The TPS25200 thermally protects itself by thermal cycling during an extended overcurrent condition. The device turns off when the junction temperature exceeds 135°C (typical) while in current limit. The device remains off until the junction temperature cools 20°C (typical) and then restarts. The TPS25200 cycles on/off until the overload is removed (see Figure 9-13 and Figure 9-16).

The TPS25200 responds to an overcurrent condition by limiting their output current to the I_OS levels shown in Figure 7-4. When an overcurrent condition is detected, the device maintains a constant output current and the output voltage is reduced accordingly. During an over current event, two possible overload conditions can occur.

The first condition is when a short circuit or partial short circuit is present when the device is powered-up or enabled. The output voltage is held near zero potential with respect to ground and the TPS25200 ramps the output current to I_OS. The TPS25200 devices limit the current to I_OS until the overload condition is removed or the device begins to thermal cycle.

The second condition is when a short circuit, partial short circuit, or transient overload occurs while the device is enabled and powered on. The device responds to the overcurrent condition within time t_IOS (see Figure 7-4). The current-sense amplifier is overdriven during this time and momentarily disables the internal current-limit MOSFET. The current-sense amplifier recovers and limits the output current to I_OS. Similar to the previous case, the TPS25200 limits the current to I_OS until the overload condition is removed or the device begins to thermal cycle.