[SI-LIST] Re: Lout of VRM
- From: "sogo_hsu" <sghsu55@xxxxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Thu, 15 Aug 2002 15:29:19 -0000
Istvan,
Thank you for your response. I know the effect of violation in
target impedance. However, actually, it is hard to find a proper
inductor to match the specification of today's PDS. In contrast, If I
used a shorted inductor instead of 1 uH, will VRM and/or PDS work
properly?
Best regards,
--- In si-list@xxxx, "istvan novak" <istvan.novak@xxxx> wrote:
>
> Sogo,
>
> If you dont change anything else, only the inductor will be of
> ten times lower value, the ripple current through the inductor
> will be ten times higher. If otherwise the 1uH inductor was
> properly designed for the application, the ten times higher
> ripple current will most probably drive its core to saturation
> or at least the losses will increase significantly. If you see
> a 1kHz peak in the impedance profile with 1uH output
> inductor, the probable cause is a suboptimal control loop.
>
> regards
>
> Istvan Novak
> SUN Microsystems
>
> ----- Original Message -----
> From: "sogo_hsu" <sghsu55@xxxx>
> To: <si-list@xxxx>
> Sent: Wednesday, August 14, 2002 10:35 AM
> Subject: [SI-LIST] Lout of VRM
>
>
> >
> > Hi SI Gurus,
> > Firstly, I have got lots of help from this forum; I have to say
> > thank you to all give me advises in advance. Recently, I had done
> > several simulation works regarding PDS design. We computed the
> > impedance of PDS including the model of VRM. Roughly said, the
VRM is
> > almost three-phase type and with 1uH inductor type we adopted.
That
> > is said, the equivalent output inductance is 0.333uH. The
simulation
> > result indicated the impedance of PDS has a peak violates the
> > specification of target impedance at about 1 kHz. We proposed
> > dwindling the inductor from 1 uH to about 100 nH to match the
> > specification of target impedance. However, it is hard to find
the
> > proper component to match the requirement. I have some questions
> > regarding the simulation work.
> > (1) What=A1=A6s the role of output inductor in VRM? It seems
lower
> > output inductor of VRM makes up lower impedance of PDS. So,
what=A1=A6s
> > the aftereffect if a low output inductor, even we shorten the
output
> > inductor, was adopted?
> > (2) If we ignore the violation at about 1KHz due to the
> > =A1=A5high=A1=A6 inductor, what=A1=A6s happen in PDS design?
> > Thank you for your helps in advance.
> > Best regards,
> > Sogo Hsu
> >
> >
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