Thermal Protection
Protection that reduces or completely cuts the output when the board or power stage temperature exceeds a set threshold. Its difference from current protection is that it measures the effect, not the cause: whatever the reason, it sees the heat that has built up. Once cooling is achieved, the system usually returns to operation by itself.
The temperature is usually monitored with an NTC thermistor placed close to the power stage, or with a sensor inside the semiconductor. As the threshold is approached, some designs first reduce the current and then cut it off completely; that way the motion slows down instead of stopping abruptly.
Thermal protection engaging almost always points to a sizing or mounting problem:
- Running at the limit of the continuous current capacity.
- Mounting the module in a closed box with no ventilation.
- High ambient temperature; catalogue values are usually given for 25 °C.
- Motor current running higher than expected because of mechanical stress.
With repeated thermal shutdowns the solution is not to raise the threshold but to remove the cause: measure the current, ventilate the mounting, and move to a model with a higher continuous current capacity if necessary. Since the product data does not state an operating temperature range for AXI modules, the thermal margin must be verified by field measurement.
Where this term is used: DC Motor Driver Selection Guide