eldo_user

Electrothermal Simulation
Specifying an Electrothermal Simulation
.subcircuit mybjt c b e th
.model bjt50 bjt level=…
Q1 c b e bjt50
.tempnode th
.end
Anything connected on the thermal nodes is treated as a thermal device (not electrical) and part
of the thermal network (not part of the electrical network).
The thermal node does not have to be the last connection in the list. For example, you can
alternatively specify:
.subcircuit mybjt2 th c b e
.model bjt50 bjt level=…
Q1 c b e bjt50
.tempnode th
.end
Blocks (subcircuit instances) are connected using the same convention as in regular SPICE. For
example:
X1 out1 inp em th1 mybjt
X2 out2 inm em th2 mybjt
Rth th1 th2 10
The Rth thermal resistor creates a thermal coupling between transistors X1 and X2, connecting
their respective thermal nodes th1 and th2 together. As th1 and th2 are connected to the thermal
node (th) of the X1 and X2 blocks, they are no longer treated as regular electrical connections
(by contrast, out1 and out2 are) carrying an electrical voltage. Instead, they carry at all times the
temperature elevation of the X1 and X2 blocks. The temperature elevation is always measured
with respect to the global temperature (27 °C by default in Eldo), and can be interpreted in
degrees Kelvin or Celsius as it is a delta.
You can use the subcircuit X instance parameter STATUS_TEMPNODE to control the
temperature inheritance for that instance. For example:
.subckto foo a b c
.tempnode c
R1 a b 1 tc1 = 0.1
X1 a b foo2 status_tempnode=0
.ends
Because STATUS_TEMPNODE is set to 0, devices in X1 do not contribute to the power of
instance foo. X1 does not inherit the temperature of instance foo, devices in X1 are supposed to
be at the temperature of the circuit (.TEMP command). When STATUS_TEMPNODE is 1
(default), X1 contributes to the power and inherits the temperature of the instance foo. Setting
STATUS_TEMPNODE=2 provides an intermediate case: X1 inherits the temperature of the
instance foo, but does not contribute to the power of X1.
Eldo® User's Manual, 15.3 717