Patent ID: 7084696

Claim:
An identification circuit for establishing and sensing of a fusible element used in on-chip identification of the chip's type comprising: a circuit establishing control signals for turning the identification circuit on and off for sensing with an initiating signal remains off during the personalization of the fusible element; dual paths energized by the control signals generated by the level setting circuit to energize one path through the fusible element to provide a state level and the other path through a reference path which provides a reference voltage level which is distinguishable from both the blown and unblown states of the fusible element wherein, the dual paths are each a series circuit that includes switching devices responsive to the control signals for making and breaking the reference paths and isolation devices in series with the switching devices to isolate them and other circuit chip elements from the fusible element while the fusible element is being personalized wherein, the isolation devices include two devices in series with the personalizing FET a first of which is responsive to the fusing source of potential to be biased conductive during the personalization step and a second of which is turned on during personalization to isolate the other circuits in the loop from the personalization process; differential sensing circuit for comparing the reference voltage level to the state level to provide a signal indicating the state of the fusible element; protection circuitry changing voltage levels on the dual paths and the differential sensing circuit to protect the circuit during an operation in which the state of the fusible element is set; and a fusible element personalization circuit to establish the state of the fusible element wherein, the personalization circuit includes a personalizing FET and a source of potential capable of fusing the fusible element arranged in series with the fusible element; and a NOR circuit controlling the personalization FET responsive to the presence or absence of a blow signal to establish the state of the fusible element.