ATMEGA644A-MUR - 8-bit AVR MCU 64KB Flash 20MHz | Microchip
MPN： ATMEGA644A-MUR ✓ 啟用中ATMEGA644A-MUR 概覽
An 8-bit AVR microcontroller is a Harvard-architecture processor that separates program and data memory, pairing an enhanced RISC CPU core with on-chip flash, SRAM, and EEPROM. Within the embedded systems hierarchy, the ATmega family sits in the mid-range 8-bit microcontroller tier below 32-bit ARM devices, serving as the complete system-on-chip for cost- and power-sensitive control applications.
Key features of the ATMEGA644A-MUR include 64 KB ISP flash with read-while-write capability for self-programming and firmware updates in the field, 32 general purpose I/O lines with internal pull-ups, two flexible USARTs for multi-channel serial communication, a byte-oriented 2-wire (TWI/I2C) interface, an SPI serial port, and three flexible timers/counters with compare modes and PWM channels. A real-time counter supports RTC functions, and JTAG-based on-chip debugging simplifies development.
Architecturally, the ATmega644A is a member of the ATmega164A/PA/324A/PA/644A/PA/1284/P family, sharing a common core, peripheral set, and pinout across flash densities. The enhanced RISC core uses 32 general purpose working registers directly connected to the ALU, allowing one register and one memory operand to be processed in a single instruction. The device operates over an industrial temperature range and supports supply options across 2.5V, 3.3V, and 5V rails per distributor listings.
Typical applications include industrial automation controllers, building and home automation nodes, motor control and battery management systems, embedded instrumentation, and legacy AVR design maintenance. The 64 KB flash and 4 KB SRAM provide headroom for communication stacks such as Modbus or lightweight TCP implementations that smaller ATmega328 devices cannot host.
When designing with this device, note that Microchip application note AVR536 documents reduced low-frequency crystal oscillator drive strength versus the earlier ATmega644, so crystal load capacitance and ESR must be verified during migration. Decouple AVCC separately and place 100 nF ceramics at each supply pin.
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes not found in the manufacturer datasheet.
直接替換替代品，適用於 ATMEGA644A-MUR — 相同封裝，腳位對腳位相容。需重新設計 PCB 的不同封裝零件不列入。
此系列的變體
與下列產品可直接替換的同系列型號： ATMEGA644A-MUR （相同外形與佔位） — 差異在於 Package, EEPROM, SRAM, Core Architecture, Flash Memory.
ATMEGA644A-MU
✅ 直接替換📋 參考替代品（不在目錄中）
ATMEGA644PA-MUR
✅ 直接替換 ⚠️ 規格未經驗證📋 參考替代品（不在目錄中）
ATMEGA644P-20MUR
✅ 直接替換 ⚠️ 規格未經驗證📋 參考替代品（不在目錄中）
ATMEGA1284P-MUR
✅ 直接替換 ⚠️ 規格未經驗證聯絡詢價
查看資料表 →ATMEGA324PA-MUR
✅ 直接替換 ⚠️ 規格未經驗證📋 參考替代品（不在目錄中）
ATMEGA164PA-MU
✅ 直接替換聯絡詢價
查看資料表 →ATMEGA164A-MU
✅ 直接替換聯絡詢價
查看資料表 →ATMEGA644A-MUR 最大額定值與電氣特性
| Core Architecture | AVR enhanced RISC, 8-bit |
| Flash Memory | 64 KB (32K x 16) ISP Flash with read-while-write |
| SRAM | 4 KB |
| EEPROM | 2 KB |
| 最大時脈頻率 | 20 MHz |
| CPU Throughput | Up to 20 MIPS at 20 MHz (1 MIPS per MHz) |
| General Purpose I/O | 32 I/O lines |
| Working Registers | 32 x 8-bit general purpose |
| USART Channels | 2 |
| Timers/Counters | 3 flexible timers with compare modes and PWM |
| Serial Interfaces | TWI (I2C-compatible), SPI, 2x USART |
| Real-Time Counter | Yes |
| 封裝 | 44-VQFN (7x7 mm) exposed pad |
| 工作溫度 | Industrial, -40C to +85C |
| Supply Voltage Options | 2.5 V / 3.3 V / 5 V |
| On-Chip Debug | JTAG |
| RoHS 狀態 | Compliant |
| 安裝類型 | Surface Mount |
| Packaging | Tape & Reel (R suffix) |
ATMEGA644A-MUR 44-vqfn (7x7 mm) exposed pad 腳位配置指南
ATMEGA644A-MUR（44-vqfn (7x7 mm) exposed pad 封裝）的腳位配置。 此數位 IC 包含 GPIO、通訊介面（UART、SPI、I2C）與電源腳位。替代腳位功能與配置選項請參閱製造商資料表。對嵌入式系統設計與 PCB 佈局至關重要。
無詳細腳位定義資料： ATMEGA644A-MUR.
