pin and plane?
If it's what you're asking, the series option would be very bad indeed. No
DC current will flow through the capacitor and your chip won't be powered.

The second method is how I've always heard it.

-----Original Message-----
From: Rajkumar C [mailto:craj@india.ti.com]
Sent: Monday, April 26, 1999 12:11 PM
To: si-list@silab.eng.sun.com
Subject: RE: [SI-LIST] : Ground gap problem

Hi guys,

I have a very basic question.
Generally, there is a guideline that every
IC's used in the PCB should have a decoupling
capacitor near the power and ground pins.
Here is my question:
In the PCB, I have a separate power plane and
ground plane. For all the IC's I am using the Decoupling
capacitors.

* connect the power and ground pins to the Decoupling
capacitors first and then connect the capacitors to Planes
(or)
* Connect the Power and ground pin to the plane directly and
have decoupling capacitors connected to power and ground plane
and also placed near the IC's power supply pin.

In the above two methods which is best and why?

Expecting your answers.

Thanks and regards,
Rajkumar.

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