11 Mar
2005
11 Mar
'05
6:07 p.m.
Well - the spec for the LS121 is pretty well-known.
Someone with more
IIRC, the pulse width is something like 0.7*R*C
caffeine and inclination than I might well look up the
datasheet and
work out what the value ought to be. It looks like it says "270"
overscribbled with "220" to me - what units I don't know. Try 220nF.
If that doesn't work, try 220pF. You'll be in the ballpark with one of
those.
Assuming R is within the recomended range for the IC, you are not going
to get a 5.5us pulse (which sounds about right) with a 270nF cap. 270pF
could well be right.
-tony