Renesas launches MCU test chip with integrated STT-MRAM, targeting IoT and edge intelligence

Renesas Electronics recently announced that it has successfully developed a test chip for spin-transfer torque magnetoresistive random access memory (STT-MRAM), which is expected to provide a powerful alternative to conventional flash memory chips for microcontrollers (MCUs) with demanding performance, thanks to its superior read and write performance.

As the Internet of Things (IoT) and artificial intelligence (AI) technologies advance at a rapid pace, MCUs in endpoint devices must deliver higher performance than ever before to meet growing demands. Renesas Electronics said of their work on memory technology: “The CPU clock frequency of high-performance MCUs has reached hundreds of megahertz. To further improve performance, we need to increase the read speed of embedded non-volatile memories to minimize the gap between them and the CPU clock frequency.”

STT-MRAM, often referred to as MRAM, is a new memory technology that aims to bridge the performance gap between non-volatile but relatively slow flash memory and volatile but fast dynamic and static RAM (such as SRAM and DRAM). It is based on the magnetic storage principle of spin rather than the traditional charge or current storage method. Although MRAM's write speed has been proven to be quite high, its read operation has traditionally been delayed - this is the focus of Renesas Electronics' research and development work.

To improve the read speed, Renesas' test chip uses two new mechanisms: one is to align the reference current of a given chip with the center of the cell distribution according to actual tests; the other is to reduce the offset of the read amplifier. Combining these innovations with a new connection method, the chip achieves what Renesas calls "the world's fastest random read access time" - just 4.2 nanoseconds (ns), which means it can run smoothly at frequencies of 200MHz or even higher.

In addition, Renesas Electronics has also improved the write performance of the chip using technology they first developed in December 2021. By adjusting the step-down voltage from input to output, they succeeded in improving performance by 80%, allowing the test chip to continuously write at a speed of 10.4MB/s. Finally, to increase the flexibility of the chip, Renesas Electronics has also integrated a 0.3Mb one-time programmable (OTP) memory based on MRAM memory cell breakdown technology, which can be written in the field when needed.

Renesas Electronics presented their important research results at the 2024 International Solid-State Circuits Conference (ISSCC 2024), but they have not yet given specific information on the timeline for commercialization of the technology. Nevertheless, this breakthrough undoubtedly provides new development directions and possibilities for high-performance MCUs in the fields of IoT and artificial intelligence.