8.3.3 Current Limiting (V_SC)

The TPS22948 responds to overcurrent conditions by limiting its output current to the ILIM level shown in Figure 6.

Figure 6. TPS22948 Current Limiting Behavior

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 TPS22948 ramps the output current to I_LIM. The TPS22948 device will limit 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 by TSD_HYS, and the device will turn itself back on. This will cycle 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 7), and before this time, the current is able to exceed I_LIM. In the case of a fast transient, the current-sense amplifier is overdriven 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 TPS22948 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 7. Transient Current Limit Waveform