ATMEGA645A-MU - 8-Bit AVR MCU 16MHz 64KB Flash | Microchip
MPN: ATMEGA645A-MU ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $5.77 | $5.77 |
| 10 | $5.19 | $51.90 |
| 100 | $4.62 | $462.00 |
| 500 | $4.16 | $2,080.00 |
| 1,000 | $3.7 | $3,700.00 |
ATMEGA645A-MU Overview
An 8-bit AVR ATmega microcontroller is a Harvard-architecture RISC processor that executes most instructions in a single clock cycle, positioning it in the embedded hierarchy as: ATMEGA645A -> ATmega family -> AVR 8-bit MCU -> microcontroller unit (MCU). These devices integrate program memory, data memory, peripherals, and a CPU core on a single die, making them a complete embedded control solution.
Key features include single-cycle RISC execution through 32 general-purpose working registers, read-while-write Flash for self-programming, JTAG boundary-scan and on-chip debugging, and a rich analog and timer peripheral set. The device operates from 1.8V to 5.5V, supporting both battery-powered and 5V industrial designs.
The AVR core combines a fast ALU with the 32-register file, which is directly connected to the ALU, allowing two independent registers to be accessed in one instruction executed in one clock cycle. This architecture achieves throughputs up to 16 MIPS at 16 MHz, roughly ten times faster than conventional CISC microcontrollers. Peripherals include an 8-channel 10-bit ADC, USART, SPI, two-wire interface (TWI/I2C), timers with PWM, and an on-chip temperature sensor.
Typical applications include industrial control panels, HVAC and building automation, consumer appliances, metering systems, and LCD-equipped instruments, where the ATMEGA645A's large 64 KB Flash accommodates C-based firmware with graphics or communication stacks.
When designing, plan the clock source early: at 5V the device supports up to 16 MHz, and an external crystal plus decoupling on AVCC is required for full ADC accuracy.
This page synthesizes verified distributor pricing, same-family drop-in alternatives, and practical AVR design guidance not found in the manufacturer datasheet.
Drop-in alternatives for ATMEGA645A-MU — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with ATMEGA645A-MU (same form factor and footprint) — differing in Package, Flash Memory, Core Processor, ADC Resolution, EEPROM.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
ATMEGA645-16MUR
✅ Drop-In✓ In Stock
$3.35 / Unit
View Datasheet →ATMEGA6450A-MU
✅ Drop-In ⚠️ 参数待验证📋 Reference alternative (not in catalog)
ATMEGA645P-MU
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$4.21 / Unit
View Datasheet →ATMEGA325A-MU
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$3.49 / Unit
View Datasheet →ATMEGA645A-MU Maximum Ratings & Electrical Characteristics
| Core Processor | AVR |
| Core Size | 8-Bit |
| Speed | 16 MHz |
| Flash Memory | 64 KB (32K x 16) |
| EEPROM Size | 2 KB |
| RAM Size | 4 KB |
| Supply Voltage (Vcc/Vdd) | 1.8 V to 5.5 V |
| Number of I/O | 54 / 69 general purpose I/O lines |
| Package | 64-QFN (9x9 mm) Exposed Pad (64-VFQFN) |
| Mounting Type | Surface Mount |
| ADC Resolution | 10-bit |
| Oscillator Type | Internal + External |
| Programming Interface | ISP, JTAG, ICSP |
| Series | AVR ATmega |
| RoHS Status | Compliant |
ATMEGA645A-MU 64-qfn (9x9 mm) exposed pad (64-vfqfn) Pin Configuration Guide
Pin configuration for ATMEGA645A-MU (64-qfn (9x9 mm) exposed pad (64-vfqfn) package). This digital IC includes GPIO, communication interfaces (UART, SPI, I2C), and power pins. Refer to the manufacturer datasheet for alternate pin functions and configuration options. Essential for embedded system design and PCB layout.
