Optimized Built-In Self-Repair for Multiple Memories

A new built-in self-repair (BISR) scheme is proposed for multiple embedded memories to find optimum point of the performance of BISR for multiple embedded memories. All memories are concurrently tested by the small dedicated built-in self-test to figure out the faulty memories, the number of faults, and irreparability. After all memories are tested, only faulty memories are serially tested and repaired by the shared built-in redundancy analysis according to the sizes of memories in descending order. Thus, the fast test and repair are performed with low area overhead. To accomplish an optimal repair rate and a fast analysis speed, an exhaustive search for all combinations of spare rows and columns is proposed based on the optimized fault collection. Experimental results show that the proposed BISR has the optimal repair rate because of the exhaustive search. The performance of the proposed BISR is located in the optimum point between the test and repair time, and the area overhead. For example, the proposed BISR requires 49.6% of the area and 1.3 times of the test and repair time in comparison with parallel BISR scheme for four memories (one 128 K, two 256 K, and one 512 K memories). Furthermore, the more there are memories, the more superior performance in terms of the test and repair time, and the area overhead is shown.