Are you not using all four D inputs?Also, do the 1d-4d inputs need a resistor or will the internal resistors take care of it.
The datasheet I looked at says IIH=20 microamps max when VI=2.7V. This is not a max allowable value. It is the maximum current the input will draw when the input is 2.7V. This spec is given so you will know how many inputs you can connect to the output of another device without overloading it.Are you sure? The data sheet said the maximum high level input current was 40 nano amps.
I have never seen a TTL or CMOS IC that requires resistors to apply logic levels to undriven or unused inputs.Is this true for many other ttl ics, including ram and binary counters?
That will work with CMOS, but it is not necessary. With TTL, 10k resistor pulldowns WILL NOT WORK. The input currents will make the input voltages high enough to be perceived by the IC as logic highs.I'll have to chime in here since my project uses some logic and am still learning. While most forums say no resistor is necessary, the three books I just bought on logic chips say the opposite.
They say to connect the unused inputs to each other and then to a ~10k resistor to ground. So if the O/P is reading one of the newer logic how to books, I can see his confusion.
Below is an excerpt from the 7400 Series wiki:Aren't all of the latest (produced in the last couple of years) TTL logic, Cmos or Dmos internally? Even though they are still called TTL?
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by Jake Hertz
by Jake Hertz
by Jake Hertz