Power efficiency and digital filtering uprated in Renesas’ RX231 MCUs

July 01, 2015 // By Graham Prophet
With target application spaces such as industrial sensor and healthcare, this release of microcontrollers from Renesas offers a combination of the RXv2 CPU core with improved DSP/FPU and low-power consumption technology

The RX231 group of 32-bit microcontrollers (MCUs) addresses applications that require high processing performance in environments with low current supply capacity, such as industrial sensors, healthcare devices, and wearable devices, and building automation devices such as thermostats.

The RXv2 CPU core achieves a performance benchmark score of 4.16 CoreMark/MHz, 35% higher than the RX200 Series with the earlier RXv1 core. Operating speed is 54 MHz, and approximate increases of 2-4x in DSP performance and 6x in FPU (floating point) performance are claimed. The RX231 Group uses 0.8 µA in standby mode, while retaining the contents of both SRAM and CPU registers, and consuming only 120 µA/MHz when the CPU is active with peripherals off. RX231 Group MCUs can recover from standby mode in a minimum of 5 µsec, 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. The RX231 Group also supports an additional low power timer (LPT), which consumes only an additional 0.4 µA and allows the user to program the device to wake up from the low power modes with a very wide range of possible timings, minimising current consumption.

The RX231 Group provides capacitive touch sensor capabilities equipped with Renesas’ second-generation 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 such as 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.

The MCUs have complete