No detailed pinout data available for ATMEGA645A-MU.
Refer to the datasheet for full pin configuration.
Typical Applications
ATMEGA645A-MU is suitable for 6 applications: Industrial Control Panels, HVAC and Building Automation, Metering and Instrumentation, Consumer Appliances, Battery-Powered Portable Devices, Embedded Development and Prototyping.
Industrial Control Panels
The ATMEGA645A-MU fits industrial control panels because its 5V-tolerant 1.8V to 5.5V supply range aligns with legacy factory logic levels, its 54 general-purpose I/O lines drive relays, contactors, and indicator banks directly, and its 8-channel 10-bit ADC samples analog sensor inputs such as potentiometers and current-sense outputs. The 64 KB Flash is large enough to hold state machines, MODBUS-style serial routines on the USART, and configuration data in the 2 KB EEPROM. In a typical panel, the MCU runs at 16 MHz from a crystal, polls discrete inputs each scan, and uses timer PWM outputs for actuator control; unlike 32-bit alternatives it requires no external memory and draws low static power, simplifying enclosed thermal design.
Recommended
HVAC and Building Automation
Building automation nodes benefit from the ATMEGA645A-MU's combination of a two-wire interface (TWI/I2C) for temperature and humidity sensors, a USART for RS-485 trunk communication via external transceivers, and timer PWM outputs for damper and fan control. The 1.8V to 5.5V rail flexibility lets designers run the logic from a single 3.3V or 5V wall-adapter supply, while the 64 KB Flash accommodates scheduling tables, PID loops, and firmware-update bootloaders without external storage. The 4 KB SRAM holds network buffers comfortably, and the 2 KB EEPROM retains setpoints through power loss. Because the QFN's exposed pad improves board-level heat spreading, thermostat enclosures with no airflow remain within safe junction limits at typical mA-level loads.
Recommended
Metering and Instrumentation
Energy and utility metering designs use the ATMEGA645A-MU's 8-channel 10-bit ADC for multi-channel voltage and current sampling, its 16 MHz RISC core for real-time RMS computation, and its EEPROM for tamper and consumption logs that must survive power interruption. The 64 KB Flash stores calibration tables plus LCD-driving firmware, and JTAG boundary scan supports production test of dense meter PCBs. With the device running at 5V, ADC noise margin improves over 3V designs, an advantage when measuring small shunt signals. The read-while-write Flash enables field firmware updates over the meter's communication port without halting measurement routines, an important regulatory convenience for deployed meter fleets.
Recommended
Consumer Appliances
White goods and small appliances employ the ATMEGA645A-MU to run user interfaces (keys, encoders, and segment LCDs), motor PWM control, and safety interlocks in one chip. The wide 1.8V to 5.5V supply range tolerates unregulated auxiliaries derived from mains supplies, and the internal oscillator option allows cost-down designs that skip the crystal on non-timing-critical products. Its 64 KB Flash provides headroom for localized UI strings, diagnostic code, and OTA-style serial bootloaders, while the 2 KB EEPROM stores cycle counters and error logs. The 64-QFN's small 9x9 mm footprint fits crowded appliance control PCBs, and the exposed pad anchors the part against vibration and thermal cycling typical of kitchen environments.
Recommended
Battery-Powered Portable Devices
Portable instruments leverage the ATMEGA645A-MU's low-power AVR core and multiple sleep modes to stretch battery life while retaining 64 KB of code space for feature-rich firmware. Operating down to 1.8V means the device runs directly from two alkaline cells or a single lithium coin cell through most of the discharge curve, avoiding a boost converter. Designers typically clock at 1-8 MHz via the internal RC oscillator in active mode, drop to power-save sleep between measurements, and use timer or TWI wakeups from the real-time peripherals. The 4 KB SRAM buffers data-logger samples, and the 10-bit ADC digitizes sensor channels without an external converter, minimizing bill-of-materials cost in handheld enclosures.