請參閱 資料表 以查看完整腳位配置。
典型應用
ATMEGA644A-MUR 適用於 6 應用s: Industrial Automation Controllers, Building and Home Automation Nodes, Motor Control and Power Electronics, Embedded Instrumentation and Data Loggers, Legacy AVR Design Maintenance, IoT Sensor Gateways.
Industrial Automation Controllers
The ATMEGA644A-MUR suits small PLC and I/O modules that need dual communication channels and solid memory headroom. Its two USARTs run Modbus RTU master and slave simultaneously at 115200 baud, while the 64 KB ISP flash hosts control logic plus a bootloader for field firmware updates via read-while-write. The three timers generate PWM for actuator control and time-stamp events, and 32 GPIO lines directly drive relays and optocoupler inputs. Operating over the -40C to +85C industrial range with a 5V-tolerant AVR core, it withstands factory-floor electrical noise better than 3.3V-only MCUs when paired with proper TVS and opto-isolation. The 44-VQFN exposed pad provides a low-inductance ground for noisy switching environments.
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Building and Home Automation Nodes
For wired automation nodes (DALI, RS-485, or KNX-style networks), the ATMEGA644A-MUR combines the TWI interface for local sensors with a USART for the network trunk, letting one MCU bridge room controllers to backbone wiring. The 2 KB EEPROM stores configuration, addressing, and calibration data through power cycles without external nonvolatile memory, and 64 KB flash accommodates protocol stacks plus OTA update bootloaders that exceed ATmega328 capacity. The real-time counter supports scheduling functions with a 32.768 kHz crystal on the low-frequency oscillator - note per AVR536 that crystal load capacitance must be re-verified on 644A. The 44-VQFN (7x7 mm) footprint fits compact wall-mounted modules.
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Motor Control and Power Electronics
The ATMEGA644A-MUR handles fan, pump, and small-bldc control using its PWM-capable timers: two 8-bit timers with compare outputs plus a 16-bit timer provide phase-correct and fast PWM modes for three-phase generation at 20 MHz resolution. Its fast single-cycle ALU executes PI control loops well within 10 kHz PWM ISR budgets, while 4 KB SRAM holds multiple control structures and fault logs. Dual USARTs report telemetry to a supervisory PLC. The industrial temperature rating and 5V operation give noise margin in drive environments; the exposed-pad VQFN should be soldered to a solid ground pour for thermal and EMI performance. Gate drivers remain external, keeping the MCU isolated from power stages.
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Embedded Instrumentation and Data Loggers
Bench instruments, environmental loggers, and portable test gear benefit from the ATMEGA644A-MUR's balance of ADC interfacing, memory, and interfaces. The device's 32 general purpose I/O lines multiplex sensor buses (SPI and TWI simultaneously) for multi-sensor front ends, while 64 KB flash stores lookup tables, calibration curves, and a USB/UART protocol stack. The 4 KB SRAM buffers time-series data between logging bursts, and the 2 KB EEPROM preserves configuration and thresholds across battery swaps. With a 20 MHz clock it timestamps events at sub-microsecond resolution, and the JTAG port enables in-system debugging during instrument development. Supply operation at 2.5V/3.3V/5V eases integration with analog front ends.
