[SI-LIST] Re: SSN Vs Load cap
- From: "joshuakh@gmail" <joshuakh@xxxxxxxxx>
- To: erdinih@xxxxxxxxx
- Date: Fri, 2 Feb 2007 10:08:56 -0500
Canes,
I'd like to know what your exact loading condition will be.
Is it a simple capacitor or with 50 Ohm parallel etc?
The reason I am asking you about this is that you might miss the time window
you want to consider in your thought experiment.
I hope this will help.
Joshua Kihong Kim
On 2/2/07, Ihsan Erdin <erdinih@xxxxxxxxx> wrote:
>
> Canes,
>
> Sabayachi's explanation is plain and accurate. i=Cdv/dt is a lumped
> approximation to Maxwell-ampere eq.; so is v=Ldi/dt to
> Maxwell-Faraday. As such, both have physical connotations. Your
> di/dt=Cdv2/dt2 is mathematically correct but doesn't have any useful
> physical connotations.
>
> Regards
>
> Ihsan
>
> On 2/2/07, Canes Venatici <starsilic@xxxxxxxxx> wrote:
> > Upto the maximum current driving capability of driver, the increase in
> load capacitance causes
> > the current rate to increase and noise increases, so SSO index should
> reduce.
> > Once its reached the maximum drive capability at a particular load cap,
> the increase of cap
> > causes the rate of voltage to fall, as per the max. current spec. But
> since the current remains same (as the driver
> > cant supply more than that), I expect SSO index to be unchanged.
> > Equations :
> > i = c. dv/dt
> > di/dt = c.(d2v/dt2) ....(its d square v by dt square)
> > sso noise = L.di/dt = L.c.(d2v/dt2).
> >
> > Please clarify, if I'm missing anything.
> >
> > Regards
> > Canes
> >
> > ----- Original Message ----
> > From: Sabyasachi Mohapatra <sabbu1981@xxxxxxxxxxx>
> > To: si-list@xxxxxxxxxxxxx
> > Sent: Thursday, February 1, 2007 6:13:12 PM
> > Subject: [SI-LIST] Re: SSN Vs Load cap
> >
> > It is pretty simple.
> > as u increase the load cap with same drive strength of driver,
> > rise or fall slew will degrade.
> > As the buffers will be switching slower now, dI/dt will be less,
> > rate of change of current though package inductor will be less.
> > So less SSO noise.
> >
> > --- In si-list@xxxxxxxxxxxxxxx, Canes Venatici <starsilic@...> wrote:
> > >
> > > Hi all,
> > > I couldn't understand why if load capacitance is increased, SSN is
> > reduced (as the recommendation is increased SSO index, more signal
> > pads can be accommodated by power pads).
> > > As di/dt is directly proportional to load cap, increasing the load
> > causes more drop in parasitic inductance and SSN should increase.
> > > Could anyone clarify.
> > > Thanks,
> > > Canes
> > >
> > >
> > >
> > >
> > >
> > >
> > >
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