The TPS929240-Q1 integrates LED open-circuit diagnostics to allow users to monitor LED status real time. The device monitors voltage difference between SUPPLY and OUTXn to judge if there is any open-circuit failure. The SUPPLY voltage is also monitored in parallel with programmable threshold to determine if supply voltage is high enough for open-circuit diagnostics.

The open-circuit monitor is only effective during PWM-ON state with programmable minimal pulse width greater than t_(BLANK) + t_{(OPEN_deg)}. The t_(BLANK) is programmed by register BLANK. If PWM on-time is less than t_(BLANK) + t_{(OPEN_deg)}, the device does not report any open-circuit fault. When the device supply voltage V_(SUPPLY) is below the threshold V_(LOWSUPTH) set by register LOWSUPTH, the LED open-circuit is not detected nor reported.

When the voltage difference V_(SUPPLY) – V_(OUTXn) is below threshold V_{(OPEN_th_rising)} with duration longer than t_(BLANK) + t_{(OPEN_deg)}, and the device supply voltage V_(SUPPLY) is above the threshold V_(LOWSUPTH) set by register LOWSUPTH, the TPS929240-Q1 pulls the ERR pin down with one pulsed current sink for 50 μs to report fault and set flag registers including FLAG_OPENOUTXn, FLAG_OUT and FLAG_ERR to 1. In NORMAL state, the device does not take any actions in response the LED open-circuit fault and waits for the master controller to determine the protection behavior.

The fault is latched in flag registers. When the voltage difference V_(SUPPLY) – V_(OUTXn) rises above threshold V_{(OPEN_th_rising)} with duration longer than t_(BLANK) + t_{(OPEN_deg)}, or the device supply voltage V_(SUPPLY) is below the threshold V_(LOWSUPTH), the master controller must write 1 to CLRFAULT to clear FLAG_OPENOUTXn, FLAG_OUT and FLAG_ERR. The CLRFAULT bit automatically returns to 0.