The current limiting function protects the IC and downstream devices when an overcurrent flows in.
The output current—output current characteristic of the voltage regulator current limiting function when the current limiting function activates differs depending on the product. A feedback circuit (fold back curve characteristic) is generally used, but other types include the drooping characteristic, a combined drooping and fold back type, etc.
This section explains the actual current limiting operation for a product with a maximum output current of 200mA using fold back characteristic current limiting as an example.
|Point a – Point b||The output current increases from 0mA toward the right side.|
|Point b – Point c||The maximum output current exceeds 200mA, and when it reaches 260mA the current limiting function activates.|
|Point c – Point d||The output current is restricted as the output voltage decreases.|
Finally, the output short-circuit state (0V) is reached and the output current and the output current becomes the short-circuit current of 50mA.
The heat loss during the short-circuit is calculated as input voltage x short-circuit current, and is held to VIN 4V x 50mA=200mW.