7.3.5.1 Open-Circuit Detection

The TPS92613-Q1 device has LED open-circuit detection. The LED open-circuit detection monitors the output voltage when the current output is enabled. The LED open-circuit detection is only enabled when DIAGEN is HIGH. A short-to-battery fault is also detected and recognized as an LED open-circuit fault.

The TPS92613-Q1 monitors dropout-voltage differences between the IN and OUT pins when PWM is HIGH. The voltage difference V_(IN) – V_(OUT) is compared with the internal reference voltage V_{(OPEN_th_falling)} to detect an LED open-circuit incident. If V_(IN) – V_(OUT) falls below the V_{(OPEN_th_falling)} voltage longer than the deglitch time of t_{(OPEN_deg)}, the device asserts an open-circuit fault. Once an LED open-circuit failure is detected, the internal constant-current sink pulls down the FAULT pin voltage. During the deglitch time period, if V_(IN) – V_(OUT) rises above V_{(OPEN_th_rising)}, the deglitch timer is reset.

The TPS92613-Q1 keeps the current output enabled to retry after LED open-circuit fault is detected if the PWM input is HIGH; the device sources a small current I_(retry) from IN to OUT when PWM input is LOW. In either scenario, once the fault condition is removed, the device resumes normal operation and releases the FAULT pin.