Fuses in Silicon

I’m going to start this topic with the dictionary meaning of the term electrical Fuse.

A safety device consisting of mechanism that can interrupt a circuit when the current exceeds a particular amperage.

Literally, the idea of providing a fail-safe mechanism remains the same. What changes is the design and implementation.

Typically any circuit that is intended for tape-in/tape-out as a physical chip would ideally have this design. Chip-makers use fuses to make certain parts/the whole part of the silicon immutable. This sometimes referred as blowing the fuses or burning the fuses, on the chip.

There are several designs that can do this. The simplest design I can come up whilst I’m writing this, is a 1-bit register. Using an AND gate to connect output of the circuit you want to turn-off with our 1-bit Register(fuse), and sampling the output of the AND gate itself we can control the circuit’s existence. Throw in a Mux there, it can make wonders.

Don’t believe me, see for yourself: Strap-based multiplexing scheme Patented by Yean Kee Yong.

In short, there’s some data that sits in fuse’s RAM/ROM which will contain key feature information. This information can be pushed in the form of Fuse Data to various parts of the chip, to control its individual functions. Simply Put :On/Off/Bypass Switch.