[Scene_Cast2]

How do I add a voltage other than a 9V battery?

What are the current alternatives to this? I'm looking to build an LED driver (possible IC candidates are Linear LT3477, TI TPS63020 and some other TI / Linear chips). I'd kill for a software that would simulate any chips (or even just a crude approximation of them).

[compumike]

This is an issue we've been tackling at CircuitLab (https://www.circuitlab.com/), and the fundamental issue is that the chip makers (Linear, TI, Analog Devices, etc) don't want to let their device models out of the building. They often do have simplified models for simpler parts (op-amps), but for more complex mixed-mode parts (switchers), coverage is sparse, and a SPICE netlist is a poor language for encoding the control logic. LTspice, for example, includes encrypted models for many of their switching power supply parts, and those include special non-standard SPICE behavioral components to make the models possible to execute in a reasonable amount of time. Other companies with web-based / server-side simulation keep the models entirely opaque and tremendously limit your ability to configure the surrounding components. The goal is to get you just far enough to have confidence that their chip is the solution for you, and then get you to use their tools and field application engineers. This is the status quo and they're generally not in any rush to disturb it.

[nullified]

LTspice [0] is an excellent (and might I add free) SPICE simulator. Linear includes proper models of the majority of their chip lineup, including LED drivers. Their power supply IC models are also excellent. You can simulate a full LED driver circuit and a whole lot more with LTspice. TI also has a similar SPICE simulator [1], but it's not nearly as good, and its simulations are much slower and a bit more unreliable.

I design electronics for a living, and I use LTspice all the time for power supply and analog circuit simulations.

[0]: http://www.linear.com/designtools/software/#LTspice

[1]: http://www.ti.com/tool/tina-ti

[vonmoltke]

Worth pointing out too that most major semiconductor vendors provide SPICE models for their parts. Maxim, for example, has an extensive set of models for their chips: http://www.maximintegrated.com/design/tools/modeling-simulat...

[Scene_Cast2]

Thanks, that helps a lot! Giving it a shot right now.

How long should it take to make a high-power (3A+ @ 3V, buck-boost IC) LED driver, very approximately?

[nullified]

If by "make" you mean create the schematic in LTspice and simulate it, then I would guess about an hour or two (mostly because this might be your first time using LTspice). If Linear has a part that already meets those requirements, it should be a very straight forward affair.