I have a small problem with small parts in a small area on a small board
(so what else is new?).

I have 4 parallel channels of a Quad Transimpedance Amplifier circuit,
which is very high gain and requires good isolation. The circuit is all
descrete analog components, mostly 0402, except for the S0-8 op-amps,
and is packaged quite densely with only .020" between components in the
tight spots, and no room for package outlines. The circuit is layed out
very nicely, and is electrically excellent, but unfortunately, there is
no room for designators.

Most of these boards are built in house, but the error rate on stuffing
components (the wrong ones in the wrong locations) is very high and the
trouble-shooting time to find these assembly errors is exhorbinate, so I
really do need the silkscreen every place I can get it.

Herein lies the problem. I have 4 duplicate channels, with ref
designators currently numbered as R1_1, R1_2, R1_3, R1_4, R2_1, etc. in
the 4 parallel and identical channels. My ref designators are already as
small as our fab house will go for which is .025" high and .005" thick
lines, and I am also tenting all of my vias so that they will not
interfere with the silkscreen. I could however get a lot more
designators placed in the limited room that I have if I could eliminate
the channel designator part of the ref designator, i.e.: reduce the R1_1
to simply R1, which is much shorter, and which due to the layout is
acceptable since the channels are physically very clear and already
labeled as CH_1, CH2, etc.

However, if I shorten the actual designator, it makes for
synchronization problems with the schematic, as well as hell to pay in
the DRC department.

I want to keep the ref designators the same for the same component in
the different channels for the sake of circuit / schematic /
troubleshooting clarity, etc. Renumbering them to 100 series for channel
1, 200 series for channel 2, etc, is not only very time consuming but
doesn't really get me much shorter designators anyway.

Hiding the original designators, and replacing them with "loose" text is
not only very time consuming, but prone to error, not only now, bur
especially in the future if someone else has to modify the board and
move components, since the "loose" text is not related to the component.

I have thought of copying off the final database and modifying all of
the designators and then generating a new gerbers from the modified file
and substituting those overlay gerbers in the final set for fab, but
that is a massive amount of work that will have to be done all over
again if there is any substantial change to the board.

I do in fact own an Official Mickey Mouse Club Tee Shirt and Hat, which
I am about to pull out and put on, but there has got to be a better way
of handling duplicate circuits in Protel, or should I just throw up my
hands and look for another product all together (PADs, Mentor, Verybest,
etc.). It appears that Protel truly has no provision to handle any kind
of duplicate circuits, especially of the Step and Repeat variety,
whatsoever.

Anyone out there got any useful ideas?

JaMi Smith

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