原标题：ST STM32L476VGT6超低功耗ARM MCU开发方案

　　ST公司的stm32L476VGT6是基于高性能Arm® Cortex®-M4 32位RISC核的超低功耗mcu,工作频率高达80MHz,具有单精度浮点单元(FPU),支持所有ARM单精度数据处理指令和数据类型,还能执行全套DSP指令和存储器保护单元(MPU),从而增加了应用安全性;具有100DMIPS性能,集成了多达1MB闪存以及128 KB SRAM,USB OTG FS,LCD,DFSDM.主要用在各种低功耗的应用.本文介绍了STM32L476VGT6主要特性,功能框图,电源框图和时钟树,以及 STM32L476 Discovery kit 32L476GDISCOVERY主要特性,框图,电路图以及PCB布局图和尺寸图.

　　The STM32L476xx devices are the ultra-low-power microcontrollers based on the high-performance Arm® Cortex®-M4 32-bit RISC core operating at a frequency of up to 80 MHz. The Cortex-M4 core features a Floating point unit (FPU) single precision which supports all Arm® single-precision data-processing instructions and data types. It also implements a full set of DSP instructions and a memory protection unit (MPU) which enhances application security.

　　The STM32L476xx devices embed high-speed memories (Flash memory up to 1 Mbyte, up to 128 Kbyte of SRAM), a flexible external memory controller (FSMC) for static memories (for devices with packages of 100 pins and more), a Quad SPI flash memories interface (available on all packages) and an extensive range of enhanced I/Os and peripherals connected to two APB buses, two AHB buses and a 32-bit multi-AHB bus matrix.

　　The STM32L476xx devices embed several protection mechanisms for embedded Flash memory and SRAM: readout protection, write protection, proprietary code readout protection and Firewall.

　　The devices offer up to three fast 12-bit ADCs (5 Msps), two comparators, two operational amplifiers, two DAC channels, an internal voltage reference buffer, a low-power RTC, two general-purpose 32-bit timer, two 16-bit PWM timers dedicated to motor control, seven general-purpose 16-bit timers, and two 16-bit low-power timers. The devices support four digital filters for external sigma delta modulators (DFSDM).

　　In addition, up to 24 capacitive sensing channels are available. The devices also embed an integrated LCD driver 8x40 or 4x44, with internal step-up converter.They also feature standard and advanced communication interfaces.

　　The STM32L476xx operates in the -40 to +85℃ (+105℃ junction), -40 to +105 ℃ (+125℃ junction) and -40 to +125℃ (+130℃ junction) temperature ranges from a 1.71 to 3.6 V VDD power supply when using internal LDO regulator and a 1.05 to 1.32V VDD12 power supply when using external SMPS supply. A comprehensive set of power-saving modes allows the design of low-power applications.

　　Some independent power supplies are supported: analog independent supply input for ADC, DAC, OPAMPs and comparators, 3.3 V dedicated supply input for USB and up to 14 I/Os can be supplied independently down to 1.08V. A VBAT input allows to backup the RTC and backup registers. Dedicated VDD12 power supplies can be used to bypass the internal LDO regulator when connected to an external SMPS.

　　The STM32L476xx family offers six packages from 64-pin to 144-pin packages.

　　• Three I2Cs

　　• Three SPIs

　　• Three USARTs, two UARTs and one Low-Power UART.

　　• Two SAIs (Serial Audio Interfaces)

　　• One SDMMC

　　• One CAN

　　• One USB OTG full-speed

　　• One SWPMI (Single Wire Protocol Master Interface)

　　STM32L476VGT6主要特性:

　　• Ultra-low-power with FlexPowerControl

　　– 1.71 V to 3.6 V power supply

　　– -40℃ to 85/105/125℃ temperature range

　　– 300 nA in VBAT mode: supply for RTC and 32x32-bit backup registers

　　– 30 nA Shutdown mode (5 wakeup pins)

　　– 120 nA Standby mode (5 wakeup pins)

　　– 420 nA Standby mode with RTC

　　– 1.1 μA Stop 2 mode, 1.4 μA with RTC

　　– 100 μA/MHz run mode (LDO Mode)

　　– 39 μA/MHz run mode (@3.3 V SMPS Mode)

　　– Batch acquisition mode (BAM)

　　– 4 μs wakeup from Stop mode

　　– Brown out reset (BOR)

　　– Interconnect matrix

　　• Core: Arm® 32-bit Cortex®-M4 CPU with FPU, Adaptive real-time accelerator (ART Accelerator™) allowing 0-wait-state execution from Flash memory, frequency up to 80 MHz, MPU, 100DMIPS and DSP instructions

　　• Performance benchmark

　　– 1.25 DMIPS/MHz (Drystone 2.1)

　　– 273.55 CoreMark® (3.42 CoreMark/MHz @ 80 MHz)

　　• Energy benchmark

　　– 294 ULPMark™ CP score

　　– 106 ULPMark™ PP score

　　• Clock Sources

　　– 4 to 48 MHz crystal oscillator

　　– 32 kHz crystal oscillator for RTC (LSE)

　　– Internal 16 MHz factory-trimmed RC (±1%)

　　– Internal low-power 32 kHz RC (±5%)

　　– Internal multispeed 100 kHz to 48 MHz oscillator, auto-trimmed by LSE (better than ±0.25 % accuracy)

