Preferred Fill: A Scalable Method to Reduce Capture Power for Scan Based Designs

When the response to a test vector is captured by state elements in scan based tests, the switching activity of the circuit may be large resulting in abnormal power dissipation and supply current demand. High supply current may cause excessive supply voltage drops leading to larger gate delays which may cause good chips to fail tests. This paper presents a scalable approach called Preferred Fill to reduce average and peak power dissipation during capture cycles of launch off capture delay fault tests. Experimental results presented for benchmark and industrial circuits demonstrate the effectiveness of the proposed method