**From:** Ingraham, Andrew (*Andrew.Ingraham@compaq.com*)

**Date:** Tue Oct 10 2000 - 18:07:44 PDT

**Next message:**Doug Brooks: "RE: [SI-LIST] : Current flow limit for wire bonding"**Previous message:**Todd Westerhoff: "RE: [SI-LIST] : JEDEC HSTL and SSTL_2 standards compliance"**Maybe in reply to:**Bill Cohen: "[SI-LIST] : Variability of Supply voltages"**Next in thread:**Bill Cohen: "RE: [SI-LIST] : Variability of Supply voltages"

*> Can we assume that when one power supply is at a maximum the other two
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*> supplies
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*> will be at a maximum?
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No, as already described. There might be some interrelationships, but in

general, one should start by assuming that the three supply voltages are

unrelated; then later prove how and to what degree they aren't.

*> Should we assume that all three supplies can be
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*> independent and we need to perform a maxtrix of 9 combinations to do
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*> a proper worst case analysis?
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Well, that depends. If you know for some reason that the only interesting

cases to look at, are when all the supplies are at minimum, or all at

maximum, then maybe you could skip the other combinations, or some subset of

them. It may be that the other combinations are uninteresting as far as the

overall worst-case results are concerned. Or maybe not. A lot depends on

what goes on around the boundaries between the supply voltages. Margining

one low and the other high might cause significant pulsewidth shrinkage, for

example, which you would otherwise miss. To cover all the bases that

actually happen with your real circuit, you should do them all.

Andy

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**Next message:**Doug Brooks: "RE: [SI-LIST] : Current flow limit for wire bonding"**Previous message:**Todd Westerhoff: "RE: [SI-LIST] : JEDEC HSTL and SSTL_2 standards compliance"**Maybe in reply to:**Bill Cohen: "[SI-LIST] : Variability of Supply voltages"**Next in thread:**Bill Cohen: "RE: [SI-LIST] : Variability of Supply voltages"

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