Refresh frequency-dependent system-level trimming of verify level offsets for non-volatile memory

A controller in communication with a memory apparatus including memory cells each connected to one of a plurality of word lines and disposed in strings and configured to retain a threshold voltage corresponding to one of a plurality of data states, the controller configured to:

• instruct the memory apparatus to apply verification pulses of a plurality of program verify voltages each associated with one of the plurality of data states to selected ones of the plurality of word lines to determine whether the memory cells connected thereto have the threshold voltage above each of the plurality of program verify voltages associated with the plurality of data states targeted for each of the memory cells during a program-verify portion of a program operation;
• and
• trim the plurality of program verify voltages for each of the plurality of data states for a grouping of the memory cells based on quantities of the memory cells having the threshold voltage crossing over between the plurality of data states in a plurality of crossovers in a verify level trimming process.

A method of operating a memory apparatus including memory cells each connected to one of a plurality of word lines and disposed in strings and configured to retain a threshold voltage corresponding to one of a plurality of data states, the method comprising the steps of:

• applying verification pulses of a plurality of program verify voltages each associated with one of the plurality of data states to selected ones of the plurality of word lines to determine whether the memory cells connected thereto have the threshold voltage above each of the plurality of program verify voltages associated with the plurality of data states targeted for each of the memory cells during a program-verify portion of a program operation;
• and
• trimming the plurality of program verify voltages for each of the plurality of data states for a grouping of the memory cells based on quantities of the memory cells having the threshold voltage crossing over between the plurality of data states in a plurality of crossovers in a verify level trimming process.