FreeLists / si-list / [SI-LIST] Re: Decoupling capacitors for BGA

["Mark Alexander" <mark.alexander@xxxxxxxxxx>]

Kishore, Subbu,

I'll note that XAPP623 is getting a bit out-of-date.  For more
up-to-date information on the latest techniques, check out the PDS
section of the Virtex-4 User Guide.  Though it's not as generic as
XAPP623 (it applies specifically to the Virtex-4 device family), the
basic principles it covers apply fairly well to high-speed digital
devices and PCBs of 2006.

I'm finishing up revisions/updates for both of these documents; will
make a post to SI-List when the new versions are published.

-mark



-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Kishore Bachu
Sent: Friday, May 12, 2006 3:48 AM
To: subramanian1683@xxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Decoupling capacitors for BGA

Classification: UNCLASSIFIED

Hi Subramanian,

For your reference, you can find the following article in Xilinx
website.
"Power Distribution System (PDS) Design: Using Bypass/Decoupling
Capacitors"
Xapp623.pdf

Regards,
Kishore.

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Subramanian R
Sent: Friday, May 12, 2006 2:32 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Decoupling capacitors for BGA

Hello All,
We are using a 0.5mm Pitch 457-Pin BGA Processor. It is running at a
maximum of 532MHz.
It has 60 Power pins (Core & I/O)

How do i place the Decoupling capacitors?

Now we have placed all decaps (0402 pack) around the BGA (like an
island) and connected it to the VCC plane. Should i need to route it to
the individual pins itself?

The BGA does not have much space between the Balls. So not more than 4-5
caps can be placed right over the BGA on the other side.

The other thing i can go for is Inter-plane capacitance. But for that
VCC-GND dielectric should be around 2-3mils, i understand. That doesn't
look possible with our PCB thickness requirements. It is a 6-layer PCB

Thanks for any suggestions.

Regards
Subbu

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