Self-referenced sense amplifier for spin torque MRAM
First Claim
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1. A method of reading data from each of a plurality of memory cells in a spin torque magnetoresistive memory array, the method comprising:
- applying a read voltage across a source line and a bit line coupled to a memory cell;
applying a write current in a first direction through the memory cell to write a first state;
reapplying the read voltage across the source line and the bit line; and
applying a programmable offset current to the one of the bit line or the source line, wherein the programmable offset current is applied during, but after initiation of, the reapplying step.
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Abstract
Circuitry and a method provide a plurality of timed control and bias voltages to sense amplifiers and write drivers of a spin-torque magnetoresistive random access memory array for improved power supply noise rejection, increased sensing speed with immunity for bank-to-bank noise coupling, and reduced leakage from off word line select devices in an active column.
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Citations
23 Claims
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1. A method of reading data from each of a plurality of memory cells in a spin torque magnetoresistive memory array, the method comprising:
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applying a read voltage across a source line and a bit line coupled to a memory cell; applying a write current in a first direction through the memory cell to write a first state; reapplying the read voltage across the source line and the bit line; and applying a programmable offset current to the one of the bit line or the source line, wherein the programmable offset current is applied during, but after initiation of, the reapplying step. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of reading data from each of a plurality of memory cells in a spin torque magnetoresistive memory array, the method comprising:
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applying a read voltage across a magnetic tunnel junction within a memory cell; converting a current through the magnetic tunnel junction under the applied read voltage into a sample voltage; storing the sample voltage in a capacitor; applying a first write current through the magnetic tunnel junction to reset the memory cell to a first state; reapplying the read voltage across the magnetic tunnel junction; using the sample voltage and a programmable offset current to create a reference current; converting a difference between the reference current and the current through the magnetic tunnel junction under the reapplied read voltage to generate an evaluation voltage; and comparing the sample voltage and the evaluation voltage. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A spin torque magnetoresistive memory array having a plurality of memory cells, each memory cell of the plurality of memory cells selectively coupled between a respective bit line of a plurality of bit lines and a respective source line of a plurality of source lines, the spin torque magnetoresistive memory array comprising:
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column selection circuitry coupled to first and second ends of each source line of the plurality of source lines and to a first end of each bit line of the plurality of bit lines and configured to select a specific bit line of the plurality of bit lines; global bias circuitry configured to provide a plurality of timed bias voltages; sense amplifiers and write drivers coupled between the column selection circuitry and the global bias circuitry, the sense amplifiers and write drivers configured to; receive the timed bias voltages; and for a memory cell coupled to the specific bit line; apply a read voltage across the source line and the specific bit line coupled to the memory cell; apply a write current in a first direction through the memory cell to write a first state; reapply the read voltage across the source line and the specific bit line coupled to the memory cell; and apply a programmable offset current to the specific bit line. - View Dependent Claims (22, 23)
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Specification