[SI-LIST] Re: What does it means my Power Plane Impedance
- From: "mahesh@xxxxxxxxxxxxxxx" <mahesh@xxxxxxxxxxxxxxx>
- To: Shahbaz Assad <shahbaz_assad@xxxxxxxxxxx>,<si-list@xxxxxxxxxxxxx>
- Date: Wed, 08 Sep 2010 14:19:41 +0530
Replies embedded below
At 01:56 PM 9/8/2010, Shahbaz Assad wrote:
>Hi Experts,
>
>What does it means by power plane impedance while doing Power
>Integrity analysis.
>
>The power plane impedance is kept at mili ohms for a wide range of
>frequencies for better PI.
>
>Kindly guide me
>
>1. what does it means by power plane impedance? The impedance seen
>by the IC Chip between the Vcc adn GND planes, to put it in a simple
>(but not exactly true) way.
>2. what should be its nominal value? As low as possible, ideally 0 ohms
>3. For better PI, should its value be as small as possible like
>2mOhms? Yes. Theoretically consider wires connected to the vcc and
>gnd pins of a chip which have 0 inductance and 0 resistance. That
>would be an ideal case with 0 power plane impedance. But
>unfortunately this never happens in real life.
>4. if yes? what is the reason. One issue in power plane is
>resonance. All conductors comprise R,L,c. With any RLC comes
>resonance frequencies. The impedance of circuits changes
>dramatically at resonance frequencies. For example an ideal C and L
>in series has zero impedance at resonance frequency and an ideal C
>and L in parallel has infinite impedance at resonance
>frequency. Effectively, at resonance frequency the power plane
>presents a high impedance to the chip so current will not flow in
>easily as needed at that frequency.
>
>
>Thanks In advance. I am new to SI and PI
>
>
>Thanks,
>Shahbaz Assad
>
>System design Engineer - WhizzSystems, Inc.
>
>_____________________________________
>Skypes ID: sassad85 |
>sassad@xxxxxxxxxxxxxxxx
>
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