Flash channel with selective decoder likelihood dampening

A method of selectively dampening decoder inputs in a flash channel, comprising:

• generating a plurality of likelihood value sets for a codeword read from a flash memory;
• decoding the plurality of likelihood value sets and calculating a syndrome for each of the plurality of likelihood value sets that is decoded;
• selecting at least one dampening candidate from among the likelihood value sets for which the decoding failed;
• dampening at least a portion of the likelihood value set for the at least one dampening candidate to yield at least one dampened likelihood value set;
• and
• decoding the at least one dampened likelihood value set.

A flash memory system comprising:

• a flash memory operable to store a codeword;
• a read controller operable to read data representing the codeword from the flash memory;
• a likelihood generator operable to generate a plurality of likelihood value sets for the data;
• a decoder operable to decode the plurality of likelihood value sets and to calculate a syndrome for each of the plurality of likelihood value sets that is decoded;
• and
• a selective dampening controller operable to select at least one dampening candidate from among the likelihood value sets for which the decoding failed, to dampen at least a portion of the likelihood value set for the at least one dampening candidate to yield at least one dampened likelihood value set, and to provide the at least one dampened likelihood value set to the decoder for decoding.