System and method for pre-soft-decoding tracking for nand flash memories

A flash memory system comprising:

• a flash memory;
• and
• a circuit for performing operations on the flash memory, the circuit being configured to:
• obtain a first soft read sample by performing a first read operation on a location of the flash memory with a first reference voltage;
• determine a second reference voltage based on the first soft read sample;
• obtain a second soft read sample by performing a second read operation on the location of the flash memory with the second reference voltage;
• generate soft information based on the first and second soft read samples;
• and
• decode result of a third read operation on the location of the flash memory based on the soft information.

A method for performing operations on a flash memory, the method comprising:

• obtaining one or more soft read samples;
• estimating reference voltages from the one or more soft read samples;
• and
• performing read operations on locations of the flash memory with the estimated reference voltages,
• wherein estimating reference voltages comprises:
• determining a sampling range based on a first one of the one more soft read samples;
• determining a second reference voltage from within the sampling range;
• and
• generating a histogram based on the one or more soft read samples, wherein
• determining the sampling range comprises:
• updating the histogram based on the first soft read sample, and
• determining the sampling range based on the histogram.