原标题：ST STM32L476Gxx系列超低功耗MCU开发方案

　　ST公司的STM32L476Gxx系列是基于高性能ARM® Cortex®-M4 32位RISC内核的超低功耗微控制器(MCU),工作频率高达80MHz,具有嵌入高速存储器(闪存高达1MB,SRAM高达128KB)和灵活的外接存储器控制器(FSMC),Quad SPI闪存接口和各种增强的I/O和外设.此外,器件还有三个快速12位ADC,两个比较器,两个运放,两个DAC通路和一个基准电压缓冲器,低功耗RTC,两个通用32位计时器,两个16位PWM计时器,七个通用16位计时器以及两个低功耗16位计时器.本文介绍了STM32L476xx系列主要特性,框图,以及评估板STM32L476G-EVAL主要特性,框图,电路图,材料清单和PCB元件布局图.

　　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.

　　• 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)

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

　　STM32L476xx系列主要特性:

　　• 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 Stop 2 with RTC

　　– 100 μA/MHz run mode

　　– Batch acquisition mode (BAM)

　　– 4 μs wakeup from Stop mode

　　– Brown out reset (BOR) in all modes except shutdown

　　– 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/1.25DMIPS/MHz (Dhrystone 2.1), and DSP instructions

　　• 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

　　• 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: 2 x 16-bit advanced motor-control, 2 x 32-bit and 5 x 16-bit general purpose, 2x 16-bit basic, 2x low-power 16-bit timers (available in Stop mode), 2x watchdogs, SysTick timer

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

　　• 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)

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

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

　　– 2x operational amplifiers with built-in PGA

　　– 2x ultra-low-power comparators

　　• 18x communication interfaces

　　– USB OTG 2.0 full-speed, LPM and BCD

　　– 2x SAIs (serial audio interface)

　　– 3x I2C FM+(1 Mbit/s), SMBus/PMBus

　　– 6x USARTs (ISO 7816, LIN, IrDA, modem)

　　– 3x SPIs (4x SPIs with the Quad SPI)

　　– CAN (2.0B Active) and SDMMC interface

　　– SWPMI single wire protocol master I/F

　　• 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™

　　图1.STM32L476xx系列框图

　　评估板STM32L476G-EVAL

　　The STM32L476G-EVAL evaluation board is designed as complete demonstration and development platform for STMicroelectronics ARM® Cortex®-M4-core-based STM32L476ZGT6 microcontroller with three I²C buses, three SPI and six USART ports, CAN port, SWPMI, two SAI ports, 12-bit ADC, 12-bit DAC, LCD driver, internal 128-Kbyte SRAM and 1-Mbyte Flash memory, Quad-SPI port, touch sensing capability, USB OTG FS port, LCD controller, flexible memory controller (FMC), JTAG debug port. STM32L476G-EVAL can be used as reference design for user application development, although it is not considered as final application. A full range of hardware features on the board helps users evaluate all on-board peripherals such as USB, USART, digital microphones, ADC and DAC, dot-matrix TFT LCD, LCD glass module, IrDA, LDR, SRAM, NOR Flash memory device, Quad-SPI Flash memory device, microSD card, sigma-delta modulators, smartcard with SWP, CAN transceiver, EEPROM, RF-EEPROM. Extension headers allow connecting daughterboards or wrapping boards. ST-LINK/V2-1 in-circuit debugger and flashing facility is integrated on the mainboard.

　　图2.评估板STM32L476G-EVAL外形图

　　评估板STM32L476G-EVAL主要特性:

　　• STM32L476ZGT6 microcontroller with 1-Mbyte Flash memory and 128-Kbyte RAM

　　• four power supply options: power jack, ST-LINK/V2-1 USB connector, USB OTG FS connector, daughterboard

　　• microcontroller supply voltage: 3.3 V or range from 1.71 V to 3.6 V

　　• two MEMS digital microphones

　　• two stereo audio headphones jack outputs with independent audio content

　　• slot for microSD card supporting SD, SDHC, SDXC

　　• 4-Gbyte microSD card bundled

　　• 16-Mbit (1M x 16 bit) SRAM device

　　• 128-Mbit (8M x 16 bit) NOR Flash memory device

　　• 256-Mbit Quad-SPI Flash memory device with double transfer rate (DTR)support

　　• RF-EEPROM with I²C bus

　　• EEPROM supporting 1 MHz I²C-bus communication speed

　　• RS-232 port configurable for communication or MCU flashing

　　• IrDA transceiver

　　• USB OTG FS Micro-AB port

　　• CAN 2.0A/B-compliant port

　　• joystick with four-way controller and selector

　　• reset and wake-up / tamper buttons

　　• touch-sensing button

　　• light-dependent resistor (LDR)

　　• potentiometer

　　• coin battery cell for power backup

　　• LCD glass module daughterboard (MB979) with 40x8-segment LCD driven directly by STM32L476ZGT6

　　• 2.8-inch 320x240 dot-matrix color TFT LCD panel with resistive touchscreen

　　• smartcard connector and SWP support

　　• NFC transceiver connector

　　• connector for ADC input and DAC output

　　• power-metering demonstration with dual-channel sigma-delta modulator

　　• PT100 thermal sensor with dual-channel sigma-delta modulator

　　• MCU current consumption measurement circuit

　　• access to comparator and operational amplifier of STM32L476ZGT6

　　• extension connector for motor control module

　　• JTAG/SWD, ETM trace debug support, user interface through USB virtual COM port, embedded ST-LINK/V2-1 debug and flashing facility

　　• extension connector for daughterboard

　　图3.评估板STM32L476G-EVAL框图