Resistive change element arrays with in situ initialization
A high-speed memory circuit architecture for arrays of resistive change elements is disclosed. An array of resistive change elements is organized into rows and columns, with each column serviced by a word line and each row serviced by two bit lines. Each row of resistive change elements includes a pair of reference elements and a sense amplifier. The reference elements are resistive components with electrical resistance values between the resistance corresponding to a SET condition and the resistance corresponding to a RESET condition within the resistive change elements being used in the array. A high speed READ operation is performed by discharging one of a row's bit lines through a resistive change element selected by a word line and simultaneously discharging the other of the row's bit lines through of the reference elements and comparing the rate of discharge on the two lines using the row's sense amplifier. Storage state data are transmitted to an output data bus as high speed synchronized data pulses. High speed data is received from an external synchronized data bus and stored by a PROGRAM operation within resistive change elements in a memory array configuration.
1. A resistive change element memory array, comprising:
a plurality of word lines;
a plurality of bit lines;
a plurality of select lines;
a plurality of initialization driver circuits;
a plurality of memory cells, said memory cells comprising:
a resistive change element having a first terminal and a second terminal, said first terminal in electrical communication with a select line and an initialization driver circuit, wherein said resistive change element is capable of being switched between at least two non-volatile resistance values with a first resistance value corresponding to a first resistive state and a second resistance value corresponding to a second resistive state;
a selection device responsive to a control signal on a word line, said selection device selectively providing a conductive path between a bit line and said second terminal of said resistive change element;
wherein said plurality of initialization driver circuits are capable of applying initialization stimuli to said resistive change elements within said plurality of memory cells;
wherein said initialization stimuli enables operation of said plurality of memory cells within at least two informational states.
2. The resistive change element array of claim 1 wherein said initialization stimuli enables bipolar operation of said plurality of memory cells.
3. The resistive change element array of claim 1 wherein the at least two informational states are verifiable using a READ operation.
4. The resistive change element array of claim 1 wherein said first resistive state is lower than said second resistive state.
5. The resistive change element array of claim 1 wherein said plurality of select lines and said plurality of initialization driver circuits are electrically connected to said resistive change elements through a plurality of switching elements.
6. The resistive change element array of claim 5 wherein said plurality of switching elements selected provides electrical communication between said initialization driver circuits and said plurality of memory cells during an initialization operation and between said plurality of select lines and said plurality of memory cells during normal array operation.
7. The resistive change element array of claim 1 wherein said plurality of select lines and said plurality of initialization driver circuits are electrically connected directly to said resistive change elements.
8. The resistive change element array of claim 7 wherein said plurality of initialization driver circuits are capable of being tri-stated.
9. The resistive change element array of claim 8 said plurality of initialization driver circuits are tri-stated during normal array operation.
10. The resistive change element array of claim 1 wherein said plurality of initialization driver circuits are responsive to an initialization driver controller.
11. The resistive change element array of claim 10 wherein said initialization driver controller is an on-chip programmable circuit.
12. The resistive change element array of claim 10 wherein said initialization driver controller coordinates at least one of the timing, the amplitude, the pulse width, the number of pulses, and the connectivity of said plurality of initialization driver circuits.
13. The resistive change element array of claim 1 wherein said initialization driver circuits are capable of providing significantly higher voltages and currents during an initialization operation as compared to those required for read and programming operations with said array.
14. The resistive change element array of claim 13 wherein a programming operation of a memory cell within said array requires an electrical stimulus on the order of 2.5 Volts and an initialization operation on said memory cell requires an electrical stimulus on the order of 3.5 Volts.
15. The resistive change element array of claim 13 wherein elements used to drive electrical stimuli onto said plurality of word lines, said plurality of bit lines, and said plurality of select lines are protected from said higher voltages and currents during an initialization operation.
16. The resistive change element array of claim 1 wherein said initialization driver circuits provide a single initialization pulse during an initialization operation.
17. The resistive change element array of claim 1 wherein said initialization driver circuits provide a series of initialization pulses during an initialization operation.
18. The resistive change element array of claim 1 wherein said initialization driver circuits provide a pulse train during an initialization operation.
19. The resistive change element array of claim 1 wherein said plurality of word lines is arranged parallel to said plurality of select lines.
20. The resistive change memory array of claim 1 wherein said resistive change elements are selected from the group consisting of two-terminal nanotube switching elements, metal oxide memory elements, and phase change memory elements.