US Patent 7420791 Fault signature system for power management integrated circuits

A power management IC including a dual purpose pin, a fault detection system, and a fault signature system. The dual purpose pin performs a power management function during normal operation (e.g., a soft start pin coupled to an external capacitor, a set pin coupled to an external resistor, a frequency set pin coupled to a resistor-capacitor combination, etc.). The fault detection system senses any of multiple fault conditions and provides a corresponding fault indicator signal, each indicating a corresponding fault condition. The fault signature system generates a selected fault signature signal on the dual purpose pin, where each fault signature signal has a characteristic indicative of a corresponding fault condition. Thus, an existing pin on the IC is re-used to indicate the fault condition. The fault signature signal may be a unique voltage level, a unique charging rate, a unique frequency signal, or any a combination thereof.