New Industry Products

32-Bit MCUs Targeted to Sensorless Vector Motor Control

March 22, 2016 by Power Pulse1595211359

Renesas Electronics today at the IEEE Applied Power Electronics Show (APEC 2016) expanded its robust lineup of 32-bit microcontrollers (MCUs) with the RX24T Group. Using the RXv2 CPU core, the new MCUs deliver double the performance from the RX23T, 30 percent reduced development time, and features additional instructions designed to accelerate performance and improve energy efficiency in industrial equipment, office equipment, and household appliances.

The new product lineup comprises a total of six new devices with pin counts from 80- to 100-pin and on-chip flash memory capacities from 128kB to 256kB. The RX24T Group enables simultaneous inverter control of multiple motors with a single chip and are ideally suited for permanent magnet ac (PMAC) motor control in a variety of applications.

The RX24T Group offers up to 160 DMIPs, including dedicated analog functions to optimize the inverters Bill of Material (BoM) and furthermore increases the arithmetic operation and expands the motor-control peripheral functions of the cost-optimized RX23T. In addition, Renesas plans to deliver a 24 V motor control evaluation kit that can support both the single-motor control RX23T and the multi-motor control RX24T.

Recently many countries have imposed legal requirements mandating improved motor efficiency, in addition to regulations intended to reduce energy consumption. This has increased demand for highly efficient inverter control.

However, this has also created numerous concerns for system manufacturers who want to quickly release products for this new market but who lack the necessary development workforce and motor control expertise. In addition, many types of equipment are becoming more compact, reducing the amount of space available for printed circuit boards. Finding ways to reduce the number of components in order to integrate multiple boards and reduce their number has therefore become a major issue.

In response to this demand for better energy efficiency, higher-precision control, reduced board size, and shorter development time, Renesas has developed the RX24T Group, a high-speed, high-functionality 32-bit Group of MCUs that enables control of multiple motors with a single chip.

Key features of the new RX24T Group of MCUs: 1) With on-chip FPU functionality for faster code execution, RX24T supports high-performance multi-motor control for development of platforms with a broad range of products.

The RX24T incorporates the RXv2 CPU core with a five-stage pipeline, a floating point unit and DSP functions, executing 32-bit multiply within a single instruction to improve algorithm calculation accuracy. Effectively, the RX24T running at 80 MHz has similar performance levels of a comparable 100MHz MCU. The on-chip FPU functionality provides faster implementation of calculation-intensive algorithms with wide dynamic range.

The FPU enables the overall code to be reduced, and overall software implementations are executed much faster as no scaling or saturation occurred. It offers a higher accuracy than the integer implementation as the real physical units are used in the embedded software.

In addition, the FPU guarantees a faster computation time for PI controllers and estimators. The FPU simplifies debugging and can reduce development time by approximately 30 percent while reducing the rate of software glitches.

In addition, the RX24T Group of MCUs maintains excellent compatibility with the RX23T Group, allowing reuse of existing hardware and software assets, boosts CPU performance from 40 MHz to 80 MHz and Flash capacity from 128 KB to 256 KB, and doubles the power of the on-chip motor control–related peripheral functions (timers, A/D converters, and operational amplifiers) to enable control of multiple Permanent Magnet AC motors using a single chip. The RX24T also integrates fail-safe mechanisms in hardware enabling fast implementation and execution of Class B Self-Test routines, mandatory for the IEC60730-1 safety compliance.

2) Renesas’ flexible motor control development solution and tools allow one-day evaluation of sensorless vector control

Developing new motor-enabled systems for a rapidly growing market demands short application development cycles and specialized expertise. Renesas has developed a flexible 24 V motor control evaluation kit for use with the RX23T and RX24T. It enables developers to start evaluating motor control applications quickly, allowing development work to get underway with less effort. The kit includes a CPU card, a low-voltage inverter, a PMAC motor with sensorless vector control driver software, and sample demos.

The kit also includes an in-circuit scope (ICS), a RAM variable waveform display tool that is indispensable in reducing the development workload, provides safe debugging and substantially shortens the time needed for evaluation. An intuitive auto tuning tool lets users tune their own motor in less than a minute, significantly simplifying development and eliminating typical trial-and-error methods. Software and evaluation tools include support for CS+ and e2 studio integrated development environments, a code generation support tool, C compilers, debuggers, and flash memory programmers.

In addition, the RX24T Starter Kit will also be available to provide a complete development environment for initial implementation, including a reference board populated with the RX24T and an MCU evaluation environment.

3) Fewer external components for smaller printed circuit boards

As applications become more compact, print circuit boards sizes have shrunk, resulting in strong demand for MCUs that integrate the functions of external components. The RX24T integrates on-chip external circuits required by inverter control systems, such as op-amps supporting simultaneous four-channel amplification of three-shunt and one-shunt currents, comparators capable of overcurrent detection of amplified current, sample and hold circuits that can handle up to five channels simultaneously, such as three-shunt currents, and DataFlash for storing log and setting files. This dramatically reduces the mounting area needed on the PCBs. The RX24T and RX23T also incorporates an automatic pwm signals shutdown to ensure the protection of the three-phase bridges; the module is called Port Output Enable (POE) and set the signals in high impedance state to secure the inverter.