Operation of a non-volatile memory array
View Patent ↗A cache programming operation which requires 2 SRAMs (one for the user and one for the array) may be combined with a multi-level cell (MLC) programming operation which also requires 2 SRAMs (one for caching the data and one for verifying the data), using only a total of two SRAMs (or buffers). One of the buffers (User SRAM) receives and stores user data. The other of the two buffers (Cache SRAM) may perform a caching function as well as a verify function. In this manner, if a program operation fails, the user can have its original data back so that he can try to reprogram it to a different place (address).
1. A non-volatile memory (“NVM”) device comprising a first buffer adapted to receive data from an interface;
a second buffer adapted to receive data derived from data in said first buffer; and
control logic adapted to program an NVM array using data in said second buffer, wherein programming of the NVM array includes modifying data in said second buffer during a first phase of programming and refreshing data in said second buffer with at least some data from said first buffer prior to a second phase of programming.
2. The device according to claim 1 , wherein said first buffer is adapted to receive data from the external interface while said control logic is engaged in a second phase of programming.
3. The device according to claim 1 , wherein said first buffer is comprised of SRAM.
4. The device according to claim 1 , wherein said second buffer is comprised of SRAM.
5. The device according to claim 1 , wherein, as a part of the first phase of programming, said control logic is adapted to initiate a cycle of programming pulses followed by program verify operations.
6. The device according to claim 5 , wherein said control logic is adapted to terminate a first phase of programming once NVM cells in the NVM array reach a first given threshold voltage.
7. The device according to claim 6 , wherein said control logic is adapted to initiate a second phase of programming in order to raise the threshold voltage of NVM cells in the NVM array to a second given threshold voltage greater than the first given threshold voltage.
8. The device according to claim 1 , wherein said control logic is adapted, in the event the first phase programming fails, to initiate another first phase programming session by refreshing the said second buffer with data derived from data in said first buffer and programming a new NVM array address.
9. The device according to claim 1 , wherein said control logic is further adapted to scramble data being written to said second buffer from said first buffer.
10. The device of claim 1 , wherein the NVM cells are selected from the group consisting of floating gate (FG) cells and charge trapping type cells.
11. The device of claim 1 , wherein the NVM array is a flash memory.
12. A method of programming a non-volatile memory (“NVM”) device comprising:
placing data in a first buffer;
placing data in a second buffer derived from data in the first buffer; and
programming an NVM array using data in said second buffer, wherein programming of the NVM array includes modifying data in said second buffer during a first phase of programming and refreshing data in said second buffer with at least some data from said first buffer prior to a second phase of programming.
13. The method according to claim 12 , further including receiving data from an external interface while during second phase of programming.
14. The method according to claim 12 , wherein the first phase programming includes a cycle of programming pulses followed by program verify operations.
15. The method according to claim 14 , including terminating a first phase of programming once NVM cells in the NVM array reach a first given threshold voltage.
16. The method according to claim 15 , including initiating a second phase of programming in order to raise the threshold voltage of NVM cells in the NVM array to a second given threshold voltage greater than the first given threshold voltage.
17. The method according to claim 12 , wherein said control logic is adapted, in the event the first phase programming fails, to initiate another first phase programming session by refreshing the said second buffer with data derived from data in said first buffer and programming a new NVM array address.