MRAM Read Circuit With Current Limiting for Stable Sensing
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Solution Overview
Problem
Existing magnetic memory devices face challenges in maintaining a stable read performance due to fluctuations in read current, which can lead to read disturbances and breakdowns, especially when reading data from magnetoresistive random-access memory (MRAM) cells.
Innovation Solution
The magnetic memory device employs a current-limiting transistor to regulate the read current to a constant value (Ird_max) during the read operation, preventing excessive current flow and minimizing disturbances or breakdowns, thereby maximizing the voltage difference (ΔV) for accurate data determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If read current is increased to maximize voltage difference between memory cell states, then data determination accuracy is improved, but read disturbances and breakdowns occur
Solution Approach 1:
The patent applies dynamics by making the read current controllable and adjustable through a current control circuit. The read current is dynamically optimized to a specific value that maximizes the voltage difference between parallel and anti-parallel states while preventing read disturbances and breakdowns, rather than using a fixed high current that causes reliability issues.
Solution Approach 2:
The patent changes the read current parameter to an optimized specific value determined through sensitivity analysis. By adjusting this parameter, the system achieves maximum voltage difference for accurate data determination while maintaining reliability by avoiding excessive current that causes read disturbances and breakdowns.
2Reliability
If read current is limited to prevent read disturbances and breakdowns, then read stability is improved, but voltage difference between memory cell states decreases
Solution Approach 1:
The patent uses a current control circuit to dynamically adjust the read current to an optimized specific value. This dynamic control ensures the current is high enough to produce sufficient voltage difference for accurate data determination while being limited enough to prevent read disturbances and breakdowns, resolving the contradiction between stability and precision.
Solution Approach 2:
The patent optimizes the read current parameter to a specific value that balances reliability and measurement precision. Through sensitivity analysis, the optimal current value is determined to maximize voltage difference while maintaining stability, and this parameter is controlled through the current control circuit.
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
This approach enhances read performance by stabilizing the read current, reducing errors, and preventing disturbances or breakdowns, while allowing for high-integration and three-dimensional stacking of memory cells.
Implementation Method 1
a magnetoresistive effect element including a first ferromagnetic layer, a nonmagnetic layer, and a second ferromagnetic layer which are stacked in this order from below upward
Data Source
AI summary
A magnetic memory device according to an embodiment includes a magnetic memory device includes first and second interconnect, a memory cell, a transistor, first and second sense amplifiers, and a control circuit. The memory cell includes a magnetoresistive effect element and a selector element. The magnetoresistive effect element and the selector element are coupled in series between the first and second interconnect. In a read operation, the control circuit is further configured to: charge the first interconnect to a first voltage; and discharge the first interconnect via the transistor by applying a second voltage to a gate end of the transistor.