[SI-LIST] Re: RE：How can we get the resonance frequency and Q between
- From: steve weir <weirsi@xxxxxxxxxx>
- To: Luping LIU <liewluping@xxxxxxxxx>
- Date: Tue, 04 Dec 2012 17:16:27 -0800
You are unfortunately in an information vacuum created by your supplier.
They themselves may be in an information vacuum. The more that they tell
you to just do something without providing supporting data, the more you
should be concerned.
I would evaluate the back-side capacitor problem by determining or at
least estimating the inductance in the Z axis interconnects and working
from there.
Steve.
On 12/4/2012 3:10 PM, Luping LIU wrote:
> Hi Michael:
> Yes,use the high ESR decouple capacitor was written in the application
> notes, we are checking with the vendor now.
> but, if it is explained by some measurement will help us to get more
> information,Vendors are always smarter than me .
>
> Besides the high ESR problem,the application notes also suggest to use
> 1uF 0402 capacitor below the BGA for most of the core power pins,
> though it may be a traditional big-V design style, why not us 100nF or
> mixed number of two caps?
> It will extend the impedance curve cross the target at higher
> frequency,is it because they need larger capacitance for high dynamic
> current but worried about he higher Q of the anti-resonnance so they
> suggest to use high ESR caps? That's my personal guess,may be wrong
> drection,thank you for your helps:)
>
> LIU Luping
>
> ·¢¼þÈË: Michael Greim <mgreim001@xxxxxxxxx <mailto:mgreim001@xxxxxxxxx>>
> Ö÷Ìâ: Re: [SI-LIST] Re: RE£ºHow can we get the resonance frequency and
> Q between
> ÊÕ¼þÈË: weirsi@xxxxxxxxxx <mailto:weirsi@xxxxxxxxxx>
> ³ËÍ: "luping liu" <liewluping@xxxxxxxxxxxx
> <mailto:liewluping@xxxxxxxxxxxx>>, si-list@xxxxxxxxxxxxx
> <mailto:si-list@xxxxxxxxxxxxx>
> ÈÕÆÚ: 2012Äê12ÔÂ3ÈÕ,ÖÜÒ»,ÏÂÎç9:12
>
> LIU,
> OK, I'll ask. Did you ever ask why the reference
> design is this way? Is it consistent with their own
> design guidelines? We are all doing alot of speculating
> as to why these caps are there and it simply may have
> been a board design oops, reference design or not.
> Like Steve said, that is a classic, intentionally designed
> in (whether meant or not) oops. You can also ask
> your vendor for information about the package. Worst
> thing they can say is "No", and if they ask why you have
> a very good answer.
> -Michael.
>
> We will either find a way or make one - Hannibal
>
> In the middle of every difficulty lies opportunity - Al Einstein
> If you think you can do something or you think
> you can't, in both cases you are probably right - H Ford
> If you're not getting the results you want with the
> current approach, move on and try something else. - A. Fleischmann
>
--
Steve Weir
IPBLOX, LLC
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