The TPS256x responds to overcurrent conditions by limiting the output current per channel to I_OS. 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 when the device is powered-up or enabled. The output voltage is held near zero potential with respect to ground and the TPS256x ramps the output current to I_OS. The TPS256x devices will 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 8-2). The current-sense amplifier is overdriven during this time and momentarily disables the internal current-limit MOSFET. The current-sense amplifier recovers and ramps the output current to I_OS. Similar to the previous case, the TPS256x will limit the current to I_OS until the overload condition is removed or the device begins to thermal cycle.

The TPS256x thermal cycles if an overload condition is present long enough to activate thermal limiting in any of the above cases. The device turns off when the junction temperature exceeds 135°C (min) while in current limit. The device remains off until the junction temperature cools 20°C (typ) and then restarts. The TPS256x cycles on/off until the overload is removed (see Figure 7-4).