Renesas RA0E1 MCU Eases the Price-Versus-Performance Design Challenge

“Green light” approval and the success of electronic applications can come down to a matter of pennies. That's why engineers choosing the right microcontroller unit (MCU) often face the excruciating challenge of balancing performance and price. Renesas Electronics Corporation aims to make that choice easier with an ultra-low-power Arm®-based MCU aimed at cost-sensitive embedded applications.

It's difficult to overestimate the pressure on engineers to develop power-efficient, low-cost applications. Competitive issues, consumer and business customer expectations, and the rapid pace of innovation increase the odds that even a slight miscalculation on the costs of the finished product or the performance of the MCU could undermine success.

An MCU is just one component, but it is critically important in scoping out overall systems costs. Consider that a price differential of 50 cents per unit could add up to an additional $50,000 for a planned production run of 100,000 end products.

That may be just the tip of the iceberg: In addition to the actual per-unit cost of the MCU, developers must factor in a variety of potential hidden-cost factors that can impact project budgets, such as:

• Licensing fees for software tools and development environments
• Training time
• Testing and troubleshooting
• Need for peripheral components
• Firmware creation
• Power management
• Compliance and certification

Even for much smaller production runs, where the MCU price differential may not add up to a large amount, the related additional costs often will be relatively more expensive due to amortization over a smaller number of production units. That could make project approval a non-starter.

Power consumption and thermal management can complicate the selection of the right MCU.

The more power the MCU consumes, the more likely the designer will need to accommodate additional components and possibly more costly batteries for mobile and portable applications. Similarly, the greater the power consumption, the more heat will be generated, perhaps requiring additional cooling techniques.

Nobody wants to overpay for components that deliver more performance than needed. But, neither do they want to create an application that underperforms when it's deployed. That's why achieving the optimal balance between cost and performance can make or break an application's success.

Achieving the optimal balance

The choice of MCU obviously must meet the specific features and functionality requirements of the planned application. But it also needs to fit within the desired budget, particularly when it comes to a price-sensitive application. That requires finding the optimal blend of performance, power consumption, and integrated peripherals.

Some applications are more price-sensitive than others. IoT devices for the home, for example, often face intense competitive pricing pressure, reflecting consumer expectations for lower-cost devices. Industrial automation applications generally require more robust and highly reliable devices for often unattended use, but still are most likely competing on price and other considerations.

Finding the right balance between price and performance begins with selecting the right MCU that meets performance requirements, is power-efficient, and provides flexibility for application designers.

Typically, higher-performance applications deliver more processing power, higher clock speeds, and the ability to accomplish more complex tasks. These more expensive MCUs typically incorporate several integrated peripherals, reducing the need for added components, although often with higher expenses for software development and debugging.

MCUs designed for cost-sensitive applications often come with the burden of fewer integrated peripherals, limited memory, and reduced design flexibility. However, they offer the benefit of reduced power consumption and extended battery life.

Renesas offers feature-rich MCUs for price-sensitive applications

Aiming to simplify the selection process for low-cost applications, Renesas offers the RA0E1 group, a feature-rich MCU with extremely low power consumption and optimized peripherals, which provides developers a way to enhance their designs for a reduced bill of materials.

Built with an energy-efficient Arm Cortex-M23 core and an impressive set of integrated timers, serial communications, analog functions, and security and safety functions, the RA0E1 MCUs are aimed directly at the market for cost-sensitive applications.

The Arm Cortex-M23 was designed as an entry-level 32-bit processor for energy-efficient operation. With a simple architecture that is easy to learn and program, this MPU core incorporates Arm's TrustZone security technology, debug and trace features to diagnose and optimize applications, and support for energy-efficient low-power modes.

The RA0E1 consumes 84.3 μA/MHz of current in active mode and 0.82 mA in sleep mode, making it highly suited for battery-powered and energy-sensitive applications. Its feature set provides versatility and efficiency for diverse applications, including consumer electronics, industrial automation, secure IoT devices, building automation, and small appliances.

With a supply voltage ranging from 1.6 V to 5.5 V, designers can utilize the RA0E1 without having to employ a level shifter or voltage regulator in 5 V systems. The RA0E1 also incorporates a high-precision on-chip oscillator, allowing designers to avoid having to add a standalone oscillator to their designs. Its oscillator improves baud rate accuracy and maintains ±1.0% precision in environments ranging from -40°C to +105°C.

MCUs that combine multiple functions into a single chip can drastically reduce the need for additional components. This integration simplifies the design, reduces the PCB footprint, and ultimately lowers the overall system cost. To help minimize external peripherals, the RA0E1 integrates numerous components, including:

• Up to 64 KB of integrated code flash memory and 12 KB of high-speed SRAM with a parity bit
• Analog peripherals, including a 12-bit ADC, a temperature sensor, and an internal reference voltage
• Communications peripherals, including 3 UART interfaces, 1 async UART interface, 3 simplified serial peripheral interfaces (SPIs), 1 inter-integrated circuit (IIC), and 3 simplified IICs
• Safety features, including SRAM parity check, invalid memory access detection, frequency detection, A/D test, immutable storage, a CRC calculator, and register write protection
• Security features including a unique ID, a true random number generator (TRNG), and flash read protection

The development environment and upward compatibility

Renesas offers developers a common design environment, the Flexible Software Package, that includes production-ready drivers, Azure RTOS, FreeRTOS, and other middleware stacks. It also provides developers with a pathway to migrate their applications to more powerful RA MCUs.

Arm cores feature a high degree of compatibility. The Cortex-M23 utilizes the Armv8-M instruction set, which is compatible with instruction sets used by other Cortex-M core architectures.

The Renesas RA01E MCUs are pin and peripheral-compatible with the Renesas RA2E1 line of MCUs, which are built around a 48 MHz Arm Cortex-M23 core that incorporates up to 128 KB of code flash and 16 KB SRAM. This provides the ability to upgrade designs built on the RA0E1 to higher-performance MCUs.

Renesas also offers the FPB-RA0E1 Fast Prototyping Board (Figure 1) for evaluating, prototyping, and developing RA0E1 MCU-based applications.

Figure 1: The FPB-RA0E1 board for prototyping RA0E1 microcontroller applications. (Image source: Renesas)

The evaluation board includes an Arduino UNO R3 interface and two Pmod connectors. Additionally, developers can take advantage of a built-in SEGGER J-Link™ emulator circuit that enables writing and debugging programs without needing additional tools.

Conclusion

The Renesas RA01E MCU provides an impressive set of features and integrated peripherals for developing ultra-low-power, cost-sensitive applications without compromising on price versus performance. It comes with multiple connectivity options and an available rich ecosystem with a comprehensive development environment that can aid the creation of applications with reduced bill of materials costs and provide a pathway to later migrate applications to more powerful devices.