Method of writing to a spin torque magnetic random access memory
AssigneeEverspin Technologies, Inc.
InventorsMichael Schneider, Dimitri Houssameddine, Jon Slaughter
Life of this patent
Estimating the term…
Abstract
Circuitry and a method provide an increased tunnel barrier endurance (lifetime) previously shortened by dielectric breakdown by providing a pulse of opposite polarity associated with a write pulse. The pulse of opposite polarity may comprise equal or less width and amplitude than that of the write pulse, may be applied with each write pulse or a series of write pulses, and may be applied prior to or subsequent to the write pulse.
Claims23
A memory device comprising:
- an array of ST-MRAM memory cells configured to:
- store data according to a write pulse;
- and
- circuitry coupled to the array and configured to:
- provide the write pulse and a read pulse to the memory array;
- and
- provide to the memory array a charging pulse having an opposite polarity from the write pulse or the read pulse,
- wherein the circuitry further comprises a register to record a number of accesses to an assembly of memory cells of the array of memory cells, wherein the circuitry is configured to provide the charging pulse to the assembly of memory cells when the number of accesses reaches a threshold value.
A method of accessing a magnetoresistive bit, comprising:
- providing a first charging pulse having a first polarity to the bit, wherein the first charging pulse does not determine a desired state for the bit;
- providing a write pulse sequence to the bit to switch the bit to the desired state, the write pulse sequence including one or more write pulses having a second polarity that is opposite the first polarity, wherein the first charging pulse is provided before the write pulse sequence;
- after providing the write pulse sequence, providing a read pulse to the bit, wherein the read pulse is used in evaluating a bit state for the bit, and
- providing a second charging pulse having a polarity opposite a polarity of the read pulse.
A method of accessing a magnetoresistive bit, comprising:
- providing a charging pulse having a first polarity to the bit, wherein the charging pulse does not determine a desired state for the bit;
- sampling the bit to provide a sampled voltage;
- after sampling the bit, applying a reset current pulse to the bit to set the bit to a first state, wherein the reset current pulse has a second polarity that is opposite the first polarity;
- after applying the reset current pulse, resampling the bit to provide an evaluation voltage;
- and
- comparing the evaluation voltage and the sampled voltage to determine a bit state for the bit.
A method of accessing a magnetoresistive bit, comprising:
- providing a first charging pulse having a first polarity to the bit, wherein the first charging pulse does not disturb the bit;
- providing a read pulse having a second polarity to the bit, wherein the first polarity and the second polarity are opposite, wherein the first charging pulse is provided subsequent to providing the read pulse;
- and
- determining a bit state for the bit based on the read pulse.
Dependencies are inferred from the claim text.