Non-volatile latch with magnetic junctions

• US 7,082,053 B1
• Filed: 12/24/2003
• Issued: 07/25/2006
• Est. Priority Date: 12/24/2003
• Status: Expired due to Fees

• Current Assignee: Monterey Research, LLC (Vector Capital Corporation)
• Original Assignee: Silicon Magnetic Systems Incorporated
• Inventors: Jenne, Fredrick L., Gibbs, Gary A.
• Primary Examiner(s): Nguyen, Tuan T.
• Assistant Examiner(s): LE, TOAN K
• Application Number:
  US10/745,725
• Time in Patent Office: 944 Days
• Field of Search: 365/173, 365/225.5, 365/158, 365/189.05, 365/50
• US Class Current: 365/173
• CPC Class Codes: G11C 14/0081 and the nonvolatile element is a magnetic RAM [MRAM] element or ferromagnetic cell

Abstract

A memory storage circuit is provided which includes a plurality of magnetic elements each configured to store bits in a first or a second logic state. The storage circuit may further include a plurality of transistors coupled to at least two of the magnetic elements. Such a plurality of transistors may be collectively configured to store bits in the first and second logic states as well. The memory storage circuit may include circuitry configured to load bits from a set of the magnetic elements into the plurality of transistors. Another circuit is provided which includes a magnetic element interposed between a bit line and an electrode. The circuit may further include a first set of circuitry configured to induce current flow through the magnetic element in a direction from the electrode to the bit line. A method for operating a memory storage circuit with the aforementioned configurations is also provided.

Claims

1. A memory storage circuit, comprising:

a plurality of magnetic elements each configured to store bits in a first logic state or a second logic state;

a plurality of transistors coupled to at least two of the magnetic elements, wherein the plurality of transistors are collectively configured to store bits in the first and second logic states;

a first set of circuitry configured to load bits from a set of the magnetic elements into the plurality of transistors, wherein the first set of circuitry comprises a first set of conductive structures configured to pass current through the set of magnetic elements; and

a second set of circuitry configured to program the set of magnetic elements, wherein the second set of circuitry comprises;

a second set of conductive structures configured to induce respective magnetic fields about each of the set of magnetic elements; and

a program transistor coupled between the set of magnetic elements and configured to enable current flow among the second set of conductive structures.

2. The memory storage circuit of claim 1, wherein the circuitry is substantially absent of cross-over lines.

3. The memory storage circuit of claim 1, wherein the first set of conductive structures comprises a bit line and an electrode coupled to opposing sides of each of the set of magnetic elements, and wherein the circuitry is configured to induce current flow through each of the magnetic elements in a direction from the electrode to the bit line.

4. The memory storage circuit of claim 1, wherein the second set of conductive structures comprises a first series of connected conductive structures comprising at least two elements respectively aligned with opposing sides of one of set of magnetic elements.

5. The memory storage circuit of claim 4, wherein the second set of conductive structures further comprises a second series of connected conductive structures comprising at least two elements respectively aligned with opposing sides of the other of the set of magnetic elements, and wherein the first and second series of connected conductive structures are arranged such that the first and second logic states may be programmed into the set of magnetic elements, respectively.

6. The memory storage circuit of claim 1, further comprising a subcircuit configured to alter current applications along at least one of the first and second sets of conductive structures.

7. The memory storage circuit of claim 1, wherein the set of magnetic elements comprises a differential pair of magnetic elements.

8. The memory storage circuit of claim 1, wherein the set of magnetic elements comprises a selected magnetic element and a plurality of reference magnetic elements.

9. The memory storage circuit of claim 1, wherein the set of magnetic elements are coupled to a common program current source.

10. A circuit, comprising:

a pair of magnetic elements respectively configured to store bits of opposing logic states, wherein each of the a-magnetic elements is interposed between a respective bit line and a respective electrode;

a plurality of transistors coupled to the pair of magnetic elements which are collectively configured to store bits of opposing logic states;

a first node interposed between the plurality of transistors and a respective electrode of one of the pair of magnetic elements;

a second node interposed between the plurality of transistors and a respective electrode of the other of the pair of magnetic elements; and

a first set of circuitry configured to load bits from the pair of magnetic elements to the plurality of transistors by inducing current flow through each of the pair of magnetic elements in a direction from their respective electrodes to their respective bit lines.

11. The circuit of claim 10, further comprising a second set of circuitry configured to load data from the plurality of transistors to the magnetic element.

12. The circuit of claim 10, further comprising a second set of circuitry configured to program the pair of magnetic elements, wherein the second set of circuitry comprises:

a first series of connected conductive structures comprising at least two elements respectively aligned with opposing sides of one of the pair of magnetic elements and collectively configured to induce a magnetic field sufficient to program the one magnetic element;

a second series of connected conductive structures comprising at least two elements respectively aligned with opposing sides of another of the pair of magnetic elements and collectively configured to induce a magnetic field sufficient to program the other magnetic element; and

a program transistor configured to enable current flow between the first and second series of connected conductive structures such that the one and other magnetic elements are programmed in opposing logic states.

13. A method for operating a latch, comprising:

charging up first and second nodes of a volatile portion of the latch, wherein the first and second nodes are respectively arranged at opposing ends of the volatile portion;

inducing current flow through two magnetic elements respectively arranged within first and second regions of a non-volatile portion of the latch, wherein the first and second regions are respectively arranged in alignment with the opposing ends of the volatile portion, and wherein the current flow is directed from electrodes respectively arranged adjacent to the two magnetic elements to bit lines respectively arranged on sides of the two magnetic elements opposing the electrodes; and

loading the first and second nodes to have logic states which correspond to resistance levels within the magnetic elements in the first and second regions, respectively.

14. The method of claim 13, wherein the step of loading comprises discharging the first and second nodes at different rates.

15. The method of claim 13, wherein the step of loading comprises discharging the first and second nodes until the second node reaches a threshold voltage of a transistor coupled thereto such that the second node is pulled low and the first node is pulled high.