The TPS6128xD/E enters the fault state under any of the followings conditions:

• The output voltage fails to achieve the required level during a start-up phase.
• The output voltage falls out of regulation (in pre-charge mode).
• The device has entered thermal shutdown.

Once a fault is triggered, the regulator stops operating and disconnects the load. After waiting 1ms, the device attempts to restart. The TPS61280D device can be configured to signal a fault condition by pulling the open-drain GPIO pin (nFAULT) low for a short period of time. The nFAULT output provides a falling edge triggered interrupt signal to the host. To ensure proper operation, the GPIO port needs to be pull high quick enough, that is, faster than ca. 200ns. To do so, it is recommended to use a GPIO pull-up resistor in the range of 1kΩ to 10kΩ.

The TPS6128xD/E (simple logic I/F version) device only provide a power-good output (PG) for signaling the system when the regulator has successfully completed start-up and no faults have occurred. Power-good also functions as an early warning flag for excessive die temperature and overload conditions.

• PG is asserted high when the start-up sequence is successfully completed.
• PG is pulled low when the output voltage falls approximately 10% below its regulation level or the die temperature exceeds 115°C. PG is re-asserted high when the device cools below ca. 100°C.
• Any fault condition causes PG to be de-asserted.
• PG is pulled high when the device is operating in forced pass-through mode (that is, nBYP = L).
• PG is pulled high when the device is in shutdown mode.