MEMORY READING METHOD FOR RESISTANCE DRIFT MITIGATION
First Claim
1. A method for operating a memory cell, a memory state of the memory cell being represented by a configuration of amorphous material in the memory cell, a resistance of the memory cell drifting over a period of time, the method comprising:
- applying a plurality of electrical input signals to the memory cell;
measuring a plurality of electrical output signals from the memory cell resulting from the plurality of electrical input signals;
calculating an invariant component of the plurality of electrical output signals dependent on the configuration of amorphous material in the memory cell, the invariant component being substantially independent of a resistance drift characteristic of the memory cell over the period of time; and
determining a memory state of the memory cell based on the invariant component.
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Abstract
Techniques for reading phase change memory that mitigate resistance drift. One contemplated method includes apply a plurality of electrical input signals to the memory cell. The method includes measuring a plurality of electrical output signals from the memory cell resulting from the plurality of electrical input signals. The method includes calculating an invariant component of the plurality of electrical output signals dependent on the configuration of amorphous material in the memory cell. The method also includes determining a memory state of the memory cell based on the invariant component. In one embodiment of the invention, the method further includes mapping the plurality of electrical output signals to a measurements region of a plurality of measurements regions. The measurements regions correspond to memory states of the memory cell.
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Citations
25 Claims
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1. A method for operating a memory cell, a memory state of the memory cell being represented by a configuration of amorphous material in the memory cell, a resistance of the memory cell drifting over a period of time, the method comprising:
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applying a plurality of electrical input signals to the memory cell; measuring a plurality of electrical output signals from the memory cell resulting from the plurality of electrical input signals; calculating an invariant component of the plurality of electrical output signals dependent on the configuration of amorphous material in the memory cell, the invariant component being substantially independent of a resistance drift characteristic of the memory cell over the period of time; and determining a memory state of the memory cell based on the invariant component. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for operating a memory cell, a memory cell state being represented by a configuration of amorphous material in the memory cell, a resistance of the memory cell drifting over a period of time, the method comprising:
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applying at least one periodic input signal to the memory cell; measuring an amplitude of at least one harmonic frequency resulting from the at least one periodic input signal; calculating an invariant component based on the amplitude of the at least one harmonic frequency resulting from the at least one periodic input signal, the invariant component being dependent on the configuration of amorphous material in the memory cell, the invariant component being substantially independent of a resistance drift characteristic of the memory cell over the period of time; and determining the memory state of the memory cell based on the invariant component. - View Dependent Claims (9, 10)
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11. A memory controller for operating a memory cell, a memory cell state being represented by a configuration of amorphous material in the memory cell, a resistance of the memory cell drifting over a period of time, the memory controller comprising:
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a biasing unit configured to bias a memory cell with a plurality of electrical input signals; a measuring unit configured to measure a plurality of electrical output signals from the memory cell resulting from the plurality of electrical input signals; a calculating unit configured to calculate an invariant component of the plurality of electrical output signals dependent on the configuration of amorphous material in the memory cell, the invariant component being substantially independent of a resistance drift characteristic of the memory cell over the period of time; and a determining unit configured to determine a memory state of the memory cell based on the invariant component of the plurality of output electrical signals. - View Dependent Claims (12, 13, 14, 15, 16)
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17. A computer program product embodied in a computer usable memory comprising:
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computer readable program codes coupled to the computer usable medium for operating a memory cell, a memory cell state being represented by a configuration of amorphous material in the memory cell, a resistance of the memory cell drifting over a period of time, the computer readable program codes configured to cause the program to; apply a plurality of electrical input signals to the memory cell; measure a plurality of electrical output signals from the memory cell resulting from the plurality of electrical input signals; calculate an invariant component of the plurality of electrical output signals dependent on the configuration of amorphous material in the memory cell, the invariant component being substantially independent of a resistance drift characteristic of the memory cell over the period of time; and determine a memory state of the memory cell based on the invariant component. - View Dependent Claims (18, 19, 20, 21, 22, 23)
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24. A computer program product embodied in a computer usable memory comprising:
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computer readable program codes coupled to the computer usable medium for operating a memory cell, a memory cell state being represented by a configuration of amorphous material in the memory cell, a resistance of the memory cell drifting over a period of time, the computer readable program codes configured to cause the program to; apply at least one periodic input signal to the memory cell; measure an amplitude of at least one harmonic frequency resulting from the at least one periodic input signal; calculate an invariant component based on the amplitude of the at least one harmonic frequency resulting from the at least one periodic input signal, the invariant component being dependent on the configuration of amorphous material in the memory cell, the invariant component being substantially independent of a resistance drift characteristic of the memory cell over the period of time; and determine the memory state of the memory cell based on the invariant component.
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25. A memory device comprising:
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a plurality of memory cells, each memory cell including a memory state represented by a configuration of amorphous material in the memory cell, a resistance of the memory cell drifting over a period of time; and a controller configured to; (a) receive an address specifying a memory location to be read; (b) select the memory cell specified; (c) apply a plurality of electrical input signals to the memory cell; (d) measure a plurality of electrical output signals from the memory cell resulting from the plurality of electrical input signals; (e) calculate an invariant component of the plurality of electrical output signals dependent on the configuration of amorphous material in the memory cell, the invariant component being substantially independent of a resistance drift characteristic of the memory cell over the period of time; and (f) determine a memory state of the memory cell based on the invariant component.
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Specification