[sdiy] Hex display 7 segment drivers Fairchild DM9368N

[Robin Whittle]

The 9368 was a TTL driver chip with a 4 bit latch and 7 segment driver
for common cathode displays.  It did 0 to 9, A, B, C, D, E and F.  With
more recent displays (after the late 1970s, which I guess was when the
chip was designed) which are higher efficiency, its internal current
limiting system was rather bright, so it was best to run 220R or similar
in series with each output pin.

Maybe the 9368 was also made by Signetics.  This app note mentions it as
being Fairchild, but neglects to mention its hex ability:

  http://www.denizyildirim.org/mylibrary/docs/led-display-drivers.pdf

Here's the datasheet:

  http://socrates.berkeley.edu/~phylabs/bsc/PDFFiles/DM9368.pdf

It could also blank leading zeros.  This datasheet is from 1998, which
surprised me, since the last I bought were in the early 1980s and I have
kept my eyes open for them since.  The latest date code of one I have
here is 8306.  It is identified as "9368PC".  Its no longer a product at
http://www.fairchildsemi.com.

This version of the datasheet was revised in 2000:
	
  http://wenku.baidu.com/view/bf3885030740be1e650e9a3e.html

so maybe someone has stock of these marvellous chips somewhere.

DM9368N is the plastic package version.  Digikey lists them, but there
is no stock.  Octopart:

  http://octopart.com/dm9368n-fairchild%2Bsemiconductor-444502

lists them as being available from Digikey.  I found only one supplier
which had both stock and prices:

  http://www.littlediode.com/components/FR_DM9368N.html

for UKP18.99.  A Hong Kong supplier has 9 of them for USD$9.99 each,
which I think is a good deal:

  http://www.ebay.com/itm/270841674128

A few other eBay sellers have them, including 190600833374 for USD$9.

Searching for 9369PC was more fruitful:  390366273961  6 for USD$5.95
each and this one, which is a beauty, from California: 260929713623 20
auctioned with a USD$9.99 minimum bid.  The photo is of another chip,
but I assume they know what they are doing.

Probably a GAL could be programmed to perform 4 bit to Hex 7 segment
decoding.  http://stores.ebay.com/IC-China has 16V8, 20V8 and 22V10
Galls cheap in lots of 10, plus cheap EPROMs too.  Of course an EPROM
could be programmed to do Hex decoding.  It would be rather bulky, but
it might work OK for pulling the segments up or down.

  - Robin          http://www.firstpr.com.au/rwi/dfish/