eldo_user

Electrothermal Simulation
Verilog-A Support
• Eldo Premier is not able to deactivate, on the resistors belonging to the thermal network,
the automatic MINRVAL=1e-3 added by default with option PREMIER_MODE=2. If
the thermal network has resistors with very small values (below 1e-3 Ohm), it is advised
to explicitly set the MINRVAL option to avoid them being removed.
Related Commands
• .TEMPNODE command in the Eldo Reference Manual.
• .REPORT_HEATING command in the Eldo Reference Manual.
• .SUBCKT command in the Eldo Reference Manual.
• Subcircuit Instance in the Eldo Reference Manual.
Related Topics
Reporting and Sorting Thermal Contributors
Electrothermal Simulation Example
Verilog-A Support
Electrothermal simulation supports Verilog-A models. The power contribution of Y instances
are taken into account. Eldo simulates Verilog-A models in an electrothermal simulation, in the
same way as for SPICE devices.
For Verilog-A devices, the analog kernel parameter system function $temperature, returns the
local temperature in (Kelvin units) of the given subcircuit. Verilog-A devices that have
temperature dependency are then impacted by any temperature variation inside the surrounding
subcircuit. In a standard (non-electrothermal) simulation, the $temperature will always return
the ambient temperature of the circuit.
To simulate coupled electrothermal effects in Eldo, a thermal node for a given subcircuit is
defined and connected to a thermal network in two ways using the .TEMPNODE command:
internal definition inside the subcircuit and external definition outside the subcircuit. The
electrical behavior of all instances inside such a subcircuit that are temperature dependent, are
affected by the local temperature of this subcircuit. The total power dissipated by the
instantiated devices, contributes to the heating in the connected thermal network.
• Explicit .TEMPNODE specification:
In the same as for Eldo devices, a Verilog-A model can be instantiated in a subcircuit
that contains a .TEMPNODE command that describes the additional thermal port. The
thermal port must be connected explicitly to the thermal network to enable
electrothermal simulation.
In the first example below, a SPICE resistor is replaced by a Verilog-A instance.
• Implicit .TEMPNODE specification:
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Eldo® User's Manual, 15.3