Recommended
Embedded Development and Prototyping
The ATMEGA645A-MU is a strong prototyping vehicle because Microchip supports it with the MPLAB SNAP and AVR ISP programmers through ICSP and JTAG, per the official product page, enabling on-chip debugging on the target board rather than guess-and-reflash cycles. The ATmega645A family is documented in the consolidated ATmega165A/325A/645A datasheet together with migration note AVR500, so engineers moving between 32 KB and 64 KB family members share one reference. The large 64 KB Flash removes early size constraints for C code, and the DIP-free QFN suits final-form-factor prototype PCBs. Open-source avr-gcc toolchains and Arduino-style bootloaders run on the AVR core, letting teams iterate firmware quickly before production freeze.
Recommended
Recommended Products Summary
Engineering reference data for ATMEGA645A-MU — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ATMEGA645-16MUR | ATMEGA6450A-MU | ATMEGA645P-MU | ATMEGA325A-MU |
|---|---|---|---|---|---|
| Package | 64-QFN (9x9) | 64-QFN (9x9) - same | 64-QFN (9x9) - same | 64-QFN (9x9) - same | 64-QFN (9x9) - same |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Flash Memory | 64 KB | 64 KB | 64 KB | 64 KB | 32 KB |
| SRAM | 4 KB | 4 KB | 4 KB | 4 KB | 2 KB |
| Max Clock | 16 MHz | 16 MHz | 16 MHz | 16 MHz | 16 MHz |
| Supply Voltage | 1.8 V to 5.5 V | 1.8 V to 5.5 V | 1.8 V to 5.5 V | 1.8 V to 5.5 V | 1.8 V to 5.5 V |
| Low-Power Feature | Standard ATmega sleep modes | Standard | Standard | picoPower (lower sleep current) | Standard |
| Programming / Debug | ISP, JTAG, ICSP | ISP, JTAG | ISP, JTAG | ISP, JTAG | ISP, JTAG |
Key Differentiators
- Double the program memory for feature-rich firmware (vs ATMEGA325A-MU)
- picoPower variant available for battery designs (vs ATMEGA645P-MU)
- Compact thermally enhanced QFN over TQFP (vs ATMEGA645A-AU)
Design Notes
Decouple VCC and AVCC independently: place a 100 nF ceramic capacitor within 2 mm of each VCC pin and a separate 100 nF plus 10 uF pair on AVCC, connected to analog ground through an LC or RC filter. AVCC must not differ from VCC by more than 0.3V, per AVR family supply requirements. For ADC accuracy, keep the digital return path away from the analog ground region under the exposed pad; the 64-QFN exposed pad should be soldered to a grounded copper pour for both electrical grounding and heat spreading.
Clock frequency depends on supply voltage: 16 MHz operation is only valid at the upper end of the 1.8V-5.5V range, so check the frequency-versus-voltage curve in the ATmega645A datasheet before selecting a crystal. Also confirm that any replacement from the family (e.g., ATmega325A) matches fuse settings and JTAG enable state - JTAG is enabled by default on this family and the four JTAG pins are not available as GPIO unless the JTAGEN fuse is disabled, a frequent source of 'missing I/O pins' issues on port designs migrated from non-JTAG ATmegas.
For the 64-QFN (9x9) land pattern, design thermal vias under the exposed pad (roughly a 4x4 or 5x5 via array filled or tented per assembly capability) tied to the ground plane to improve both thermal performance and signal grounding. Trace lengths to the crystal should be kept under 10 mm with guard ground rings. Route the RESET line with a 10 kOhm pull-up and keep it short to support reliable ISP programming; on dense boards, bring RESET and the SPI ISP pins to a 6-pin programming header for in-circuit updates with MPLAB SNAP or equivalent AVR programmers.
Compliance Information
RoHS compliant per distributor listings (DigiKey/Mouser). REACH and halogen-free status not stated in the provided verified data.
