Peak ultra-low-power MCU benchmark scores for ST’s ARM-base STM32
STM32L4 is aimed at next-generation energy-conscious consumer, industrial, medical, and metering applications. The first two microcontrollers in the series, the STM32L476 and STM32L486, use the 80 MHz ARM Cortex-M4 core with DSP and floating-point unit (FPU). With the added advantage of the ST ART Accelerator, which allows zero-wait execution from Flash, the devices achieve up to 100 DMIPS at 100 µA/MHz active power consumption. Up to 1 MB of dual-bank Flash supports sophisticated applications and read-while-write capability in addition to 128 kB of SRAM.
STM32L4 microcontrollers use ST’s low-power technologies, including dynamic voltage scaling to balance power consumption with processing demand, smart architecture with FlexPowerControl, and seven power-management modes with sub-mode options. These include Stop, Standby, and Shutdown with current as low as 30 nA. ST’s Batch Acquisition Mode (BAM) allows efficient data exchange with communication peripherals while in low-power mode.
The new devices have scored 123 in the standardised EEMBC ULPBench tests that compare the efficiency of ultra-low-power microcontrollers, which ST says shows that you can get higher performance and larger memory without trading power consumption. The company adds that overall low power consumption, high performance and DSP capability of the Cortex-M4 core, smart analogue features, and extensive digital connectivity of the new STM32L4 series make these devices suitable for smart connected and Internet-of-Things (IoT) applications, as well as a wide variety of industrial, medical, and consumer products.
STM32L4 will be priced from $3.40 in the LQFP64 package (10,000).
next; further architecture details…
In addition to low-power technologies, the STM32L4 also has a smart architecture and peripherals to maximise efficiency and performance while ensuring low power consumption. Digital peripherals include USB OTG full speed with a dedicated supply that allows users to maintain USB communication even when the system is powered at 1.8V. There is also a Digital Filter for Sigma-Delta Modulators (DFSDM) peripheral for connecting external sigma-delta modulators or PDM (Pulse Density Modulation) microphones.
Analogue peripherals include three 12-bit/5 Msample/sec ADCs featuring smart operation that allows sample acquisition at low speed drawing only few tens of μA to limit maximum current, or at maximum speed so as to return quickly to ultra-low-power mode. The ADCs can provide up to 16-bit resolution with hardware oversampling. There is also a voltage-reference buffer that provides a reference for ADCs, DACs, or for external components through the VREF+ pin. In addition there are two 12-bit DACs with sample and hold capability, which can operate during the MCU’s deep power-saving modes when overall current is reduced to a few hundred nA. Other analogue peripherals include two ultra low-power comparators that draw as little as 300 nA, as well as two op-amps with external or internal feedback routing and Programmable Gain Amplifier (PGA) capability.
The STM32L4 smart architecture gives a further boost to performance and efficiency by enabling concurrent transfers between the core, DMA controllers, memories, and peripherals. FlexPowerControl is another aspect of the smart architecture that assists power-saving design by retaining I/O levels when the device is in low-power mode, keeping SRAM in standby, and managing independent power supplies for specific peripherals and I/Os.
The STM32L486 integrates a hardware cryptographic co-processor (AES 256-bit). Combined with other STM32L4 features such as an independent battery-backup domain and tamper inputs, this provides a strong platform for security-oriented applications such as smart meters.
For applications where heat dissipation is a challenge, such as when used in confined environments or high ambient temperatures, high-temperature grade devices specified up to 125°C are available.
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