Ultra-low-power MCUs for next-generation smart home appliances

Renesas Electronics Corporation has released the new 16-bit RL78/L23 MCU group, extending its low-power RL78 family. Running at 32MHz, the RL78/L23 MCUs combine industry-leading low-power performance with essential features, including dual-bank flash memory, segment LCD control, and capacitive touch functionality, to support smart home appliances, consumer electronics, IoT, and metering systems. These compact, cost-effective devices address the performance and power requirements of modern display-based HMI applications.

The MCU group is optimised for ultra-low power consumption and is ideal for battery-powered applications that spend the majority of their time in standby. They provide an active current of just 109μA/MHz and a standby current as low as 0.365μA, along with a fast 1μs wake-up time to help minimise CPU activity. The LCD controller’s new reference mode, VL4, reduces the LCD operating current by approximately 30% compared to the existing RL78/L1X group. The MCUs come with SMS (SNOOZE Mode Sequencer), which allows dynamic LCD segment display without CPU intervention. By offloading tasks to the SMS, the devices minimise CPU wake-ups and contribute to system-level power savings. These innovations greatly extend battery life, simplify design and lower replacement costs, while minimising environmental impact.

The device offers a wide operating voltage range of 1.6V to 5.5V, which supports direct operation from 5V power supplies typically used in home appliances and industrial systems. This capability lowers the necessity for external voltage regulators. The MCUs also integrate key components, such as capacitive touch sensing, a temperature sensor, and an internal oscillator, thereby reducing BOM cost and PCB size.

Designed to meet the dynamic needs of the HMI market, the MCU group integrates a suite of advanced features in a compact, cost-effective package. Its built-in segment LCD controller and capacitive touch realise sleek, responsive user interfaces for products such as induction cooktops and HVAC systems. The IH timer (Timer KB40) enables precise multi-channel heat control, which is crucial in smart kitchen appliances, such as rice cookers and IH cooktops. The devices feature dual-bank flash memory for seamless firmware updates via FOTA, enabling continuous system operation in applications such as metering, where downtime must be minimised. The dual-bank architecture allows one memory bank to run the user program, while the other receives updates. This approach maintains system functionality throughout the process, enhancing reliability.

“The Renesas RL78 Family of 16-bit microcontrollers has been one of the most successful products since its launch more than ten years ago, particularly in home appliances,” said Daryl Khoo, vice president of Embedded Processing at Renesas. “I’m pleased to announce the RL78/L23, a new generation of RL78 microcontrollers with rich features, ideally suited for smart home appliances and cost-sensitive IoT solutions. With these devices, we aim to provide a better user experience with our intuitive development environment so that customers can get to production faster with confidence, based on market-proven Renesas technologies.”

The RL78/L23 comes with an easy-to-use development environment. Developers can leverage robust support tools such as Smart Configurator and QE for Capacitive Touch to streamline system design. Renesas offers the RL78/L23 Fast Prototyping Board, which is compatible with Arduino IDE, and a capacitive touch evaluation system for in-depth testing and validation.

The company offers Induction Heating Rice Cooker Solution, which combines the new RL78/L23 devices with numerous compatible devices from its portfolio to provide a wide array of Winning Combinations. Winning Combinations are technically vetted system architectures from mutually compatible devices that work together seamlessly to bring an optimised, low-risk design for faster time to market. Renesas offers more than 400 Winning Combinations, featuring a wide range of products from the Renesas portfolio, to enable customers to accelerate the design process and bring their products to market more quickly.

The RL78/L23 MCUs are available now, along with the Fast Prototyping Board (FPB-RL78L23) and the capacitive touch evaluation system (RSSK-RL78L23).