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32bit ARM Cortex MCUs tout cost-competitive digital signal control

Posted: 29 Jun 2012 ?? ?Print Version ?Bookmark and Share

Keywords:ARM Cortex? MCU? STM32 family?

STMicroelectronics has rolled the first samples of its STM32 F3 series of MCUs to its OEM customers for the early evaluation of the product family which features an embedded ARM Cortex-M core.

Aside from the Cortex-M4 core, the SoC also features a floating-point unit (FPU). They are designed for handling and processing mixed signals in circuits such as three-phase motor controls, biometrics and industrial sensor outputs or audio filters.

They are expected to simplify design, lessen power consumption and shrink PCBs in consumer, medical, portable fitness, system monitoring and metering applications.

The series extends the scope of ST's STM32 family by allowing designers to tackle mixed-signal control applications. They feature analog circuitry and the ARM Cortex-M4 with FPU, providing low to medium memory sizes at competitive cost.

The Cortex-M4 with FPU core augments the proven Cortex-M3 CPU with additional DSP capability, optimizes single-cycle and saturating arithmetic instructions, and boosts performance over ST's STM32 F1 Cortex-M3 devices. It positions the new series between the company's STM32 F1 and the STM32 F4, which features the Cortex-M4 with FPU core and large memory capacity combined with high-speed 168MHz maximum CPU frequency for complex applications.

With the new F3 MCUs, ST's STM32 family now offers more than 350 variants addressing applications from entry-level, price-sensitive designs through to those demanding high performance and rich on-chip features. The new F3 series enables ST to deliver the advantages of its STM32 devices and ecosystem to applications that have formerly required both high-performance analog and an entry-level digital signal controller, such as high-performance motor control or embedded digital audio.

STM32 F3 series devices also incorporate ST's latest improvements to digital peripherals for its STM32 family, which Michel Buffa explains is a further advantage of the extensive compatibility between all ST's ARM Cortex-M MCUs.

Further technical information:

The STM32 F3 family featuring the ARM Cortex-M4 with FPU comprises four product lines, differentiated according to on-chip memory density and integrated peripherals. The peripherals deliver extreme analog integration, offering best-in-class performance through functions such a 12bit Analog-to-Digital Converter (ADC) offering 5Msamples per second performance. Extreme analog integration maximizes flexibility for designers to implement advanced system features and functions without adding extra components on the pc-board.

STM32 F30x devices have seven fast comparators with 50ns response time, four programmable gain amplifiers supporting four different gain settings with 1 percent accuracy, two 12bit DACs, and four 12bit 5MSps ADCs. This is the fastest ADC performance in any ARM Cortex-M MCU, achieving up to 18MSps in interleaved mode. The devices also have two advanced motor-control timers running at up to 144MHz. These allow one MCU to manage two motors plus power factor correction (PFC) via its on-chip analog peripherals, in equipment such as home appliances. Among other capabilities of the advanced timers, timing resolution better than 7ns allows new applications such as digital power supplies in telecom infrastructure or data servers, micro-inverters in solar installation and LED lighting to benefit from the scalability, low power consumption and cost-effective performance of the STM32 family.

To help developers optimize code execution time, the STM32 F30x devices have 8KB of SRAM mapped to the instruction bus as Core Coupled Memory (CCM-SRAM). Critical routines loaded in the 8KB CCM at startup can be completed at full speed with zero wait states, achieving 94 Dhrystone MIPS at 72MHz. This compares with 62 DMIPS when executing from Flash or SRAM; equivalent to a 52 percent performance increase for critical routines. The STM32 F30x series also has up to 40KB of SRAM mapped on the data bus. The 8K CCM-SRAM can also be used for data storage with no performance tradeoff. Devices are pin compatible with the STM32 F1 series, and also share the same API, which simplifies migration to higher performing devices.

Peripheral functions
The STM32 F37x devices deliver a different blend of peripheral functions. They are the first MCUs from ST to integrate a 16bit Sigma-Delta ADC on-chip, allowing the STM32 family to solve a wider range of precision-sensing applications and providing a single-chip solution capable of replacing a discrete general-purpose processor and separate ADC. Up to three 16bit Sigma-Delta ADCs are integrated on-chip, with separate analog supply from 2.2V to 3.6V, up to 21 single or 11 differential channels, and seven programmable gains per channel.

Other STM32 F37x analog peripherals include two fast comparators, three 12bit DACs, and one 12bit 1Msps ADC. There is also an enhanced consumer electronics control unit, making these devices ideal for consumer multimedia products. Compared to the STM32 F1 series, STM32 F37x devices provide a SoCsolution enabling developers to reduce BOM and simplify board designs.

Key common features of STM32 F30x/F37x:

  • SRAM and CCM-SRAM with parity bit for secure software data and code execution;
  • Memory Protection Unit (MPU);
  • Capacitive touch-sense capability (24 keys);
  • Support for both USB and CAN connectivity;
  • Communication peripherals: SPI 18Mb/s, I2C 1MHz (fast mode plus), USART 9Mb/s;
  • Sub-ppm trimmable RTC with HW calendar
  • Four low-power modes with 5?A STOP mode having waking-up capability from communication peripherals with fast startup time;
  • Debug mode: serial wire debug (SWD), JTAG interfaces, Cortex-M4 ETM
  • Power supplies: 2.0V to 3.6V or 1.8V8 percent (dedicated sales types)

Prices for the STM32 F30x series start from $2.54 for the STM32F302 with 128KB Flash in LQFP48 package up to $3.86 for the 256KB STM32F303 in LQFP100, for orders over 1000 pieces. The STM32 F37x starts from $2.24 for the STM32F372 in LQFP48 with 64KB, up to $3.69 for the STM32F373 LQFP100 with 256KB. Other pricing options for higher quantities are available on request.

Both series are sampling now, to lead customers, and are scheduled to enter full production in Q3 2012.

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