JAJSJM2B July 2022 – April 2024 TPS929240-Q1
PRODUCTION DATA
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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.