> TPIC6595    250 mA / output  (works great, I use LOTS of these
> parts) TPIC6B595   150 mA / output  (I have had problems with this
> variant) TPIC6C595   100 mA / output  (pin compatible with 74hc595)

Don't forget the other one:

TPIC6A595  350mA / output

I use these in 2 designs and have had no failures or glitches so far.
Having used the original TPIC6595 (with which I did have glitch
problems, but only when using an in circuit emulator!) I went
overboard this time in my layout and think I got it pretty bullet
proof. The chip susceptability to glitches problem raised in this
thread has got me curious though, and I should take some time to try
some similar tests.

The cool thing about the A chip is that it handles a reasonable
amount of current (without even getting warm) and has output short
circuit protection that works (starts chopping the output around
0.8A). I have tested the short circuit protection by loosely shorting
12V loads with a wire, have tried inductive loads with and without
diode protection and they behave nicely. I recommend using diodes on
inductive loads though to reduce EMI.

It is a nuiscance the parts are all different pinouts, but that's
life
I guess. Probably related to getting a layout that works well in
practice, given the glitch issues. Originally I was worried about
supply from just one manufacturer, but I found that Allegro make a
compatible part (A6A696KA and A6A595KLB). In summary: very nice chip,
a little expensive, but worth it for peace of mind about short
circuit
protection and for minimum component count over other solutions.

Another interesting chip to look at is the Motorola MC33298 with 8 x
1
Amp outputs, ~4A current limiting, plus fault reporting features. A
little more expensive again, but a number of extra features.

Brent Brown
Electronic Design Solutions
16 English Street
Hamilton, New Zealand
Ph/fax: +64 7 849 0069
Mobile/txt: 025 334 069
eMail:  brent.brown@clear.net.nz

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