SoCs Target Motor Control

The microcontroller market is marked by a continuing integration, generally referred to as system on chip (SoC), that brings together a lot of features to address particular application areas.

Companies like Freescale and TI produce a number of lines that fit this category. These devices usually include a processor core, memory, I/O, and tools to convert signals from digital to analog and back.

The most common CPU core used in these devices is the Advanced Risk Machines (ARM) Core. This CPU design traces back to the Acorn computer developed in the UK in the 1980s. Over the years, ARM has developed a number of architectures based on that design, including a microcontroller targeted series (used in a number of control applications) and an application processor targeted series (often used in cellphones and tablets).

One salient feature of these devices is their approach to low-power operation. The ARM processor architecture defines a number of power levels. At each level, portions of the chip are powered down. Many implementers provide a more finely graduated set of power levels, giving the programmer an unprecedented level of control over power consumption.

The STMicroelectronics STM32 microcontroller line includes more than 350 part numbers with pin counts ranging from 20 to 176. These devices offer a number of processor speed, memory, and functional unit combinations. The STM32 F3 series is targeted at the controller market. One of the important application areas it addresses is motor control. In addition to the ARM Core, the SoC includes analog-to-digital converters, digital-to-analog converters, comparators, and two dedicated motor control timers. This allows the system to control two motors simultaneously using current and other sensors. Using the onboard digital signal processing (DSP) functions of the ARM processor, complex control loops can be developed quickly and compactly.

The other interesting thing is that this is a full 32-bit processor, with floating point and DSP instructions that operate at clock speed. STMicroelectronics also provides motor control software that can be customized to use as a starting point.

The STM32F3 is another option for motor control from STMicroelectronics. So is the cSPIN line, which we discussed in December. The cSPIN line is a dedicated part, while the STM32F3 can combine other functions with motor control. These are good examples of the flexibility and processing power that can be brought to bear in industrial control applications.

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