The message was cutted somehow; resending:
Agree that 300MHz is a resonance of a cavity due to power and ground planes.Â
The 30MHz is a resonance of chip' die capacitance and VRM inductance.
Regards,Â
Iliya Zamek Â
On Wednesday, December 25, 2019, 11:51:49 AM PST, Iliya Zamek
<dmarc-noreply@xxxxxxxxxxxxx> wrote:
s.Â
The 30MHz is a resonance of chip' die capacitance and VRM inductance.
Regards,Â
Iliya Zamek Â
  On Wednesday, December 25, 2019, 11:13:27 AM PST, Lee Ritchey
<leeritchey@xxxxxxxxxxxxx> wrote:Â
The resonance at 300 MHz is due to the fact that the plane pair is a quarter
wavelength long at its longest dimension.
The 30 MHz resonance depends on what your VRM module looks like.
Lee Ritchey
Speeding Edge
P.O. Box 817
Bodega Bay, CA
94923
408-781-0253
I took the energy needed to be mad
And wrote some blues
Count Basie
Worry is like a rocking chair,
It keeps you busy, but doesn't get you anywhere.
Ross Ritchey
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx <si-list-bounce@xxxxxxxxxxxxx> On Behalf
Of Akunuru Venkata Naga Kalyan Ram
Sent: Tuesday, December 24, 2019 6:15 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Fwd: Help: Resonance frequencies for Power Plane
Hello PI/SI experts,
Happy Holidays. I have a question, I have designed a simple 6" x 6" board
with 4 layers. Power Layer is on 2nd layer and ground layer is on 3rd layer.
Dielectric is FR-4 (8 mil thick).
I have defined a simple IC as VRM which is at the edge of the board and a
sink is placed on the centre of board.
[image: board.PNG]
I have performed a PDN Analysis on this and without any Decaps placed on the
board, the impedance plot has 2 resonance points at 30 MHz and 300 MHz.
I want to understand how this phenomenon is happening and what is causing
this resonance at 2 frequencies. There might be plane capacitance and
inductance acting on it. Is there any way to calculate this by hand or any
thumb rules present that might help me to understand this.
[image: Capture.PNG]
Any help would be appreciated. Thank you and Merry Christmas to everyone.
Warm Regards:
Kalyan Ram
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