MCUs power-down to 0.4 µA, use ARM cortex M0+ core

February 12, 2014 // By Graham Prophet
STMicroelectronics’ STM32 ultra-low-power microcontrollers are aimed at extending battery life in consumer, health, and industrial applications. They are built around a 32MHz ARM Cortex M0+ processor core, a 12-bit ADC that ST says sets a new standard for low power consumption, plus a USB FS 2.0 crystal-less solution.

The ADC uses 40 µA at a conversion speed of 100 ksamples/sec, rising to 200 µA at 1.14 Msamples/sec; in combination with the outstanding power efficiency of both the processor core and the ultra-low-power peripherals, applications such as fitness trackers and domestic smoke detectors powered by non-rechargeable batteries will require less frequent replacements. For example, ST calculates that an STM32L0-based fitness tracker powered by a non-rechargeable coin-cell battery could operate for up to two years before needing a new battery.

The MCUs are fabricated in ST’s CMOS technology that offers both embedded EEPROM, as well as the smallest variation in power consumption over the 25°C - 125°C temperature range, leading to record low consumption levels at elevated temperatures. This suits the MCUs to (distributed) industrial sensor applications relying on batteries or energy harvesting.

The STM32L0 series is offered in three lines: Access line, USB line, and USB/LCD line. Common features of all of the new devices include power consumption in several modes including 139 µA/MHz @ 32MHz, 87 µA/MHz using an optimised mode, and 400 nA in Stop mode with full RAM retention and a 3.5 µsec wake-up time. The series also features up to 64 kB of Flash memory, up to 8 kB of SRAM, and 2 kB of embedded true EEPROM. A built-in hardware oversampling capability also enables 16-bit ADC resolution. STM32L0 devices with integrated USB FS 2.0 interface support battery charger detection and link power management. Crystal-less operation of the USB is enabled via a built-in 48 MHz oscillator. All the lines offer built- in hardware engine encryption (AES) as an option.

The devices are pin-to-pin compatible with STM32L1 or any other STM32 devices, enabling you to upgrade designs to take advantage of the new power-saving opportunities. In UQFN32 (5 x 5 mm), LQFP32 (7 x 7 mm), LQFP48 (7 x 7 mm), LQFP64 (10 x 10 mm), and BGA64 (5 x 5 mm) packages, the devices