[SI-LIST] Re: DC Drop in PDN simulation
- From: matthew leslie <mbleslie@xxxxxxxxx>
- To: mnithink@xxxxxxxxx
- Date: Fri, 30 Aug 2013 08:44:16 -0600
In general, s-parameter models are not reliable below a certain frequency
range. It depends on the extraction tool, but typically that range is
around 1-100MHz. Sometimes the tool refuses to extract below a certain
frequency (I believe HFSS does this). Sometimes the tool will agree to
generate a model for low frequencies, but that model is erroneous. For
example, the tool might simply extrapolate "accurate" data in the 1-10MHz
range down to kHz and DC. Other tools switch the field solver techniques
when transitioning to lower frequencies and as a result end up creating
models with discontinuities in insertion/return loss.
There are some steps you can take to better ensure accuracy at low freq for
s-param model. Make sure you are using a low reference impedance, such as
1-ohm or 0.1ohm. Also, if your solver permits, try forcing a separate DC
solution into s-param model. Unfortunately, this doesn't guarantee accuracy
from DC up to the 1-100MHz range.
S-parameter models that are accurate from DC to multi-GHz (as far as I
know) is a big challenge. If I were you, I might move to creating an RLGC
or other type of lumped element model for more accurate low frequency
representation.
On Fri, Aug 30, 2013 at 8:26 AM, Nithin Kumar <mnithink@xxxxxxxxx> wrote:
> Hello Experts,
> I'm doing PDN simulation using DIE model ( from Redhawk), PCB model and
> Package model (s-parameter)
> During transient analysis I'm seeing huge drop at the bga balls as well as
> die bump.
> I have verified the resistance values of package and PCB ( which are very
> small) and varied DIE R as well. But i'm not able to reduce this huge DC
> offset.
> can anybody through some light on possible reasons for such an offset?
>
> --
> -------------------
> Regards,
> Nithin Kumar
>
>
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--
Matthew B. Leslie
mbleslie@xxxxxxxxx
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