I'm trying to simulate a temperature sensing schematic with a latching function (meaning that the schematic should go to overtemperature mode at let's say 75C and go back to normal at 50).
I can do a temperature sweep function with the command
.temp 25 50 75. I see that the schematic responding well (I see that the forward diode voltage going down with a rate of -2mV/C as expected). But this means that the LTSpice engine does regular transient analisis for each temperature I'm giving, which stays constant over all the simulation time.
Actually I'd beter do only ONE transient with a temperature changing over the analisys time. I could pick a voltage source to be a temperature set point or may be there is a SPICE command that will tell the engine what I actually want to do with a temperature?
I see some models that containing another one pin representing the temperature of the chip. It can be connected to the heat sink with a capacitors (standing for corresponding thermal capacity), resistors (standing for correcponding thermal resistance). This technique looks very powerfull and accurate, but I will definitely struggle to find all needed components with this kind of thermal model, do accurately all thermal elements including heat sources. I don't actually need all this accuracy right now - all I need is to verify that the thermal protection will work fine at some certain points.