[SI-LIST] Re: S-parameter of dcap
- From: steve weir <weirsi@xxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Tue, 17 Jan 2012 08:01:43 -0800
It all depends on what level of accuracy that you want / need, and what
tools you are using. There are cap manufacturers who supply S parameter
models. Depending on the tool you are using, S parameters may or may
not be what you want. One tool from a major vendor will only deal with
a single L-R-C model.
Modeling a PDN without considering inductance saves a lot of time. It
eliminates the need for bypass capacitors altogether. I highly
recommend it for designs with di/dt's below 1A/s.
Steve.
On 1/17/2012 6:59 AM, Rohit MISHRA wrote:
> Friends,
> I am stuck in a problem so thought it would be better to take assistance from
> all you experts there :)
>
> Actually we need to extract s-sparameter of PDN network of one USB board.
> Board database(.brd) which we have got has all dcaps included and If I check
> capacitance model in database, it has just capacitance value but has no ESR&
> ESL mentioned.
>
> I have tried to find s-parameter of these MLCC dcaps so that I can add them
> in PDN extraction but my bad luck :( all I have got is SRF& ESR.
>
> Now my question is :
>
>
> 1) Do we really need to have s-parameter of dcap for accurate PDN
> extraction ?
>
> 2) If I use dcap spice model instead, do we really need to have ESL in
> that model. Can't we use just ESR& C in spice model ?
> My argument is that ESL of dcap which is mentioned in datasheet or one which
> we can calculate from SRF& capacitance is basically intrinsic/self
> inductance of capacitance lead which in MLCC case will always be much lower
> than mounting& spreading inductance So we shouldn't worry much about ESL of
> dcap while extracting PDN network.
>
> Do you see any problem in this argument ?
>
> Rgds,
> Rohit
>
>
>
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--
Steve Weir
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