Method of operating and apparatus of memristor arrays with diagonal lines interconnect between memristor cells

• US 9,691,479 B1
• Filed: 04/29/2016
• Issued: 06/27/2017
• Est. Priority Date: 04/29/2016
• Status: Active Grant

• Current Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Original Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Inventors: Buchanan, Brent, Zheng, Le, Merced Grafals, Emmanuelle J.
• Primary Examiner(s): Lam, David
• Application Number:
  US15/142,995
• Time in Patent Office: 424 Days
• Field of Search: 365148, 365 51, 365100, 365158
• CPC Class Codes: G11C 13/0002 using resistive RAM [RRAM] elements
• CPC Class Codes: G11C 13/0026 Bit-line or column circuits
• CPC Class Codes: G11C 13/0028 Word-line or row circuits
• CPC Class Codes: G11C 13/003 Cell access
• CPC Class Codes: G11C 13/004 Reading or sensing circuits or methods
• CPC Class Codes: G11C 13/0069 Writing or programming circuits or methods
• CPC Class Codes: G11C 2013/0076 Write operation performed depending on read result
• CPC Class Codes: G11C 2013/0088 Write with the simultaneous writing of a plurality of cells
• CPC Class Codes: G11C 2013/0092 Write characterized by the shape, e.g. form, length, amplitude of the write pulse
• CPC Class Codes: G11C 2213/71 Three dimensional array
• CPC Class Codes: G11C 2213/74 Array wherein each memory cell has more than one access device
• CPC Class Codes: G11C 2213/79 Array wherein the access device being a transistor

Abstract

A method of operating a plurality of memristive cells coupled as a memristor array includes initializing a first select line, and, in parallel for a number of memristor cells in the first select line, determining whether a level of conductance of the memristor cells in the first select line are within a tolerance of a reference conductance, and, in response to a determination that the level of conductance is not within the tolerance of the reference conductance, adjusting the level of conductance for the memristor cells in the first select line.

Claims

1. A method of operating a plurality of memristive cells coupled as a memristor array comprising:

initializing a first select line; and

in parallel for a number of memristor cells in the first select line;

determining whether a level of conductance of the memristor cells in the first select line are within a tolerance of a reference conductance; and

in response to a determination that the level of conductance is not within the tolerance of the reference conductance, adjusting the level of conductance for the memristor cells in the first select line.

2. The method of claim 1, comprising in response to a determination that the level of conductance is within a tolerance of a reference conductance:

initializing a second select line; and

in parallel for a number of memristor cells in the second select line;

determining whether a level of conductance of the memristor cells in the second select line are within a tolerance of a reference conductance; and

in response to a determination that the level of conductance is not within a tolerance of a reference conductance, adjusting the level of conductance for the memristor cells in the second select line.

3. The method of claim 1, comprising:

determining whether a final select line within the memristor array has been initialized; and

in response to a determination that the final select line within the memristor array has not been initialized, incrementing initialization of select lines to a subsequent select line.

4. The method of claim 1, wherein determining whether the level of conductance of the memristor cells in the first select line are within the tolerance of the reference conductance, and in response to a determination that the level of conductance is not within a tolerance of the reference conductance, adjusting the level of conductance for the memristor cells in the first select line comprises:

performing a read function on the memristor cells in the first select line;

sensing the conductance level of the memristor cells in the first select line;

comparing the conductance level of the memristor cells in the first select line with a reference conductance;

determining if the conductance level of the memristor cells in the first select line are greater than the reference conductance;

in response to a determination that the conductance level of the memristor cells in the first select line are greater than the reference conductance, modifying the reset conditions and performing a reset operation; and

in response to a determination that the conductance level of the memristor cells in the first select line are less than the reference conductance, modifying the set conditions and performing a set operation.

5. The method of claim 4, wherein modifying the set and reset conditions comprises modifying the voltage amplitude, modifying the pulse duration, or modifying the number of consecutive pulses.

6. The method of claim 1, comprising:

determining the dimensions of the memristor array;

if the dimension of the memristor array is n by n memristive cells, adjusting the level of conductance for the memristor cells within the memristor array; and

if the dimension of the memristor array is m by n memristive cells, determining if m is an integer of n;

if m is an integer of n, analyzing in series the m by n memristor array as a number of parsed n by n arrays where the number of parsed n by n arrays is equal to the quotient of m and n; and

if m is not an integer of n;

analyzing in series the m by n memristor array as a number of parsed n by n arrays where the number of parsed n by n arrays is equal to the quotient of m and n;

modifying the architecture of the remainder m by n memristor array, and

analyzing in series with the parsed n by n arrays, the remainder m by n memristor array.

