Low-power, high-performance MCUs include DSP & FPU

2nd July 2015
Barney Scott

Renesas has announced the development of the RX231 Group of 32-bit MCUs, which offers industrial and healthcare designers an optimal combination of high performance with DSP, FPU, and low power consumption. The RX231 Group suits applications that require high processing performance in environments with low current supply capacity, such as industrial sensors, healthcare, wearables and building automation devices such as thermostats.

With industrial sensors and healthcare devices, processing can be time consuming and inefficient. Batteries for these types of systems are designed to support low current supply capacity, but during signal measurement, they must handle high processing loads, such as eliminating noise from digital signals and performing floating-point calculations. As the current consumption cannot be increased, designers cannot boost the processing speed by raising the operating frequency of the CPU. The long processing durations cause increased power loss for the entire system.

The RX231 Group provides a combination of power-efficient MCU technology and the high-performance RXv2 CPU core with powerful DSP/FPU operation capabilities. It minimises current consumption and handles tasks involving heavy calculation loads such as digital filtering and floating-point operations considerably fast. This makes it possible to substantially reduce the power loss for the system as a whole during processing. For example, running the Renesas IIR digital filter consumes 10% less power and takes about half as long as was the case with earlier products.

In addition, current consumption during standby is only 0.8μA, approximately half the level of previous generations. With these top-class power performances, power efficiency is approximately doubled during intermittent operation, in which operating and standby states alternate. This allows extended operation on battery power.

The RXv2 CPU core achieves a performance benchmark score of 4.16CoreMark/MHz, 35% higher than the RX200 Series with the earlier RXv1 core. With operating speeds of 54MHz, and approximate two- to fourfold increases in DSP performance and a sixfold increase in FPU performance, the MCUs significantly reduce the time required for high-processing load tasks such as digital filtering.

The RX231 Group achieves industry-leading current consumption, only taking 0.8µA in standby mode, while retaining the contents of both SRAM and CPU registers, and consuming only 120µA/MHz when the CPU is active with peripherals off. The RX231 Group can recover from standby mode in a minimum of 5µs, which makes it possible to reduce current loss during the recovery and allow the application to react quickly to external events. Applications can be executed from flash after this time, and analogue functions, such as the ADC, are available for use.

The RX231 Group also supports an additional Low Power Timer (LPT), which consumes only an additional 0.4µA and allows the user to programme the device to wake up from the low power modes with a very wide range of possible timings, minimising current consumption in many different applications.

The RX231 Group provides proven capacitive touch sensor capabilities equipped with Renesas’ 2nd gen capacitive touch technology. With support for up to 24 touch keys for self-capacitance mode and up to 144 keys for mutual capacitance mode, the RX231 MCUs can support LED, buzzer, and communication functions in more basic touch systems such as blood pressure monitors (typically 9 keys), to systems with more elaborate requirements like security keypads (19 keys) and ovens (25 keys). This touch key functionality combines high sensitivity with a high level of noise tolerance, allowing use even when the panel is wet or when the operator is wearing gloves. This makes it possible to create highly flexible user interfaces in terms of usage environment and device design.

For smart home and building automation, industrial networking, and remote sensor networks, advanced connectivity and the ability to support multiple interface standards are critical. The RX231 Group fully supports emerging IoT platforms by providing enhanced communication functionality with complete USB 2.0 support, including device/host and OTG operation and full compliance to Battery Charging specification 2.0. The RX231 devices also feature several connectivity peripherals, including up to 7 SCI channels, SDHI support, a CAN interface with ISO 11898-1 compliance, and an IrDA interface for wireless connectivity and audio support.

Compliance with international safety standards is important in industrial automation, home appliance and electrical control applications. The RX231 MCUs offer extensive hardware-based safety features for UL and IEC60730, including self-diagnostic and disconnect-detection monitoring for the on-chip ADC; a clock frequency accuracy measurement circuit; an independent watchdog timer, and a built-in hardware memory test to spot anomalies in the internal RAM. For enhanced security, the RX231 provides AES encryption, a hardware-based Random Number Generator (RNG) and Unique Device ID that can be configured to support advanced cryptology requirements.

Samples of the RX231 Group are available now. Mass production of the RX231 Group is scheduled to begin in September 2015. (Availability is subject to change without notice.)

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