7.3.3 Internal Foldback Current Limit

The TLV743P device has an internal foldback current limit that protects the regulator during fault conditions. The current allowed through the device is reduced as the output voltage falls. When the output is shorted, the LDO supplies a typical current of 150 mA. The output voltage is not regulated when the device is in current limit. In this condition, the output voltage is the product of the regulated current and the load resistance. When the device output is shorted, the PMOS pass transistor dissipates power [(V_IN – V_OUT) × I_OS] until thermal shutdown is triggered and the device turns off. After the device cools down, the internal thermal shutdown circuit turns the device back on. If the fault condition continues, the device cycles between current limit and thermal shutdown. See Thermal Information for more details.

The foldback current limit circuit limits the current allowed through the device to current levels lower than the minimum current limit at nominal V_OUT current limit (I_LIM) during startup. See Figure 18 to Figure 20 for typical foldback current limit values. If the output is loaded by a constant-current load during startup, or if the output voltage is negative when the device is enabled, then the required load current by the load may exceed the foldback current limit and the device may not rise to the full output voltage. For constant current loads, disable the output load until the TLV743P has risen to the nominal output voltage.

The TLV743P PMOS pass element has an intrinsic body diode that conducts current when the voltage at the OUT pin exceeds the voltage at the IN pin. Do not force the output voltage to exceed the input voltage because excessively high current may flow through the body diode.