Controller and operating method thereof

An operating method of a controller controlling a memory device comprising a plurality of multi-level cell memory blocks, the operating method comprising:

• controlling the memory device to perform a read operation on a target logical page using some of a plurality of read voltages in a selected read voltage set of a plurality of read voltage sets stored in a memory of the controller, each of the read voltage sets having multiple read voltages for reading the multi-level cell memory blocks;
• determining whether the read operation is successful, by performing error detection and correction on data output from the memory device by the read operation;
• and
• updating the selected read voltage set with the read voltages used in the read operation when it is successful and estimated values of unused read voltages of the selected read voltage set, the estimated values being determined based on the used read voltages.

A memory system comprising:

• a memory device including a plurality of memory blocks;
• and
• a controller configured to:
• control the memory device to perform a read operation on a target logical page using select read voltages in a target read voltage set including the select read voltages and remaining read voltages;
• determine whether the read operation is successful;
• when it is determined that the read operation was successful, change a value of each of the remaining read voltages, based on a difference between previous and current values of each of the select read voltages;
• and
• update the target read voltage set such that the select read voltages have the current values and the remaining read voltages have changed values.