Tim Mascorella asked,
> the cathode side of a diode with a square pad on the circuit board, while
> others say the convention is just the opposite. Which is it, and is there a
> specification which mandates one or the other?
I'm not aware of any actual standard. Maybe one exists and that's
my problem!
There's actually alot of boring history to this question. In
the '70s, as we migrated to CAD equipment, hand written netlists
were required. Generally the CAD equipment needed to think in
terms of pin numbers, leading to a general convention of labelling
the cathode end of a diode, or the "+" end of a polarized capacitor,
as pin 1, usually accompanied with a square pad.
As CAE equipment rolled out, many such vendors supplied at least
a starting library. As far as I can tell, all but Futurenet used
the cathode-as-pin-1 approach. These days, I think a few CAE ven-
dors are using pin-2-as-cathode, notably Viewlogic.
These days, LED's tend to complicate things, as they tend to be
marked from the manufacturer with a "+" on the anode end.
Our standard advice to customers is "never use a vendor supplied
library", unless you one-by-one qualify each symbol.
Perhaps I am simply a victim of history and should follow the LED
and Viewlogic model.
"The simple things you see are all complicated"
- The Who
Regards,
Jeff Seeger Applied CAD Knowledge Inc
Chief Boring Historian Tyngsboro, MA 01879
[log in to unmask] 508 649 9800
***************************************************************************
* TechNet mail list is provided as a service by IPC using SmartList v3.05 *
***************************************************************************
* To unsubscribe from this list at any time, send a message to: *
* [log in to unmask] with <subject: unsubscribe> and no text. *
***************************************************************************
|
