Memory built-in self test error correcting code (MBIST ECC) for low voltage memories

A circuit comprising:

• a memory;
• a built-in self test input-output interface (BIO);
• a built-in self test (BIST) engine which is configured to interface with the BIO to run a plurality of patterns in a sliding window of the memory for a low voltage corner repair mode;
• a scratchpad module which is configured to store failures for the plurality of patterns of the sliding window in a plurality of scratchpad registers,
• wherein the scratchpad module is further configured to compare a row of an incoming cell failure with a row of previously stored failures in the plurality of scratchpad registers to (i) determine whether the incoming failure is a single cell failure for a single wordline and (ii) determine whether the incoming failure is a multi-cell failure for the single wordline;
• and
• a repair module configured to selectively repair both the single cell failure and the multi-cell failure, wherein the repair module is configured to (i) in response to the scratchpad module determining that the incoming cell failure is the multi-cell failure, repair the multi-cell failure and (ii) in response to the scratchpad module determining that the incoming cell failure is the single cell failure, leave the single cell failure unrepaired,
• wherein the BIST engine is configured to complete repair of multi-cell failures in the memory and clear the plurality of scratchpad registers to leave any single cell failures in the memory unrepaired.

A method of operating a circuit configured to repair both single cell failures and multi-cell failures of a memory, the method comprising:

• programming a sliding window for the memory, wherein the sliding window corresponds to a portion of the memory and a size of the sliding window corresponds to a size of the portion of the memory;
• running a memory built-in self test (MBIST) for a plurality of patterns in the sliding window for the memory during a low voltage corner repair mode;
• storing all cell failures for the plurality of patterns in the sliding window for the memory in a plurality of scratchpad registers;
• comparing a row of the incoming cell failure with a row of previously stored failures in the plurality of scratchpad registers
• determining whether an incoming cell failure of the cell failures is a single cell failure for a single wordline and determining whether the incoming cell failure is a multi-cell failure for the single wordline;
• repairing the multi-cell failure by using redundant rows and columns in response to determining that the incoming cell failure is the multi-cell failure;
• in response to determining that the incoming cell failure is the single cell failure, leaving the single cell failure unrepaired;
• dynamically reducing the size of the sliding window in response to each of the plurality of scratchpad registers being full;
• and
• completing repair of multi-cell failures in the memory and clearing the plurality of scratchpad registers to leave any single cell failures in the memory unrepaired.