The present invention relates generally to integrated circuit fuses and more particularly to circuits for programming and sensing the state of electrically programmable fuses.
Integrated circuits may often advantageously use permanent storage for holding information such as chip identification, redundancy placement, and calibration for trimming resistors, capacitors, other analog circuit components. Permanent storage that is reliable and economical is desirable.
Advantages of electrical fuses (efuses) for permanent storage in integrated circuits have been previously described, for example, in U.S. Pat. No. 7,098,721. Electrical fuses do not require special manufacturing equipment, such as laser trimming equipment needed for laser-cut fuses. Electric fuses are permanent under high stress conditions that may cause volatility problems with other permanent storage such as EEPROM. Additionally, electrical fuses do not require specialized fabrication processes.
However, programming and sensing circuits must be advanced to better use electrical fuses. The sense circuit should not alter the programming of the fuse, and the programming of the fuse should be sensed reliably and quickly.