RS-232 Tx / Rx monitoring LEDs?
Brian L. Stuart
blstuart at bellsouth.net
Thu Aug 20 12:35:37 CDT 2015
On Thu, 8/20/15, Mouse <mouse at Rodents-Montreal.ORG> wrote:
> Maybe _rated_ current, but, even there, I don't think so (my TTL
> doc hasn't been unpacked yet, or I'd go check, but I'm fairly sure
> they are generally specced to sink more current to GND
> than source from Vcc).
It so happens I have a TTL handbook to hand at the moment. From
the 1985 TI TTL data book:
7400 -0.4 16
74H00 -0.5 20
74LS00 -0.4 8
74S00 -1 20
all in mA. So as rated, TTL devices can sink a solid order of
magnitude more current than they can source.
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