As shown in Figure 2-1 and Figure 2-2, input current increases dramatically when input voltage drops. As a result, a much lower input voltage than expected draws much larger input current. This can also trigger unexpected overcurrent protection in the LED driver even though the LED driver can set enough OCP limit threshold.

VIN OCP current limit is to protect system from critical system hazard (for example, inductor short, switching MOSFET short). This triggers the device to shut-down all the LED channels and enter into fault recovery state. If the voltage across RISENSE resistor rises above 220mV during normal operation of the LP8866(S)-Q1 device, IC stops switching and LED outputs are turned off, and the device enters fault recovery mode and then attempt to restart 100ms after fault occurs. The VINOCP_STATUS fault bit are set in the SUPPLY_FAULT_STATUS register, and the INT pin is triggered

Therefore, if the system is not stable and the actual input voltage becomes much lower, designers must take care of unexpected overcurrent condition. This means inductor saturation current must be bigger and the OCP triggering point must be bigger which leads to less precise protection features due to system challenges.