8.3.9.1 High-Side MOSFET Overcurrent Protection

The device implements current-mode control, which uses the internal COMP voltage to control the turnoff of the high-side MOSFET and the turnon of the low-side MOSFET on a cycle-by-cycle basis. During each cycle, the switch current and the current reference generated by the internal COMP voltage are compared. When the peak switch current intersects the current reference, the high-side switch turns off. During overcurrent conditions, such as when the sensing resistor is shorted, or an open circuit occurs in the feedback-filter RC network that drives FB low, the error amplifier responds by driving the COMP pin high, increasing the switch current. The error amplifier output is clamped internally. This clamp functions as a switch-current limit. This current limit is fixed at 3.1 A typical in PWM dimming mode. In analog dimming mode with the PWM duty cycle >25%, this limit is also 3.1 A. If the PWM duty cycle is below 25%, this limit is halved to 1.5 A typical. Furthermore, if an output overcurrent condition occurs for more than the shutdown delay time, t_{SHUTDOWN_DELAY}, the device shuts down and latches off to protect the LED from overcurrent damage.