What is MRAM? – A promising next-generation memory

MRAM (Magnetoresistive Random Access Memory) is a type of memory that combines non-volatility, meaning it retains data even when the power is turned off, with high-speed read/write performance.

Traditional memory technologies each had their own distinct roles and limitations.

SRAM: Extremely fast but volatile, meaning its contents are lost when the power is turned off. It is used for temporary data and working memory during program execution.

Flash memory: While it can retain data even when the power is turned off, it takes time to rewrite data and is not suitable for frequent updates.

 
Thus, there was a significant gap between "fast but easily lost memory" and "memory that never loses but is slow."

MRAM emerged to fill that gap and is attracting attention as a next-generation memory that simultaneously satisfies the requirements of "high speed, non-volatility, and high durability."

In recent years, its adoption has been increasing in fields where high speed and reliability are required, such as embedded devices, industrial applications, and edge AI.

Figure 1: Positioning of SRAM, MRAM, and Flash Memory

The basic principles of MRAM – memory that stores information using magnetism.

MRAM stores data using magnetic properties rather than electric charge.

For example, SRAM stores data using flip-flop circuits, but the data is lost if the power supply is interrupted.
On the other hand, MRAM stores information based on the direction of magnetization, and this state does not change even when the power is turned off, so it can retain data.

Figure 2: Differences between SRAM and MRAM

The magnetic tunnel junction (MTJ), which is the memory element of an MRAM cell, consists of two magnetic layers (a fixed layer and a free layer) and a thin tunnel film between them.

The electrical resistance of the element changes when the magnetization direction of the free layer changes, and the difference in this resistance value is read out as "0" or "1".

Figure 3: Mechanism of resistance change in MTJ

Key Features of MRAM

The key features of MRAM can be summarized as follows:

- Achieving both non-volatility and high speed

The graph below compares a code flash-equipped microcontroller (MCU) from Renesas Electronics with the latest MRAM-integrated MCU, the "RA8P1".
MRAM offers significantly faster rewrite speeds compared to flash memory, resulting in a reduction of approximately 98 % in memory rewrite time.
This will significantly improve the performance of processes that frequently involve rewriting, such as firmware updates and log writing.

Figure 4: Comparison of memory rewrite times

*This value is a representative value and represents the pure rewrite time. It does not include overhead such as pre- and post-processing or control.

• High rewrite durability

Because MRAM has no theoretical upper limit on the number of times the magnetization of the magnetic material can be reversed, it is suitable for applications that require repeated writing.

Flash memory has limitations on the number of write cycles, especially for code flash memory, which is limited to several thousand to tens of thousands of cycles. On the other hand, MRAM has high durability in both its code and data areas.

Therefore, this memory is suitable for systems that require frequent data updates, such as updating settings and logging data.

Figure 5: Comparison of rewrite cycles

・Low power consumption

MRAM is a type of memory that does not require standby power for data retention, making it suitable for devices that require low power consumption.
Renesas' latest MRAM-integrated MCU, the "RA8P1," has been confirmed to reduce operating current consumption by approximately 47 % compared to conventional products, according to their measurements ^*.

*This comparison is with previous products from Renesas Electronics. The calculations are based on representative values under High-speed mode and DC/DC mode operation. (Since previous products were single-core products, the RA8P1 uses representative values with CPU1 operating and CPU0 in deep sleep mode.)

Figure 6: Comparison of current consumption

Main uses of MRAM – in what situations is it used?

MRAM is already in practical use, and its applications are gradually expanding.

Embedded and IoT devices

​MRAM is increasingly being used for storing configuration data.
The features of MRAM, such as byte-by-byte rewriting, high-speed access, and data retention during power outages, make it suitable for log storage and field updates.

Industrial applications

Because MRAM stores data in a magnetized state rather than an electric charge, it is unaffected by leakage (electrical charge leakage) which increases at high temperatures, achieving high reliability even in industrial applications where continuous operation keeps the environment at high temperatures.

Its adoption is expanding in industrial controllers, motion control equipment, and monitoring systems.

Storage

Leveraging its rewrite endurance and power outage resistance, MRAM is increasingly being used for applications such as SSD internal caching, state management, and log storage. MRAM 's characteristics are particularly beneficial in applications requiring frequent and high-speed writing.

aerospace

In the aerospace field, conditions that can easily affect conventional memory, such as high-radiation environments, are expected, but MRAM exhibits relatively stable operation.
Therefore, it has a proven track record in applications such as satellite attitude control and control computers. Its resistance to degradation even with a high number of rewrite cycles is highly valued.

Medical devices

In medical devices, data retention and high reliability are paramount, and MRAM, which can retain data without a battery, is a highly compatible memory type.
Examples of its use have also been reported in medical devices, analytical instruments, and other applications.

Figure 7: Main applications of MRAM

Summary

MRAM is attracting attention as a next-generation memory that solves the problems of conventional memory by combining non-volatility and high speed.
Due to its characteristics, its use is expanding in fields that require high reliability and performance, such as embedded devices, industrial applications, and storage.

Chapter 2, "Applications," provides a detailed explanation of the applicability of MRAM in magnetic field environments. Please be sure to read it as well.

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