Method and system for reducing soft-writing in a multi-level flash memory

A multilevel flash memory comprising:

• a memory cell configured to store a range of values;
• a first and second reference cells coupled to the memory cell and configured to receive a first and a second voltage during a read operation;
• and
• a current comparison circuit coupled to the first and second reference cells and to the memory cell and configured to compare current flow through the memory cell with current flow through the first and second reference cells, and to determine whether the memory cell holds a first range of values while the first reference cell receives the first voltage, and if the memory cell does not hold the first range of values, to determine whether the memory cell holds a second range of values while the second reference cell receives the second voltage, thereby reducing soft-writing during the read operation.

A method for reducing soft-writing in a multilevel flash memory during a read operation comprising:

• applying a first voltage to a first reference cell in the multilevel flash memory;
• determining, after applying the first voltage, whether a memory cell coupled to the first reference cell holds a first range of values;
• and
• if the memory cell does not hold the first range of values, then applying a second voltage to a second reference cell coupled to the memory cell.

A multilevel flash memory comprising:

• a memory cell configured to receive a first and a second voltage;
• a first and second reference cells coupled to the memory cell;
• and
• a current comparison circuit coupled to the first and second reference cells and to the memory cell and configured to compare current flow through the memory cell with current flow through the first and second reference cells during a read operation, and to determine whether the memory cell holds a first range of values while the memory cell receives the first voltage, and if the memory cell does not hold the first range of values, to determine whether the memory cell holds a second range of values while the memory cell receives the second voltage, thereby reducing soft-writing during the read operation.