LDPC decoder, operating method of LDPC decoder, and semiconductor memory system

A Low Density Parity Check (LDPC) decoder comprising:

• a syndrome checker configured to assign each symbol of a codeword as a variable node value for each of a plurality of variable nodes and perform syndrome checking on each check node based on a parity check matrix;
• a flipping function calculator configured to calculate flipping function values of the variable nodes based on syndrome values of check nodes and a flipping function;
• a flipping function threshold value determiner configured to divide the flipping function values into a plurality of groups, and determine a flipping function threshold value based on a group maximum value of a group among the groups;
• and
• a variable node flipper configured to selectively flip a variable node value based on a comparison result of a flipping function value of corresponding variable node and the flipping function threshold value,
• wherein the flipping function threshold value determiner is configured to:
• select a group having a group maximum value of less than 0 by sequentially searching the plurality of groups;
• and
• determine a flipping function threshold value based on the group maximum value of the selected group.

A semiconductor memory system comprising:

• a semiconductor memory device;
• and
• a memory controller including a Low Density Parity Check (LDPC) decoder configured to perform error correction decoding on data read from the semiconductor memory device,
• wherein the LDPC decoder is configured to:
• assign each symbol of a codeword as a variable node value for each of a plurality of variable nodes;
• perform syndrome checking on each check node based on a parity check matrix;
• calculate flipping function values of the variable nodes based on syndrome values of check nodes and a flipping function;
• divide the flipping function values into a plurality of groups;
• determine a flipping function threshold value based on a group maximum value of a group among the groups and a look-up table;
• and
• selectively flip a variable node value based on a comparison result of a flipping function value of corresponding variable node and the determined flipping function threshold value,
• wherein the flipping function threshold value is determined by selecting a group having a group maximum value of less than 0 by sequentially searching the groups, and determining a flipping function threshold value based on the group maximum value of the selected group.