STMicroelectronics Boosts Design for a Cleaner Cloud with STM32 Digital-Power Microcontrollers

State-of-the-art feature integration in STM32F334, including high-resolution timer, brings high efficiency to digital power conversion

Geneva, June 25, 2014 - The Cloud supporting the digital economy could become significantly more energy-efficient with the adoption of the new Digital Power microcontrollers (STM32F334) from STMicroelectronics STM, a global semiconductor leader serving customers across the spectrum of electronics applications.

Today's digital infrastructure draws large quantities of electrical energy. Data centers alone are believed to consume around 1.3% of the world's electricity - about 264,000 GWh per year. Only about 40% of this energy is used productively, according to Power Usage Effectiveness (PUE) calculations by the Uptime Institute, while the rest is lost, mostly as heat that must be dissipated by large and expensive cooling systems. It is therefore vital to improve efficiency as the numbers of cloud users and uptake of cloud services are growing quickly and predicted to continue growing.

Techniques such as digital control of computer power supplies can help boost data-center efficiency to over 60% by adjusting continuously as power demand fluctuates, according to the Uptime Institute. ST's new microcontroller simplifies the data-center industry's transition to energy-efficient digital power supplies, such as multi-phase interleaved or resonant soft-switching (LLC), by providing all the major power-control functions in a single chip. The 217ps high-resolution timer embedded in the STM32F334 guarantees superior precision allowing better power-supply efficiency while the asynchronous ultra-fast reaction time guarantees safe operation. This will maximize the impact of digital power conversion to improve the Cloud's efficiency, potentially reducing global electricity demand by around 260GWh daily - equivalent to the electricity consumption of the Netherlands.

"Integrating features already proved in STM32 F3 devices used for digital motor drives and solar-inverters, the new STM32F334 Digital Power line adds innovations such as the high-resolution timer, making these the industry's most advanced microcontrollers for digital power applications," said Michel Buffa, General Manager, Microcontroller Division, STMicroelectronics. "With built-in high-speed peripherals featuring versatile interconnects, multiple timer outputs, powerful CPU and communication peripherals, these devices greatly simplify digital control of complex power-supply topologies used in data servers and telecom infrastructure, as well as in wireless charging points, lighting, welding, and industrial power supplies."

The new STM32F334 Digital Power line is an extension of ST's successful STM32 family. The full pin and SW compatibility with the entry-level STM32F301 devices (with the 7ns PWM resolution) provides the powerful advantage of a single development platform. A proven development ecosystem supports the STM32F334 Digital Power line, assisting the design of high-performance digital power units.

STM32F334 Digital-Power microcontrollers are in production now and available in LQFP64, LQFP48 or LQFP32 packages, priced from $1.54 for orders of 10,000 units.

Technical Notes to Editors:

The STM32F334 microcontrollers have ample computation capabilities thanks to the 72MHz ARM^® Cortex^®-M4 core with DSP and floating-point unit (FPU). The on-board Core-Coupled Memory (CCM-SRAM) provides a "routine boost" (90DMIPS equivalent to >100MHz CPU frequency), which accelerates the execution of control loop or any critical routine.

The high-resolution timer is based on a modular architecture providing 217ps (picosecond) resolution, guaranteed over voltage and temperature changes, and offers over 10 independent PWM outputs to control converters with a large number of switches or multiple converters in parallel. The guaranteed resolution of 217ps allows fine control of resonant soft-switching converters, which are becoming more widely used. For such LLC converters, the high resolution allows finer frequency and phase adjustments for improved voltage regulation and transient management. Controlling the 10 timer outputs is simple and flexible thanks to the internal crossbar. PWMs are optimized for control of power switches, with built-in shut-down capability, dead-time control, synchronization support, and safety features. The transparent high-resolution implementation simplifies programming: the timer is programmed similarly to a standard timer clocked at 4.6GHz.

Beside this high-resolution timer, the STM32F334's peripheral set optimized for digital power control includes:

• Two ultra-fast 5Msps (0.2µs) 12-bit ADCs with sampling time down to 21ns for simultaneous voltage and current measurements
• Three ultra-fast comparators with 25ns response time from analog input to PWM output, which helps ensure safe power-supply operation
• Three DACs (Digital Analog Converter) and one operational amplifier with built-in gains
• CAN, I²C (PMBus/SMBus)

In addition, the microcontrollers have flexible input and output circuitry that allows connection to any kind of driver or logic at the output and can accept internal or external fault signals on either analog or digital inputs.

The devices are fully supported by the latest version of STM32Cube software: STM32CubeMX initialization C-code generator with graphical user interface, which simplifies operation and set-up of the high-resolution timer, and the STM32CubeF3 embedded software library containing also the Hardware Abstraction Layer (HAL) for the STM32F334 peripherals and a set of middleware.

The boards related to the STM32F334 ecosystem and available now are:

·     Discovery kit (32F3348DISCOVERY) with on-board buck-boost converter;

·     500W Digital Switched-Mode Power Supply (DSMPS) evaluation board (STEVAL-ISA147V2) featuring a resonant LLC DC/DC converter and semi-bridgeless Power-Factor Correction (PFC);

·    The STM32Nucleo open platform (NUCLEO-F334R8).

A 'Cook Book' (AN4539) helps users operate the high-resolution timer in various basic power-supply topologies. Dedicated application notes for LED dimming and LLC control are also available.

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