The TPS22950 responds to overcurrent conditions by limiting its output current to the I_LIM level shown in the figure below.

Figure 9-1 Output Current Limit for Short-Circuit Protection (t_LIM)

When an overcurrent condition is detected, the device maintains a constant output current and reduces the output voltage accordingly. Two possible overload conditions can occur.

The first condition is when a short circuit or partial short circuit is present on the output and the ON pin is toggled high, turning the device on. The output voltage is held near zero potential with respect to ground and the TPS22950 ramps the output current to I_LIM. The TPS22950 device limits the current to I_LIM until the overload condition is removed or the internal junction temperature of the device reaches thermal shutdown and the device turns itself off. The device remains off until the junction temperature has lowered to TSD_HYS, and the device turns itself back on. This action cycles until the overload condition is removed.

The second condition is when a short circuit, partial short circuit, or transient overload occurs after the device has been fully powered on. The device responds to the overcurrent condition within time t_LIM (see figure below), and before this time the current is able to exceed I_LIM. In the case of a fast transient, the current-sense amplifier is over-driven and momentarily disables the internal power FET. The current-sense amplifier recovers and limits the output current to I_LIM. Similar to the previous case, the TPS22950 limits the current to I_LIM until the overload condition is removed or the internal junction temperature of the device reaches thermal shutdown and begins thermally cycling on and off.

Figure 9-2 Transient Current Limit Waveform