7. The method of claim 1, wherein:

the reference conductance comprises a plurality of reference conductance values, each of the plurality of reference conductance value being assigned to one of the memristor cells; and

determining whether a level of conductance of the memristor cells in the first select line are within a tolerance of a reference conductance comprises, for each of the memristor cells;

determining whether a level of conductance of the memristor cell is within a tolerance of its assigned reference conductance value.

8. A memristor array comprising:

a number of row lines;

a number of column lines intersecting the row lines to form a number of junctions;

a number of memristive cells coupled between the row lines and the column lines at the junctions;

a number of first diagonal lines coupled between the memristive cells in a first direction; and

a number of second diagonal lines coupled between the memristive cells in a second direction,

wherein the first diagonal lines and the second diagonal lines each couple at least two memristive cells via diagonally run interconnects with respect to the row lines and the column lines, and

wherein the memristive cells are trained via application of a voltage via the first and second diagonal lines.

9. The memristor array of claim 8, further comprising a number of select line drivers to select a row of the memristor array, wherein selection of a first select line driver during a programming process causes a programming voltage to be directed via the first and second diagonal lines coupled to the first select line driver.

10. The memristor array of claim 9, comprising:

a column decoder comprising;

a first set of a number of electrode driver and electrode sensor pairs; and

a first set of switches for each electrode driver and electrode sensor pair of the first set of electrode driver and electrode sensor pairs to switch between the electrode drivers and the electrode sensors of the first set of electrode driver and electrode sensor pairs; and

a row decoder comprising;

a second set of a number of electrode driver and electrode sensor pairs; and

a second set of switches for each electrode driver and electrode sensor pair of the second set of electrode driver and electrode sensor pairs to switch between the electrode drivers and the electrode sensors of the second set of electrode driver and electrode sensor pairs;

wherein the electrode drivers of the first and second sets of the electrode driver and electrode sensor pairs drive a voltage to write to a number of the memristive cells, and

wherein the electrode sensors of the first and second sets of the electrode driver and electrode sensor pairs sense a current from a number of the memristive cells.

11. The memristor array of claim 10, wherein selection between the electrode drivers and the electrode sensors of the first and second sets of electrode driver and electrode sensor pairs are performed in parallel to allow for each memristor cell in a first select line to be simultaneously either programmed or read.

12. The memristor array of claim 8, wherein the memristor cells are multi-level cells wherein the row lines, the column lines, the first diagonal lines, and the second diagonal lines are positioned on separate levels of the memristor cells.

13. The memristor array of claim 8, wherein the memristive cells comprise two transistors and one-resistor (2T1R).

14. The memristor array of claim 8, wherein the memristive cells comprise one transistor and one-resistor (1T1R).

15. The memristor array of claim 8, wherein the memristor array is a memristor memory array.

16. The memristor array of claim 8, wherein the memristor array is a memristive accelerator array.

17. A method of operating a memristor array, comprising:

performing a read function on a plurality of memristor cells on a select line;

sensing a conductance level of the plurality of memristor cells on the select line;

determining whether the conductance level of the plurality of memristor cells on the select line are greater than a reference conductance by comparing the conductance level of the plurality of memristor cells on first select line to the reference conductance;

in response to a determination that the conductance level of the plurality of memristor cells on the select line are greater than the reference conductance, modifying reset conditions of the plurality of memristor cells and performing a reset operation; and

in response to a determination that the conductance level of the plurality of memristor cells on the select line are less than the reference conductance, modifying set conditions of the plurality of memristor cells and performing a set operation.

18. The method of claim 17, wherein:

the reference conductance comprises a plurality of reference conductance values, each of the plurality of reference conductance value being assigned to one of the plurality of memristor cells; and

determining whether the conductance level of the plurality of memristor cells on the select line are greater than a reference conductance comprises, for each of the memristor cells;

comparing the conductance level of the memristor cell to its assigned reference conductance value.

19. The method of claim 17, wherein the plurality of memristor cells are located along a diagonal line to which the first select line is coupled.

20. The method of claim 17, wherein each of the plurality of memristor cells are on different row line and column line pairs.