Does anyone have an LTSpice component model/symbol combo for the LM7812 and LM7912 regulators or know of an equivalent component that's already in the library?

TIA

 

The collection from @Bordodynov has such models.
For LTspice users. Libraries of models, examples, etc (ltwiki.org)

 

The collection from @Bordodynov has such models.
For LTspice users. Libraries of models, examples, etc (ltwiki.org)

Thanks

 

Does anyone have an LTSpice component model/symbol combo for the LM7812 and LM7912 regulators or know of an equivalent component that's already in the library?

TIA

I just use the voltage source.

 

I just use the voltage source.

Which does not, of course, simulate the operation of the regulator, such as its minimum operating voltage or current limit.

 

Which does not, of course, simulate the operation of the regulator, such as its minimum operating voltage or current limit.

SPICE’s current probe could tell you how much the circuit is using without having to simulate the regulator itself, and the figure to use for the dropout voltage should not be the exact figure calculated by SPICE for a single ”typical” regulator, it is the recommended value from the datasheet.

 

SPICE’s current probe could tell you how much the circuit is using without having to simulate the regulator itself, and the figure to use for the dropout voltage should not be the exact figure calculated by SPICE for a single ”typical” regulator, it is the recommended value from the datasheet.

Still don't see a good reason for not using the regulator model rather than an ideal voltage source (which a regulator is not).

For example, when using an LM317 regulator, the sim using the model is a good way to check that the resistor values you selected for the desired output voltage are correct.

 

Crutschow, don't feed the trolls.
He's just an attention seeking idiot.

 

Crutschow, don't feed the trolls.
He's just an attention seeking idiot.

Ad hominem attacks are not allowed here.

 

Crutschow, don't feed the trolls.
He's just an attention seeking idiot.

Ian0 is not a troll (and certainly not a idiot), he's a respected contributor to this forum.
We were just have a little side discussion about simulation models.

 

Still don't see a good reason for not using the regulator model rather than an ideal voltage source (which a regulator is not)

But is it going to tell you anything useful?
In order to get a valid SPICE output, one would also have to model the ESRs and ESLs of all the decoupling capacitors, and the resistances and inductances of all the pcb tracks.
If all the interconnects have zero resistance and inductance, and all capacitors are perfect, then the voltage source might just as well be perfect.

Using a LM317 as a constant current load for a voltage amplifier would perhaps be a situation where SPICE’s opinion might be useful, or if I were making a “home-brew” regulator out of a zener and a few transistors.

 

Hi Derek,
This zipped file contains the 78 and 79 series.
Do you know how to create model symbols from these text libs?

E

 

But is it going to tell you anything useful?
In order to get a valid SPICE output, one would also have to model the ESRs and ESLs of all the decoupling capacitors, and the resistances and inductances of all the pcb tracks.
If all the interconnects have zero resistance and inductance, and all capacitors are perfect, then the voltage source might just as well be perfect.

But a voltage source device is too perfect--infinite current. An LM317 regulator is not.
An overload during simulation wouldn't cause "smoke", but would cause large voltage drop at the output.
That could be useful information.

 

But is it going to tell you anything useful?

Yes.
It shows If your supply voltage is sufficient to generated the desired output voltage, and if it will deliver the desired output current.
You can also check its dissipation to see if it needs a heatsink.

 

Hi Derek,
This zipped file contains the 78 and 79 series.
Do you know how to create model symbols from these text libs?

E

Nope, but I am sure I can find out. Thanks

 

But a voltage source device is too perfect--infinite current. An LM317 regulator is not.
An overload during simulation wouldn't cause "smoke", but would cause large voltage drop at the output.
That could be useful information.

But a designer would already know that. SPICE's current probe would tell you if a circuit was taking more than 1A, but a 7812 SPICE model would not collapse the output until well above that, when the regulator was operating beyond its design spec.

 

Yes.
It shows If your supply voltage is sufficient to generated the desired output voltage, and if it will deliver the desired output current.
You can also check its dissipation to see if it needs a heatsink.

The SPICE model has a dropout voltage of 1.9V. The datasheet says 2.0V typical, so 50% of devices would have a dropout voltage of more than 2V. Designing by the datasheet would produce a more reliable design than designing with the SPICE model.

 

ltspice-misc/models/regulators.lib at master · kafana/ltspice-misc · GitHub

The company owning the software does not provide each component. The LM78xx is one of those hassles.
The spice model modification happens however power supply improvements are more common.
Using the LM317 and LM337 by changing one resistor from adjustable to fixed value the simulation should be close enough
that it warrants an interlude with spice model programming. I think about regulator circuits as modules.
Linear Regulator Calculator - Power Electronics Calculators and Tools (eepower.com)

If it is noise then noise is simulated and mitigated.

 

Designing by the datasheet would produce a more reliable design than designing with the SPICE model.

The same can be said for any Spice model.
So we don't need to use Spice models for any active circuit element.

 

But a designer would already know that. SPICE's current probe would tell you if a circuit was taking more than 1A, but a 7812

But in good model, an overload would "jump out", prompting the designer that something is wrong.

SPICE model would not collapse the output until well above that, when the regulator was operating beyond its design spec.

Not necessarily true. Depends how good the model is.