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June 1998

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Subject:
From:
Mike Holmes x4356 <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 16 Jun 1998 07:54:48 -0400
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----- Begin Included Message -----

From: Mitch Morey <[log in to unmask]>

We (internally)have a growing debate going on in regards to reference
designators. We have (long ago) adopted IEEE 315 as the "bible" for
schematic symbol and reference designators, but the standard seems
misleading.

Take for instance OP-AMPs should have "AR" as the designations,
OSCILLATORS should be "G", ATTENUATORS should be "AT" according
to how you interpret the standard.

But, aren't these all, in fact, microcircuits ("U") or integrated-circuit
packages in today's practice? Does anyone else have a better system
for defining reference designators, per "some" standard? It seems IEEE-
315/315A should have been out-dated long ago.

Help?

Mitch
----- End Included Message -----
Mitch,

        As a (used to be) drafting checker, this subject always was a favorite
of mine. In selecting which reference designation class letter, one should use
the following algorithm:

        Is there a specific class letter? AR, AT, G in your query. If so then
        use it.

        If ther is no specific class letter, is the component normally
        disasseble-able without damage? If yes, use A, if no use U. U is not
        a specific class letter for microcircuits but most microcircuits
        do not have specific class letters and can not be disassembled without
        damage thus the use of U.

                         |
                        /|\
                       / | \
                      /  |__\      /\
                     /____@_\      |
                  ~~[________)~~
~~~~~~~~~~~~~~[]~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Michael L. (Mike) Holmes
Charter Member, Space Coast Chapter, IPC Designers Council

                                MS 1-5852
Designer 3                      Harris Corporation
PWB Design Group                Government Communications Systems Division
Digital and Electronic          2400 NE Palm Bay Road
Packaging Section               Palm Bay, FL 32905
*****************************************************************************

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