Abd ul-Rahman Lomax wrote:
>
> At 10:23 AM 3/14/01 +0100, [EMAIL PROTECTED] wrote:
> >As chip designers tend to show
> >ambition in specifying three and more power supplies for one chip,
> >there is not much use in the hidden pin feature any more.
>
> The vast majority of integrated circuits in designs which cross
> my desk are single-supply, and the majority of designs have only
> two power nets: ground and one other.
And as has been demonstrated so many times, one person's experience with
designs is vastly different from an other's!
A design I am currently working on has five digital power supplies
(5.0, 3.3, 2.5 1.8 and 1.2) as well as two analog supplies. The design
uses several SN74LVC14A Schmitt-trigger inverters for cleaning up some
slow edges. Interestingly one SN74LVC14A provides 6 inverters, which is
how many are required on the board; however, I need 2 at 3.3V, 3 at 2.5V
and 1 at 1.8V. Using the hidden pins would be a killer, as would just
allowing individual gates. So the three 14-pin packages are used in
their entirety to insure that the next guy to "just add an inverter" has
to decide which of the 3 packages he intends utilize.
I do have designs where I use hidden pins, but (for me) they are getting
rarer.
As to the rest of Abd's message, I agree wholeheartedly:
> Further, it should be considered that there is a huge base of
> legacy designs which would be wrecked if Protel no longer
> supported hidden pins.
> *But* it would not be difficult to provide tools that would make
> the use of hidden pins less hazardous, or the elimination of
> hidden pins in a design easier.
Yes! Yes!
Except for the following:
> A warning that there are hidden power pins on a design would
> not be a bad idea.
With this sentence, I totally disagree with Abd, I think,
"A warning that there are hidden power pins on a design
*should* be REQUIRED!"
David W. Gulley
Destiny Designs
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