Simultaneous reduction of dynamic and static power in scan structures

Power dissipation during test is a major challenge in testing integrated circuits. Dynamic power has been the dominant part of power dissipation in CMOS circuits, however, in future technologies the static portion of power dissipation will outreach the dynamic portion. This paper proposes an efficient technique to reduce both dynamic and static power dissipation in scan structures. Scan cell outputs which are not on the critical path(s) are multiplexed to fixed values during scan mode. These constant values and primary inputs are selected such that the transitions occurring on nonmultiplexed scan cells are suppressed and the leakage current during scan mode is decreased. A method for finding these vectors is also proposed. The effectiveness of this technique is proved by experiments performed on ISCAS89 benchmark circuits.