As described in Section 2, actual input voltage on LED driver will be much smaller if the input voltage is dropped due to the losses across long PCB pattern, power cable, ideal diode, high-side switch and so on. This is worse when two LED drivers are used as in this system example. This unexpected low input voltage on the LED driver can go below 3V due to system challenges and trigger VIN UVLO protection even though the LED driver can support up to 3V input voltage.

The undervoltage threshold is programmable through external resistor divider on the UVLO pin. If the UVLO pin voltage falls below the UVLO falling level (0.787V typical) during normal operation of the LP8866(S)-Q1 device, the IC stops switching and LED outputs are turned off and the device enters STANDBY mode. The VINUVLO_STATUS bit is also set in the SUPPLY_FAULT_STATUS register, and the INT pin is triggered. When the UVLO voltage rises above the rising threshold level, the LP8866(S)-Q1 exits STANDBY and begins the start up sequence.

Therefore, if the system is not stable under cranking condition which leads VIN drop below than 3V, LED driver cannot light up as the expected scenario. The UVLO protection setting must have much bigger margin to mitigate the risk, but the UVLO protection cannot achieve expected precise protection which is not efficient.