Automated synthesis of phase shifters for built-in self-test applications

This paper presents novel systematic design techniques for the automated register transfer level synthesis of phase shifters-circuits used to remove effects of structural dependencies featured by pseudorandom test pattern generators driving parallel scan chains. Using a concept of linear feedback shift register (LFSR) duality this paper relates the logical states of LFSRs and circuits spacing their inputs to each of the output channels. Consequently, the method generates a phase-shifter network satisfying criteria of channel separation and circuit complexity by taking advantage of simple logic simulation of the LFSRs. It is shown that it is possible to synthesize in a time-efficient manner very large and fast phase shifters for built-in self-test applications with guaranteed minimum phaseshifts between scan chains, and very low delay and area of virtually one two-way XOR gate/channel.