> TPICxxxBxx

B and other revised silicon versions of nearly ALL chips I've ever seen
(except standard 4xxx(x) CMOS where the B means buffered - see below)
have higher speed and lower noise immunity than the original chips they
are supposed to improve. The reason is die shrink which causes higher
speed operation and much steeper thresholds usually, and this means
glitches and critical layout will kill your design.

For these and other reasons I *swear* by the old 4xxx(x) (no HC no C no M
no nothing) series of logic chips. You get one of those misbehave without
using a nuke, tell me. Meters of unshielded clock trace routing and
nothing happens. At about 5 MHz (@ 5V) these chips are deaf. Glitches ?
What glitches ?

So in the context of this thread I use CD4094 and external buffers (ULN...
or discrete) for this. *Never* seen a problem. Sometimes I have circuits
running in the same shield box as RF and power hardware at +10dBm and
more, and still no problems.

just thought I'd mention this ;-),

Peter

PS: The CD4094 is second sourced by almost everyone you'd be able to
quote. Plain CD4xxx(x) chips are short circuit proof both against GND and
VDD and won't kill the supply even if it's a weak battery in either case,
nor will they burn if shorted (and I mean ALL outputs shorted - they get
lukewarm at best). In other words, a dream. That's why they threaten to
discontinue them probably. Gotta be logical, no ? Who needs such things
that are undestructible and work forever ? Mo money to be made on such
fabs. Kill them. Yeah.

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