Originally Posted by Tim Wescott[_4_]

On Mon, 05 May 2014 13:06:33 -0700, Jim Thompson wrote:

On Mon, 05 May 2014 13:58:50 -0500, Tim Wescott
ly wrote:

On Mon, 05 May 2014 11:49:22 -0700, Jim Thompson wrote:

Temperature Step in a .TRAN Simulation?

Any clever soul out there figured out a way to do that?

...Jim Thompson

LTSpice or regular?



I'm pretty sure you can do it with a .STEP or a .TEMP command in
LTSpice.

.STEP isn't the same as a step in temperature _during_ the simulation
run.

.STEP simply applies a data change at the _beginning_ of a run.

I want, during a transient solution, to have a temperature change to
test a temperature-related shutdown mechanism.

I suspect I will have to do a replacement in subcircuits...

TEMP = V(MyTemp)

and fudge it with a voltage step :-]

Ooh ouch. So ideally you'd like to make sure that your temperature
detection/shut down works correctly as temperature is changing
dynamically?

I think I'd separate the circuit into part A and part B, where part A is
the temperature sensor and part B is the rest. Characterize part A over
temperature, fake its behavior in a subcircuit, then make sure that part
B responds correctly to the changes in part A at a variety of different
temperatures.

It'll probably be valid, unless the temperature shows strong gradients
across the chip or changes as rapidly enough to be close to the time
constants of any RC pairs.

--
Tim Wescott
Control system and signal processing consulting
Wescott Design Services