The TPS929121-Q1 has internal analog comparators to monitor all channel outputs with respect to a fixed threshold. If the device has detected channel voltage below threshold, it sets FLAG_SHORTCHx accordingly. The FLAG_OUT and FLAG_ERR are set as well. Writing 1 to CLR_FAULT register is able to clear the fault flag registers.

The short-circuit detection is only enabled during PWM-ON state with programmable minimal pulse width of T_(ODPW) + T_{(SHORT_deg)}. The T_(ODPW) is programmable by register CONF_ODPW. If PWM on-time is less than T_(ODPW) + T_{(SHORT_deg)}, the device can not report any short-circuit fault. When the voltage V_(OUTx) is below threshold V_{(SG_th_rising)} with duration longer than deglitch timer length of T_(ODPW) + T_{(SHORT_deg)}, the device pulls ERR pin down with pulsed current sink for 50 µs to report fault and set flag registers including FLAG_SHORTCHx, FLAG_OUT and FLAG_ERR. In normal state, the device does not take any actions in response the LED short-circuit fault and waits for the master controller to detect need for protection behavior. The fault is latched in flag registers. The master controller must write 1 to register CLR_FAULT to reset fault flags if the LED short-circuit fault is removed.

Possible user case:

1. Supply voltage dip below threshold, triggering false single led short-circuit fault
2. LED short to ground and recover
3. LED single LED short and recover
4. Dutycycle too short to detect
5. Extra capacitance caused false short-circuit