How is output current limiting implemented in Pulse-Width Modulator (PWM) controllers?
Most PWM controller ICs provide current-limiting protection by sensing the power switch current. If the current-sense input exceeds a specific threshold, it terminates the present cycle (cycle-by-cycle current limit). Circuit layout is critical when using a current-sense resistor, which must be a low inductance type. Locate the capacitor associated with the current-sense filter capacitor very close to, and connected directly to, the PWM IC pin. Also, all the noise-sensitive, low-power ground connections should be connected together near the IC ground pin, and a single connection should be made to the power ground (sense resistor ground point).
