Crossbar Memory Reading Without Isolation Elements
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Solution Overview
Problem
Crossbar memory structures face challenges in accurately reading the state of a specific memory element due to interference from other elements along the connected wires, requiring additional isolation elements that decrease memory array density and increase costs.
Innovation Solution
A method that involves selecting a column line connected to the target memory element, storing the initial electric current, fully selecting the element, and subtracting the stored current from the measured current to isolate the target element's signal, allowing for accurate state reading without additional isolation elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional isolation elements are added to read specific memory elements, then reading accuracy is improved, but memory array density decreases and costs increase
Solution Approach 1:
The patent applies preliminary action by measuring the current through the selected column line before fully selecting the target memory element. This initial measurement captures the contribution of unselected memory elements, allowing the patent to subtract this interference later and obtain the accurate state of the target element without needing isolation elements.
Solution Approach 2:
The patent converts the harmful interference from unselected memory elements into a beneficial signal for subtraction. By measuring the total current including interference first, then subtracting the interference component, the patent transforms the previously harmful cross-talk into a correctable parameter that enables accurate reading without isolation elements.
2Measurement precision
If additional isolation elements are added to read specific memory elements, then reading accuracy is improved, but manufacturing costs increase
Solution Approach 1:
The patent extracts the interference signal from the total measured current by measuring the column line current before the target element is fully selected. This extracted interference component can then be subtracted from the total measurement, eliminating the need for additional isolation elements and reducing manufacturing complexity.
Solution Approach 2:
The patent enables the crossbar array to read its own elements accurately using its existing structure and control mechanisms. By utilizing the natural current flow through selected column lines and row lines, the system self-isolates the target element through sequential selection, eliminating the need for external isolation elements and reducing manufacturing costs.
3Difficulty of detecting and measuring
If sensing conditions are applied to read memory elements, then state detection is enabled, but interference from other elements along connected wires adversely affects the sensing
Solution Approach 1:
The patent segments the reading process into distinct phases: first measuring the column line current with the target element partially selected, then measuring again with the target element fully selected. This segmentation allows the system to separate the target element's contribution from the interference of other elements along the connected wires.
Solution Approach 2:
The patent uses feedback by measuring the total current through the selected column line and using this information to determine the state of the target memory element. The measured current serves as feedback that, when processed by subtraction of the interference component, yields the accurate state of the target element despite the presence of interfering elements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate reading of memory elements within a crossbar memory structure without the need for isolation elements, resulting in a higher memory density and reduced design, implementation, and manufacturing costs.
Implementation Method 1
A memristive element is a device which changes the state of its resistance based on an applied programming condition
Implementation Method 2
The state of a memory element may be determined by applying a sensing condition such as a sense voltage or a sense electric current
Data Source
AI summary
A method for reading the state of a memory element within a crossbar memory array includes storing a first electric current sensed from a half-selected target memory element within the crossbar memory array; and outputting a final electric current based on the stored first electric current and a second electric current sensed from the target memory element when the target memory element is fully selected.