Hybrid test application in hybrid delay scan design

The hybrid delay scan design in which some flip flops (FFs) are controlled as skewed-load FFs and the others are controlled as broad-side FFs was proposed. Noticing that the hybrid delay scan design potentially has a capability of two test application modes: one is the broad-side test mode, and the other is the hybrid test mode, we present a hybrid test application of the two test modes in the hybrid delay scan design. In addition, we also address a way of skewed-load FF selection based on propagation dominance of FFs in order to take advantage of the hybrid test application. Experimental results for ITC´99 benchmark circuits show that the proposed hybrid scan design with the hybrid test application can achieve higher fault coverage than the previous hybrid scan design.