3 Dec
2006
3 Dec
'06
1:44 p.m.
the normal totem pole output for S TTL logic will only sink 20 ma to
guarantee a logic low. The 220 ohm resistor to +5 will be 22.7ma, so
you are exceeding the chip's capability by some amount. LS and HCT
can sink even less current.
best regards, Steve Thatcher
At 01:02 PM 12/3/2006, you wrote:
I know the "right" answer to this one--you
drive 220/330 ohm
terminated loads with 7438-type OC drivers. But, going a bit afield
from "correct", can one drive a single 220/330 ohm terminated load at
the end of a 3m length of ribbon cable at 1 MHz using plain old totem-
pole STTL output? How about an LSTTL or HCT totem-pole driver?
You can assume that the receiver is a 74LS14.
Thanks,
Chuck