Based on the fast RX core, the new 32-bit MCUs are ideal for building high-performance inverter control systems for applications such as DC motor control in energy-efficient appliances like refrigerators, air conditioners, washing machines, vacuum cleaners, and fans; and entry-level to mid-range industrial equipment such as general-purpose drives, power tools, drones, and office equipment. Features are optimized for inverter drive control, including an on-chip floating-point unit (FPU) that reduces code size and development time by up to 30 percent.
Energy efficiency regulations have become stricter in many countries in recent years, expanding to include industrial equipment and household appliances from entry-level to mid-range. System designers in these price-competitive markets are seeking new approaches to achieve the lowest energy consumption within increasingly limited budget constraints for product cost and energy efficiency. The demand for more compact, efficient, and quieter motors in office equipment such as printers and multifunction devices has led to a shift away from stepper motors toward the adoption of brushless DC motors. There is a need for more precise position control without increasing system costs.
To meet market demands for improved energy efficiency, more precise control, and lower development costs, Renesas has developed the RX23T microcontrollers, which offer an excellent cost-performance ratio. These new MCUs provide an optimized subset of the functions of the RX62T group, which has a proven track record in inverter control, and are specifically designed for use in three-phase inverter drive applications.
Main features of the RX23T controllers:
1) High-precision inverter control and reduced development time for entry-level and mid-range devices.
Inverter control requires a large number of arithmetic operations involving decimal points, and it is useful to perform these using a floating-point arithmetic unit (FPU). However, cost constraints in mid-range and affordable energy-efficient household appliances and industrial equipment have prevented the use of expensive microcontrollers with on-chip FPUs. Instead, the most common approach has been to develop software for a fixed-point arithmetic unit. The new RX23T microcontrollers incorporate an on-chip FPU at no additional cost, eliminating the need to implement the decimal position switching required when using a fixed-point arithmetic unit. This simplifies software configuration and can reduce code size and development time by up to 30%. The on-chip peripheral functions are also optimized for individual inverter drives, enhancing the cost-performance ratio and making it possible to add high-precision inverter control to entry-level and mid-range products.
2) Industry-leading high power efficiency, even for lower power consumption in inverter products.
The RX23T MCUs feature the RXv2 core (4.55 CoreMark/MHz (target), among the best in the industry) and digital signal processing (DSP) functionality, allowing the operation process to maintain real-time responsiveness during inverter control (sensorless vector control), even when the CPU is not running at high speed. Furthermore, current consumption in low-power mode (data stored in RAM) is only 450 nA (typ.). This energy efficiency is among the best in the industry, enabling inverter products to have lower power consumption.
3) Support for 5V I/O peripherals makes it easier to implement measures to reduce the effects of electromagnetic noise from the inverter drive.
As systems become more efficient and supply voltages decrease, it becomes necessary to take measures to prevent electromagnetic noise from peripheral components that adversely affect high-precision control, since MCUs are more susceptible to such interference when the supply voltage is low. By supporting a 5V supply voltage, the new RX23T MCUs are less vulnerable to inverter drive noise than MCUs using a 3V power supply, thus reducing the number of components needed to mitigate the effects of noise.
