[SI-LIST] Re: Decoupling at 800Mhz
- From: Stefan Ludwig <ludwig@xxxxxxxxxxxxxxxxx>
- To: Subramanian R <subramanian1683@xxxxxxxxx>
- Date: Sat, 24 May 2008 11:35:24 +0200
Hi Mani,
if the processor runs at 800MHz, it doesn't mean that the decoupling
requirement for the PCB will be at 800MHz. Typically, the spikes at
800MHz will be taken care of by on-die capacitance.
As was said by others on this thread and you below, the mounting
inductance of the package on the board and the inductive path through
the package to the die will limit what you can do on the board. 1uF in
0402s as close to the power/gnd pins of the package, mounted with
vias-in-pad or vias to the side of the pads will be the best you can do
- in addition to having close spacing between pwr & gnd planes.
Typically, what you'll see on the board is in the range of 50-250MHz,
depending on how well the package is designed.
I hope this helps.
Cheers,
Stefan
Subramanian R wrote:
> Hi All,
> We are planning to use a processor running at 800 MHz.
> I was just reading up on the decoupling methods.
>
> The Processor PCB guidelines recommend using 1uF 0402 pack for high
> frequency decoupling. But at 800 MHz, will not the cap/package inductance
> dominate.
>
> The guideline doesn't say anything about plane decoupling also.
>
> Am I missing something? What are the best approaches for decoupling?
>
> Any suggestions will be very useful.
>
> Thank you in advance,
>
> Regards
> Mani
>
--
Ludwig Systems Engineering Consulting - Design - Implementation
WWW: www.ludwigsystems.com System Architectures - FPGAs - PCBs
Ph/Fx: +41-43-355-58-73/74 Hardware - Firmware - Software
------------------------------------------------------------------
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 technical documents are available at:
http://www.si-list.net
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
Other related posts:
