[SI-LIST] Re: Calculation to determine SSO pushout in time
- From: Neeraj Pendse <cnepsc@xxxxxxxxxxxxxxx>
- To: ron.mancuso@xxxxxxxxxxx
- Date: Thu, 11 Oct 2001 14:29:15 -0700
Ron:
If you have a good idea of the parasitic values of your interconnect,
and a SPICE or similar solver, this should be pretty easy to do for
lumped or distributed lumped interconnect
1. Get a field solver, or just formulas from an electronic handbook to
create a partial inductance based model of the interconnect. Is the
interconnect is long, I would recommend using several pieces in a
distributed lumped model. Although you could use formulae to do that,
this kind of stuff is best left to a field solver. The model should
include the IO power network.
2. Input the RLC model into a SPICE like simulator, and run it with the
right drivers (do pay attention to your power supply model and the
driver/receiver models)
Pretty soon, based on back of the envelop calculations and SPICE, you
will come up with a voltage droop/bounce per IO. Given the fact that you
know what are you limits for drivers VDDIO and VSSIO, # of SSOs per
supply line cvan be derived.
Hope that helps!
- Neeraj.
National Semiconductor Corporation
2900 Semiconductor Drive, Mail Stop 19-100
Santa Clara, CA 95052.
http://www.national.com/, NYSE: NSM
Ron Mancuso wrote:
>
> I'm looking for input on how to recommend a power/ground to signal ratio
> with respect to SSO pushout.
>
> I understand that number of simultaneous switch outputs, slew rate, pad
> and lead C, pad and lead L, delta V, and load C are the main factors -
> but I don't know how to bring all of those in for a pushout number.
>
> Can anyone help?
>
> Thanks,
> Ron Mancuso
> Corrent Corporation
>
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