I wrote:
I think you misunderstood. The macro-model contains FAKE elements
that stand in for whole sections of transistors and stuff.
rainbowsally replied:
Understood. But they can be recreated using discretes. This truly
isn't a problem.
I hope I am neither offending, nor coming off sounding like a jerk ...
but I am still not sure you understand.
Let's say someone hands you a SPICE model for an IC, part number XYZ,
which you want to use in your circuit, and simulate in LTspice.
But being the curious type, you need to know what is in that model.
You want to see it visually in schematic form. So you spring for that
$100K conversion program which converts it into a schematic. And,
voila, it spits out a schematic consisting of:
a couple of voltage sources,
a few resistors and capacitors,
and a behavioral controlled source described by an equation.
Not a transistor in sight! In other words, it is one of those dreaded
"macro-models" that represents the behavior (rather than the
structure) of the XYZ part.
Sure, you could replace it or recreate it using discretes ... if you
knew what discretes to use! But you don't. All you have is the
macro-model. You know nothing else about the insides of this XYZ
part.
For that TLC555 that started this discussion, if the SPICE model you
have is one of these macro-models, then you might have no way to
understand why the input current is the same as it was for an old
NE555, even though the TLC555 is supposed to be a CMOS part.
Furthermore, it truly is a problem when the macro-model does not
accurately represent a certain behavior of the device that matters to
you. And that can easily happen.
Andy
