MRAM Sensing Amplifier Using Dual Reference Voltages for Read Margin
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Solution Overview
Problem
Magnetic random access memory (MRAM) faces challenges with narrow read signal margins due to fixed reference voltages that are not adjusted for environmental variations, leading to inefficient data reading.
Innovation Solution
Implementing a sensing amplifier that uses dual state reference voltages to distinguish the parallel and anti-parallel states of STT MRAM cells, enhancing the read signal margin without requiring a mid-point reference voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed reference voltage is used for reading MRAM cells, then the reference voltage is simple to implement, but the read signal margin becomes narrow due to environmental variations
Solution Approach 1:
The reference voltage is segmented into two distinct reference voltages (first reference voltage and second reference voltage) corresponding to the two stable states (parallel and anti-parallel) of the MRAM cell. This segmentation allows each reference voltage to be optimized for its specific state, improving the read signal margin for both states without requiring a complex mid-point reference voltage.
Solution Approach 2:
The reference voltage is made dynamic by selecting different reference voltages based on the expected state of the MRAM cell. The sensing amplifier dynamically switches between using the first reference voltage and the second reference voltage depending on which state is being read, allowing adaptation to environmental variations while maintaining simple implementation.
2Reliability
If a mid-point reference voltage is used to distinguish parallel and anti-parallel states, then the read margin may be improved, but the device complexity increases
Solution Approach 1:
Instead of generating a single mid-point reference voltage, the system segments the reference voltage into two distinct voltages corresponding to the two stable states. This eliminates the need for complex mid-point generation circuitry while maintaining the ability to distinguish between parallel and anti-parallel states effectively.
Solution Approach 2:
The patent uses reference cells that copy the stable states of the data cells to generate reference voltages. By creating reference cells with known parallel and anti-parallel states, the system obtains reference voltages that naturally correspond to the two states without requiring complex mid-point calculation or generation circuitry.
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
The dual state reference voltages significantly improve the read signal margin, ensuring accurate data reading across varying environments.
Implementation Method 1
Magnetic random access memory (MRAM) is a nonvolatile memory technology that uses magnetization to represent stored data. MRAMs are beneficial in that they retain stored data in the absence of electricity.
Implementation Method 2
the way for reading one cell of the MRAM is to compare a read voltage from the cell of the MRAM and a reference voltage which distinguishes the cell in the parallel (P) state or in the anti-parallel (AP) state, so as to sense the stored data
Data Source
AI summary
A sensing amplifier of a memory array, a memory device and a data read method with two state reference voltages are provided. The sensing amplifier comprises a sampling circuit, a latch circuit, and a reset circuit. The sampling circuit compares data voltages, a first state reference voltage, and a second state reference voltage according to a bit line pre-charge signal and a word line to generate a first sampling signal on the output node and a second sampling signal on the inverted output node. The latch circuit implements that the first sampling signal and the second sampling signal are inverted signals and latches the first sampling signal on an output node and the second sampling signal on the inverted output node.