LDO regulator with thermal shutdown system and method

An apparatus that regulates a regulation voltage across a load from an unregulated power supply, comprising:

• a means for regulating that selectively couples power from the unregulated power supply to the load in response to a control signal;
• a means for coupling unregulated power that selectively couples power from the unregulated power supply to an internal power supply when activated by an over-temperature signal;
• a means for sensing that produces an over-temperature signal when all over-temperature condition is detected;
• a means for coupling regulated power that couples power from the regulation voltage to the internal power supply when the internal power supply is less than the regulation voltage;
• a means for providing feedback that provides a feedback voltage from the regulation voltage, wherein the feedback voltage is at least a portion of the regulation voltage;
• and
• a means for controlling that provides the control signal in response to the feedback voltage and a reference voltage such that the regulation voltage across the load is regulated by the means for controlling and the means for regulating when the over-temperature signal is deactivated, wherein the means for controlling operates from the internal power supply.

A method for regulating a regulation voltage across a load from an unregulated power supply that has an associated unregulated power supply voltage, comprising:

• controlling a series regulation circuit with a control signal;
• coupling power from the unregulated power supply to the load in response to the control signal;
• coupling power from the series regulation circuit to an internal power supply that has a corresponding internal power supply voltage when the internal power supply voltage is lower than the regulation voltage;
• producing a feedback voltage that corresponds to at least a portion of the load regulation voltage;
• producing a first and second reference voltage with a reference circuit;
• producing the control signal with an error amplifier circuit in response to the feedback voltage to the first reference voltage;
• sensing an over-temperature condition with a temperature sensor circuit that utilizes the second reference voltage;
• producing the over-temperature signal in response to the over-temperature condition;
• coupling the unregulated power supply to an internal power supply when activated by the over-temperature sensor signal;
• disabling the series regulation circuit after coupling the unregulated power supply to the internal power supply;
• and
• operating the error amplifier circuit and the reference circuit from the internal power supply such that the regulation voltage has improved power supply rejection during regulation.