The TPS1HC120-Q1 provides output short-circuit protection to ensure that the device will prevent current flow in the event of a low impedance path to GND, removing the risk of damage or significant supply droop. The device is guaranteed to protect against short-circuit events up to 28V supply.

Figure 7-4 shows the behavior of the TPS1HC120-Q1 when the device is enabled into a short-circuit.

Figure 7-4 Enable Into Permanent Short

Once the device is enabled, due to the low impedance path, the output current will rapidly increase until it hits the current limit threshold (I_CL). Due to the response time of the current limiting circuit, the measured maximum current may temporarily exceed the I_CL value defined as I_{CL_ENPS}, however, it will settle to the current limit regulation value. 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. After thermal shutdown,

• The device will retry after t_RETRY duration if the inrush period (t_INRUSH) has not expired. The inrush period starts from the EN rising edge.
• After the inrush period expires, output voltage (V_OUT) is sensed every time thermal shutdown is hit.
  • If V_OUT is less than 3V, as is the case for strong output short to ground, the device will be latched off until EN inputs toggle.
  • If V_OUT is higher than 3V, for example, for an overload scenario, the device will retry.

Figure 7-5 shows the behavior of the TPS1HC120-Q1 when a short-circuit occurs while the device is in the on-state and already delivering current. When the internal pass FET is fully enabled, the current limiting response time is slower. So to ensure that the current overshoot is limited, the device implements a fast trip at a level I_OVCR. When this fast trip threshold is hit, the device immediately shuts off for a short period of time before quickly re-enabling and clamping the current to I_CL level after a brief transient overshoot to the higher peak current (I_{CL_ENPS}) level. The device will then keep the current clamped at the regulation current limit until the thermal shutdown temperature is hit and the device will safely shut-off. Once thermal shutdown is hit, the device will latch off till the enable inputs toggle if the output voltage is less than 3V, and will retry if the output voltage is more than 3V.

Once the device re-enables due to enable input toggling, if the output short still exists, the scenario is identical to the enable into permanent short scenario.

Figure 7-5 On-State Short-Circuit Behavior

Figure 7-6 shows the behavior of the TPS1HC120-Q1 when there is a small change in impedance that sends the load current above the I_CL threshold. The current rises to I_{CL_LINPK} above the regulation level. Then the current limit regulation loop kicks in and the current drops to the I_CL value.

Figure 7-6 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.