TPS272C45 provides output short-circuit protection to ensure that the device prevents current flow in the event of a low impedance path to GND, removing the risk of damage or significant supply droop. The device is specified to protect against short-circuit events regardless of the state of the ILIM pins and or supply voltages up to 36V and across the entire opeprating temperature range -40 °C 125°C.

Figure 9-7 shows the behavior of the TPS272C45 when the device is enabled into an overload condition and then recovers to a normal load.

Figure 9-7 Enable into Short-Circuit Behavior

Due to the low impedance path, the output current rapidly increases until it hits the current limit threshold. Due to the response time of the current limiting circuit, the measured maximum current can temporarily exceed the I_CL value defined as I_{CL_ENPS}, before it settles to the current limit regulation value (I_CL).

In this state high power is dissipated in the FET, so eventually the internal thermal protection temperature for the FET is reached and the device safely shuts down. Then if LATCH pin is low the part waits t_RETRY amount of time and turns back on.

Figure 9-8 shows the behavior of the TPS272C45 when a short-circuit occurs when the device is in the on-state and already outputting current. When the internal pass FET is fully enabled, the current clamping settling time is slower so to ensure overshoot is limit, the device implements a fast trip turn-off at a high current threshold (approximately 40% higher than I_CL). When this fast trip threshold is hit, the device shuts off after a delay for a short period of time before quickly re-enabling and clamping the current to the regulation current limit level (I_CL) after a brief transient overshoot to the higher peak current level. The device then keeps the current clamped at the regulation current limit until the thermal shutdown temperature is hit and the device safely shuts off.

Figure 9-8 On-State Short-Circuit Behavior

Overload Behavior shows the behavior of the TPS272C45 when there is a small change in impedance that sends the load current above the I_CL threshold. The current rises to I_{CL_LIN} above the regulation level. Then the current limit regulation loop kicks in and the current drops to the I_CL value.

Figure 9-9 Overload Behavior

In all of these cases, the internal thermal shutdown is safe to hit repetitively. There is no device risk or lifetime reliability concerns from repeatedly hitting this thermal shutdown level.