NE555 seems to have changed in one of the LtSpice updates?

Question

Today I dropped the NE555 on the form and noticed the OUTPUT was matching the Vcc? This isn't correct and I am sure this has not been this way in the past.

Also, when I use a pull up R from another source to lift it higher, which also used to work, it simply current sinks it at the Vcc of the chip..

The output of the timer on when is suppose to be a emitter follower and thus allows you to pull up with external R's to account for the Darlington loose that's in the original design.

I am sure I would of noticed this way earlier because i've done lots of things with the timer in LT and many times the output voltage was calculated in the design, except this time, there is a problem!

I did a Ltspice update i think couple of weeks ago..

Is there any way to check the status on the model as when and if it was updated?

currently I have the RESET tied high and I am simply using the threshold and trigger inputs tied together as a window switch for a feed back current sense.

Jamie

Miguel Giménez · Accepted Answer

The last entry about NE555 in the change log is:    06/06/08 Revised the NE555 model. so the change is (almost) six years old. --  Saludos

Maynard A. Philbrook Jr. · Answer

Ok, well it seems if I loaded the output down I can get it to show the drop however, there seems to be a issue here because the real deal drops very quickly to 1 diode drop and then when loading it near 200mA, it may get down to almost 2 diode drops, which is fine in most cases..

It's just seems weird that all of a sudden I don't need to use a Vcc to output R to bring the output up the Vcc with the model now? I tested an original LM555(Yes I have some) and it does drop it's output like it should in the original design. I am not saying that it's a good thing, I am just saying the model is trying to improve on what isn't

Jamie

NE555 seems to have changed in one of the LtSpice updates?

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