I am trying to simulate a Dflop on LTspice and it does not work. I look the other post on this subject and I didn't get what was the problem.
Here is the simulation It is like there is no clock. The IC is not taking into account the clock.
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What is V5 set to? – Renan Jun 12 '22 at 13:38
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@Renan Edited ;) – Jess Jun 12 '22 at 13:39
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1I had CLR and PRE connected via pull-ups to 5 volts on the earlier answer but, some sims may have the logic of these inputs the other way round. Experiment with both until it works. But, you do need to have both these pins connected to a logic level. – Andy aka Jun 12 '22 at 14:07
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1@Andyaka I tried ... anything work. Normally the CLR pin is by default set at the GND – Jess Jun 12 '22 at 14:13
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1Not in microcap. – Andy aka Jun 12 '22 at 15:04
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1In microcap their full pin name is CLRB and PREB where the B part means "bar" or inverted. – Andy aka Jun 12 '22 at 15:27
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First of all, the preset and clear pins are not the power supply. They are active high (should be 0V for the FF to work) and the voltage should be set via the SpiceLine (set to e.g. "Vhigh 5 Trise 1n", by right-clicking the component):
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1Ok i got it. I was not thinking that the PRE pin was setting the output voltage. – Jess Jun 12 '22 at 14:21
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3@Jess Just one mention: if the 8th pin of any A device is left floating, it will default to being connected to node
0(ground). Every other pin that is left floating is connected (internally) to the 8th pin, whichever connection that may be. In this case, since you are not using a custom ground, you can leavePREandCLRunconnected and they will be tied to ground, since the 8th pin is floating (see the help under LTspice > Circuit Elements > A. ...). – a concerned citizen Jun 12 '22 at 15:08 -
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