eldo_user

Electrothermal Simulation
Specifying an Electrothermal Simulation
• Subcircuit X instances inside a .SUBCKT inherit the .TEMPNODE of the parent, unless
a new .TEMPNODE is specified on the .SUBCKT definition of the child, or the
parameter STATUS_TEMPNODE= 0 is specified on the X instance (to disable the
electrothermal effect for that instance).
• You can use the subcircuit X instance parameter STATUS_TEMPNODE to disable (0)
or enable (1—default) the temperature inheritance for that instance. Alternatively, you
can select an intermediate case (2) where the subcircuit instance inherits the temperature
as computed by the electrothermal simulation, but the instance does not contribute to the
electrothermal power. This is useful in applications using LED models where the
forward current is split into two components: one component contributes to dissipation
(self-heating), the other current component is associated with light output without any
contribution to heating; but both components depend on the local junction temperature.
• Temperature-dependent parameters present inside a .SUBCKT with .TEMPNODE are
re-evaluated at each iteration, and their values are propagated.
• DTEMP specifications on devices inside an electrothermal subcircuit are ignored (Eldo
computes the DTEMP value).
• For external definition syntax, if there are multiple .TEMPNODE commands specified
for the same subcircuit only the last one is used, the others are ignored.
• For external definition syntax, if the thermal pin of a subcircuit instance is connected to
nothing or to ground, then electrothermal simulation is disabled on this subcircuit
instance.
• For external definition syntax, the subcircuit name can contain wildcards. In this case, a
thermal node is created for each subcircuit matching the regular expression.
• For external definition syntax, when using wildcards, it is advised to carefully select
subcircuits where the thermal node will be really connected to a thermal network. For
example, it is not advised to specify:
Limitations
.TEMPNODE subckt=* thnode=th
when only a few subcircuits will be connected to a thermal network. Adding a dangling
thermal node on subcircuits where electrothermal simulation will not be activated has a
negative impact on performance.
• For Monte Carlo analysis: DEV is not allowed on parameters used on .SUBCKT with
.TEMPNODE, however DEVX is allowed.
• Electrothermal simulation is disabled when performing AC analysis: but DCOP done
prior to AC does take into account electrothermal effects.
• Electrothermal simulation is disabled when either IEM or RF analyses are found in the
circuit.
Eldo® User's Manual, 15.3 719