Thermal Simulation of Linear RegulatorsThermal Simulation Circuits and Method for Linear Regulators

Simulation Circuits for Thermal Simulation of Linear Regulators

The following table shows simulation circuits currently available for thermal simulation of linear regulators. The lineup includes output voltages of 3.3 V/5.0 V and output currents of 200 mA/500 mA.

These linear regulators feature an input voltage range of 3 V to 42 V and a wide operating temperature range of -40°C to +150°C. They are automotive-compatible and can be directly connected to an automotive battery. The output voltage accuracy is as high as ±2% and the quiescent current is as low as 38μ to 40μA (typ.). In addition, only two external components are required: an input capacitor of 0.1 μF (typ.) or more and an output capacitor of 10 μF (typ.) or more.

Example of Simulation Circuit

Simulation Circuit (BD433M2EFJ-C)

In the above figure, the area within the green line shows a thermal simulation circuit; the rest is an electrical simulation circuit. The thermal simulation circuit calculates the temperature of the BD433M2EFJ-C linear regulator by modeling the device losses calculated by the electrical simulation and the linear regulator mounted on a PCB for thermal simulation. The blue line in the upper right graph shows the junction temperature (\( T_j \)) of the IC. After startup, the junction temperature rises with time, and after about 600 seconds, it stabilizes at approximately 66°C.

How to Run Simulation

To run a thermal simulation, click the Run icon ▶ shown above. Simulation conditions can be set from the Simulation Settings icon. In the initial state, the simulation conditions have already been set and the simulation results are displayed. If you run a thermal simulation after changing the simulation conditions, the temperature graphs and other data will be updated.

This article is based on the following “User’s Guide: Thermal Simulation of BD4xxMx Series of Linear Regulators.”

https://fscdn.rohm.com/en/products/databook/applinote/ic/power/linear_regulator/bd4xxmx_thermal_simulation_ug-e.pdf