Yield improvement through block budget optimization by using a transient pool of multi-level blocks

A method, comprising:

• programming and erasing data in a first set of blocks in an M bit per cell mode;
• programming and erasing data in a second set of blocks in an N bit per cell mode;
• transitioning blocks in the second set of blocks to the M bit per cell mode from the N bit per cell mode, where M<N;
• and
• maintaining a respective count of program-erase cycles for each block of the second set of blocks, the respective count of program-erase cycles is incremented by a first amount when data is programmed and erased in the block in the M bit per cell mode and by a second amount, which is greater than the first amount, when data is programmed and erased in the block in the N bit per cell mode.

An apparatus, comprising:

• a set of memory cells arranged in a plurality of blocks, the plurality of blocks comprising a first set of blocks and a second set of blocks;
• and
• a control circuit, the control circuit is configured to:
• store data in the first set of blocks in an M bit per cell mode;
• repeatedly transition blocks in the second set of blocks between storing data in the M bit per cell mode and storing data in an N bit per cell mode, where M<N;
• maintain a respective count of M bit per cell program-erase cycles of each block of the second set of blocks;
• maintain a respective count of N bit per cell program-erase cycles of each block of the second set of blocks;
• and
• keep the respective counts of M bit per cell program-erase cycles of the second set of blocks uniform within a first tolerance, and keep the respective counts of N bit per cell program-erase cycles of the second set of blocks uniform within a second tolerance, during the repeated transition of the blocks in the second set of blocks.