　　– 3 PLLs for system clock, USB, audio, ADC

　　• Up to 114 fast I/Os, most 5 V-tolerant, up to 14 I/Os with independent supply down to 1.08 V

　　• RTC with HW calendar, alarms and calibration

　　• LCD 8× 40 or 4× 44 with step-up converter

　　• Up to 24 capacitive sensing channels: support touchkey, linear and rotary touch sensors • 16x timers: 2x 16-bit advanced motor-control, 2x 32-bit and 5x 16-bit general purpose, 2x 16- bit basic, 2x low-power 16-bit timers (available in Stop mode), 2x watchdogs, SysTick timer

　　• Memories

　　– Up to 1 MB Flash, 2 banks read-while-write, proprietary code readout protection

　　– Up to 128 KB of SRAM including 32 KB with hardware parity check

　　– External memory interface for static memories supporting SRAM, PSRAM, NOR and NAND memories

　　– Quad SPI memory interface

　　• 4x digital filters for sigma delta modulator

　　• Rich analog peripherals (independent supply)

　　– 3x 12-bit ADC 5 Msps, up to 16-bit with hardware oversampling, 200 μA/Msps

　　– 2x 12-bit DAC output channels, low-power sample and hold

　　– 2x operational amplifiers with built-in PGA

　　– 2x ultra-low-power comparators

　　• 20x communication interfaces

　　– USB OTG 2.0 full-speed, LPM and BCD

　　– 2x SAIs (serial audio interface)

　　– 3x I2C FM+(1 Mbit/s), SMBus/PMBus

　　– 5x USARTs (ISO 7816, LIN, IrDA, modem)

　　– 1x LPUART (Stop 2 wake-up)

　　– 3x SPIs (and 1x Quad SPI)

　　– CAN (2.0B Active) and SDMMC interface

　　– SWPMI single wire protocol master I/F

　　– IRTIM (Infrared interface)

　　• 14-channel DMA controller

　　• True random number generator

　　• CRC calculation unit, 96-bit unique ID

　　• Development support: serial wire debug (SWD), JTAG, Embedded Trace Macrocell™

　　• All packages are ECOPACK2® compliant

　　图1.STM32L476VGT6框图

　　图2. STM32L476VGT6电源框图

　　图3. STM32L476VGT6时钟树

　　STM32L476 Discovery kit (32L476GDISCOVERY)

　　The STM32L476 Discovery kit (32L476GDISCOVERY) helps the user to discover the STM32L4 ultra-low-power features and to develop and share applications.

　　It is based on the STM32L476VGT6 microcontroller with three I2Cs, three SPIs, six USARTs, CAN, SWPMI, two SAIs, 12-bit ADCs, 12-bit DAC, LCD driver, internal 128 Kbytes of SRAM and 1 Mbyte of Flash memory, Quad-SPI, touch sensing, USB OTG FS, LCD controller, FMC, JTAG debugging support.

　　The 32L476GDISCOVERY includes an ST-LINK/V2-1 embedded debugging tool interface, LCD (24 segments, 4 commons), LEDs, push-button, joystick, USB OTG FS, audio DAC, MEMS (microphone, 3-axis gyroscope, 6-axis compass), Quad-SPI Flash memory, embedded ammeter measuring STM32 consumption in low-power mode.

　　External boards can be connected through the extension and probing connectors.

　　图4.Discovery kit 32L476GDISCOVERY外形图

　　Discovery kit 32L476GDISCOVERY主要特性:

　　• STM32L476VGT6 microcontroller featuring 1 Mbyte of Flash memory and 128 Kbytes of RAM in LQFP100 package

　　• On-board ST-LINK/V2-1 supporting USB reenumeration capability

　　• Three different interfaces supported on USB:

　　– Virtual Com Port

　　– Mass storage

　　– Debug port

　　• Arm® Mbed enabled™(a) (see http: //mbed.org)

　　• LCD 24 segments, 4 commons in DIP 28 package

　　• Seven LEDs:

　　– LD1 (red/green) for ST-LINK/V2-1 USB communication

　　– LD2 (red) for 3.3 V power on

　　– LD3 overcurrent (red)

　　– LD4 (red), LD5 (green) two user LEDs

　　– LD6 (green), LD7 (red) USB OTG FS LEDs

　　• Push-button (reset)

　　• Four-direction joystick with selection

　　• USB OTG FS with Micro-AB connector

　　• SAI Audio DAC, stereo with output jack

　　• Digital microphone MEMS

　　• Accelerometer and magnetometer MEMS

　　• Gyroscope MEMS

　　• 128-Mbit Quad-SPI Flash memory

　　• STM32 current ammeter with 4 ranges and auto calibration

　　• I2C extension connector for external board

　　• Four power supply options:

　　– ST-LINK/V2-1

　　– USB FS connector

　　– External 5V

　　– CR2032 battery (not provided)

　　• Extension connectors

　　• Comprehensive free software including a variety of examples, part of STM32Cube™ package

　　图5. Discovery kit 32L476GDISCOVERY硬件框图

　　The new features supported on ST-LINK/V2-1 are:

　　These features are no more supported on ST-LINK/V2-1:

　　• USB software re-enumeration

　　• Virtual Com Port interface on USB

　　• Mass storage interface on USB

　　• USB power management request for more than 100mA power on USB

　　• SWIM interface

　　• Application voltage lower than 3 V