8.3.10.2 LED Short Protection

When the LED load is shorted, the FB voltage is higher than V_REF, and the internal COMP voltage is driven low and clamped, and the high-side MOSFET is commanded on for a minimum on-time each cycle. In this condition, if the output voltage is too low, the inductor current may not be able to balance in a cycle, causing current runaway. Finally, the inductor current is clamped at the low-side MOSFET sourcing-current limit, which is much higher than target LED current. If the FB voltage is higher than the OCP threshold, which is 250 mV typical in analog dimming mode, or 120 mV typical in PWM dimming mode, the shutdown delay counter (TPS54200) or auto-retry wait counter (TPS54201) is triggered. For the TPS54200 device, once the shutdown delay time t_{SHUTDOWN_DELAY} expires, the device shuts down and latches off. Both FETs are kept off. This is a latched shutdown. The device can be reset by recycling VIN. For the TPS54201 device, once the auto-retry wait time t_{HIC_WAIT} expires, the device shuts down and starts auto-retry timer t_{HIC_OC}. During the shutdown period, both FETs are kept off. Once the auto-retry timer expires, the TPS54201 device restarts again. If the failure still exists, the TPS54201 device repeats the foregoing shutdown-and-restart process.