A simple design methodology for testable flash A/D converter output encoding

A Boolean matrix technique is presented for the design of easily tested digital-encoding circuits to follow a flash analog-to-digital converter. The digital encoding is performed using a form of Reed-Muller network. The Reed-Muller configuration is known to be easily tested, but the design of this type of network to implement arbitrary logic equations is very difficult. The author demonstrates that the unique structure of the comparator outputs in a flash converter permits the highly testable Reed-Muller network to be designed easily with arbitrary encoding. The testability implications are discussed and a design example is presented