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Legacy AVR Design Maintenance
Thousands of shipped products were designed around the ATmega644; the ATMEGA644A-MUR is Microchip's sanctioned path for continuing those builds as original stock depletes. Per application note AVR536, the 644A is functionally equivalent with one documented difference - reduced low-frequency crystal oscillator drive strength - so existing boards using 32.768 kHz crystals should verify load capacitance and ESR compliance before switching BOMs. The identical pinout, memory map, and peripheral set mean firmware recompiles without source changes, and the R-suffix tape-and-reel format suits contract manufacturers' assembly lines. XAIPART stocks the 644A family alongside 644P/644PA variants for second-sourcing flexibility.
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IoT Sensor Gateways
In low-power IoT gateways, the ATMEGA644A-MUR aggregates wireless module data (sub-GHz RF or Bluetooth UART modules) on USART1 while serving a local display and keys over TWI/SPI, with the second USART free for diagnostics. The 64 KB flash hosts both the radio protocol framing and a field-updatable bootloader leveraging read-while-write flash, and 4 KB SRAM provides ring buffers that prevent packet loss during radio duty cycles. When mains power is absent, designers drop in the pin-compatible ATMEGA644PA whose picoPower sleep modes cut current below the 644A baseline. The 5V-capable core directly drives LED indicators and level-shifts legacy 5V peripherals without translators, simplifying mixed-voltage gateway designs.
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推薦產品摘要
工程參考資料，適用於 ATMEGA644A-MUR — 比較、設計指引及合規資訊。
選型指南
與替代品比較
| 參數 | 本產品 | ATMEGA644A-MU | ATMEGA644PA-MUR | ATMEGA1284P-MUR | ATMEGA164PA-MU |
|---|---|---|---|---|---|
| Package | 44-VQFN (7x7 mm) exposed pad | 44-VQFN (7x7 mm) - same | 44-VQFN (7x7 mm) - same | 44-VQFN (7x7 mm) - same | 44-VQFN (7x7 mm) - same |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Flash Memory | 64 KB | 64 KB | 64 KB | 128 KB | 16 KB |
| SRAM | 4 KB | 4 KB | 4 KB | 16 KB | 1 KB |
| EEPROM | 2 KB | 2 KB | 2 KB | 4 KB | 512 B |
| Max Clock Frequency | 20 MHz | 20 MHz | 20 MHz | 20 MHz | 20 MHz |
| PicoPower Features | No | No | Yes | Yes | Yes |
主要差異化特點
- Full 64 KB flash in pin-compatible footprint (對比ATMEGA164PA-MU)
- Cost-optimized vs picoPower variants (對比ATMEGA644PA-MUR)
- Memory headroom trade-off (對比ATMEGA1284P-MUR)
設計說明
When migrating from the original ATmega644 to the ATmega644A, verify crystal specifications: per Microchip application note AVR536 (doc8279), the ATmega644A reduces the low-frequency crystal oscillator drive strength. Crystals with marginal ESR or oversized load capacitance may fail to start, especially at cold temperature. Recalculate CL with the new oscillator parameters and test startup across the full temperature range and across several crystal lots before releasing the BOM change. This is the single most common 644-to-644A field issue.
Solder the exposed pad of the 44-VQFN package to a solid ground plane with an array of vias; it is the primary ground return and improves thermal and EMI performance. Place 100 nF ceramic decoupling capacitors at VCC and AVCC pins within 2 mm of each pin, and add 10 uF bulk capacitance near the supply entry. Keep the JTAG header routed short to preserve signal integrity for in-system debug, and reserve the JTAG pins (PC2-PC5) routing flexibility in case JTAGEN fuse is disabled to reclaim four GPIO lines.
Power the AVR core from a clean 5V or 3.3V rail matching your target clock: per the family speed-grade table concept, 20 MHz operation requires the higher voltage range, while lower voltage operation reduces the maximum safe clock. Connect AVCC to VCC through an LC filter (ferrite bead plus 100 nF/1 uF) when using the ADC, and tie AREF to ground via 100 nF when using the internal reference. Estimated current budget: active 20 MHz operation plus peripherals typically lands well below 25 mA, so a 100 mA LDO provides ample margin.
合規資訊
EU RoHS and REACH compliant per distributor listings (Abacus Technologies) for the ATmega644A family; DRC conflict-free status reported. Halogen-free status not stated in verified data.