16 May 12

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Many digital power control applications operate by using complex digital signal processing algorithms in dedicated processing devices, such as FPGA’s or DSP processors, that are designed to perform only one particular function. Microcontrollers haven’t been used in these instances because they weren’t able to continually process large amounts of data simultaneously from several input sources. Each input source would contain a digital data field that may at some specified width, such as 8, 16, or 32 bits.

These applications are usually designed to process this data at the highest possible speed and resolution while meeting certain power consumption and cost requirements.

Engineers are limited in their choice of a processing unit, as there are usually very few devices available that would perform the intended function. And once a choice is made, the device would only perform the one function it is designed for, and offers very limited flexibility.

Because of the complexity of the design, the costs almost always turn out to be much greater than the cost needed to implement a standard microcontroller into their design. The main reason for the increase in cost is that each dedicated processing unit needs specific software and other development tools that are unique to the particular device.

A general purpose MCU would have the advantage of having a standard software development tool that could be used over and over for other applications.

Renesas Electronics Corporation has taken a step in providing a possible solution to this problem with the new 32bit RX62G group, which is an extension of its RX600 microcontroller family.

These MCUs provide a unique combination of advanced analog features, processing power, high resolution capability and integrated timer functions. These features make the new RX62G MCUs ideal to implement high-accuracy digital control for a variety of digital power control applications, including motor control with power factor correction, power management, digital power supply, uninterrupted power supplies, and inverters/converters.

The new MCU enables complex algorithms to be implemented for processing data, along with precision control outputs at high resolution.

This can now be done at an affordable cost with standard software development tools, and enables much higher efficiency in digital power control applications. The RX62G group, which is based on high performance 32bit RX CPU core, comes with a comprehensive support ecosystem that provides a robust platform for digital power control applications. Renesas claims the RX62G group is the industry's first group of general purpose MCUs to provide this level of combined high resolution and extreme performance capability.

The new MCUs operate at 100MHz to achieve 165 Dhrystone MIPS (DMIPS) performance, and provide maximum power efficiency when operated at lower speeds while delivering high performance at higher speed. Integrated DSP functionality and floating point unit (FPU) enable efficient implementation of complex algorithms and control loops. The single-precision FPU runs separately from the RX62G CPU and simplifies decimal-point calculations, which can boost overall processing performance and simplify firmware development. With an embedded flash that works at CPU speed with no wait state, the RX62G delivers a real-time performance 165DMips at 100MHz in a pure deterministic manner.

The new series or processors feature four high-resolution timers capable of generating PWM signals with the high resolution (312.5psec) needed to control power bridges, inverters, or converters with maximum efficiency and lower power losses. When the high accuracy control is used for controlling digital power supplies in applications like servers or general power supply systems, high efficiency power management is possible.

Similar to the RX62T MCUs, the RX62G devices feature two 12-bit A/D converters and one 10-bit A/D converter unit that can capture analog input values from up to 20 channels at a minimum conversion time of 1 second. Each of the A/D converters can be triggered by timer units and can sample three phases in parallel. The RX62G MCUs also integrate a new 16-bit general-purpose pulse-width-modulation timer (GPT), and MTU3 multifunction timer-pulse units specialized for motor control. With this combination, one RX62G MCU can control up to three 3-phase motors simultaneously.

These new MCUs expand on the advanced analog and control features of the RX62T and RX63T devices, but provides enhanced performance and more efficient power consumption. The safety functions and peripheral functions of the RX62G group are upward compatible with those of the RX62T group. The safety functions enable fail-safe control for devices which use the RX62G group. The RX62G is also pin-compatible with the RX62T series, and software compatible with other members of the RX600 family. This offers better scalability options for changing design requirements for on a variety of different applications.