8.3.2 Open LED Protection

Open LED protection circuitry prevents device damage as the result of white LED disconnection. The TPS61165 monitors the voltage at the SW pin and FB pin during each switching cycle. The circuitry turns off the switch FET and shuts down the device when both of the following conditions persist for 8 switching clock cycles: (1) the SW voltage exceeds the V_OVP threshold, and (2) the FB voltage is less than half of regulation voltage. As a result, the output voltage falls to the level of the input supply. The device remains in shutdown mode until it is enabled by toggling the CTRL pin. The product of the number of external series LEDs and the maximum forward voltage of each LED plus the 200-mV reference voltage does not exceed the 38-V minimum OVP threshold (N_LEDS × V_LED(MAX)) + 200 mV ≤ 38 V.