[SI-LIST] Re: Lout of VRM
- From: "istvan novak" <istvan.novak@xxxxxxxxxxxxxxxx>
- To: <sghsu55@xxxxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Wed, 14 Aug 2002 21:22:15 -0400
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@xxxxxxxxxxxx>
To: <si-list@xxxxxxxxxxxxx>
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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