- Polyfuse
A Polyfuse is a one-time-programmable memory component used in
semiconductor circuits for storing unique data like chip identification numbers or memory repair data. Polyfuses were developed as a replacement oflaser fuses. Initially, the flexibility of electrical programming was the main driver. In addition to adding flexibility, modern polyfuses are much smaller than laser fuses, since they do not require as much distance between the devices. Laser fuses need this large distance since a lot of debris is generated by blowing the fuses up with a laser. This debris can unprogram nearby programmed devices.History
The first polyfuses consisted of a polysilicon line, which was programmed by applying a high (10V-15V)
voltage across the device. The resultant current physically alters the device and results in an increase inelectrical resistance . This change in resistance can be detected and registered as a logical one. An unprogrammed polyfuse would be registered as a logical zero. These early devices had severe drawbacks like a high programming voltage and unreliability of the programmed devices.Modern polyfuses
Modern polyfuses consist of a siliced
polysilicon line, which is also programmed by applying a voltage across the device. Again, the resultant current physically alters the device and results in an increase in resistance. Thesilicide layer covering the polysilicon line reduces its resistance (before programming), allowing the use of much lower programming voltages (1.8V-3.3V). Polyfuses have been shown to reliably store programmed data and can be programmed at high speed. Programming speeds of 100ns has been reported.ee also
*
Programmable read-only memory
*Resettable fuse
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