8.3.1 Overcurrent Conditions

The TPS2553-Q1 device responds to overcurrent conditions by limiting the output current to the I_OS levels shown in Figure 22. When the device detects an overcurrent condition, 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 TPS2553-Q1 device ramps the output current to I_OS. The TPS2553-Q1 device will limit the current to I_OS until the overload condition is removed or the device begins to thermal cycle. The device will remain off until power is cycled or the device enable is toggled.

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 20). 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 TPS2553-Q1 device will limit the current to I_OS until the overload condition is removed or the device begins to thermal cycle.

The TPS2553-Q1 device thermal cycles if an overload condition is present long enough to activate thermal limiting in any of the previous cases. 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 10°C (typical) and then restarts. The TPS2553-Q1 device cycles on and off until the overload is removed (see Figure 5 and Figure 7).