FreeLists / si-list / [SI-LIST] Re: Ground bounce (was VOH datasheet question)

[dav0 <david.lieby@xxxxxxxxxxx>]

On top of everything else, a lot of larger packages have on-chip
decoupling capacitors.  These provide a fixed amount of charge to
dump into the system.  Adding more capacitance to the load will
cause a little more SSO.

Regards,
David Lieby

Andrew Ingraham wrote:
>>Is the turn-on time for a driver slow rather than instantaneous?
> 
> 
> Yes.  Drivers don't turn on instantaneously.  It's a combination of on-die
> and package effects.  If you measure turn-on time or slew rate with a
> resistive load, you don't get zero or infinity.
> 
> Increasing the load capacitance increases the area of the current pulse;
> that's all you can say for sure.  Some of it is by lengthening the pulse's
> width, but also the amplitude may be somewhat larger because it doesn't
> instantaneously go to the short-circuit value.  In any event, over a range
> of typical load capacitances, there is also interaction between the pulse
> duration and package impedances, such that the pulsewidth also figures into
> the amount of ground bounce you get (if the load capacitance is not so large
> that the width greatly exceeds the package time constants).
> 
> Regards,
> Andy


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