ATMEGA644-20PU - 8-bit AVR MCU 64KB 20MHz DIP-40 | Microchip
MPN: ATMEGA644-20PU ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $11.13 | $11.13 |
| 10 | $10.2 | $102.00 |
| 100 | $9.45 | $945.00 |
| 500 | $8.6 | $4,300.00 |
| 1,000 | $7.4 | $7,400.00 |
ATMEGA644-20PU Overview
An 8-bit microcontroller is a self-contained computing IC that integrates a processor core, program memory, data memory, and peripherals such as timers, UARTs, and analog-to-digital converters on a single die. Within the product hierarchy, the ATmega644 belongs to the AVR ATmega family of flash-based MCUs, which sit under the broader categories of 8-bit microcontrollers, embedded processors, and integrated circuits. The AVR architecture executes most instructions in a single clock cycle through its 32 general-purpose working registers, delivering high code efficiency for embedded control systems.
Key features of the ATMEGA644-20PU include 64KB of self-programmable Flash memory with read-while-write capability, 32 general-purpose I/O lines, two USARTs for serial communication, and three flexible timer/counters with compare modes and PWM outputs. The device also integrates a byte-oriented two-wire serial interface (TWI/I2C), an SPI serial interface, a 10-bit ADC, a programmable watchdog timer with separate on-chip oscillator, and an on-chip analog comparator.
Technically, the AVR core uses a Harvard architecture with separate program and data buses. JTAG (IEEE 1149.1 compliant) boundary-scan and on-chip debugging are supported, and In-Circuit Serial Programming (ICSP) allows firmware updates without removing the chip from the board. Boot loader support with self-programming enables field firmware upgrades, while five sleep modes (including power-down and power-save) reduce current consumption in battery-conscious designs.
Typical applications include industrial control and automation panels, embedded instrumentation and data loggers, and educational or hobbyist single-board systems. The 40-pin PDIP package is a major advantage for prototyping, repair, and low-volume production, since the chip can be socketed and replaced without soldering equipment.
When designing with this device, remember that the full 20 MHz speed grade requires a supply voltage in the higher portion of the operating range; for low-voltage operation at 2.7V to 5.5V the clock frequency must be derated according to the speed-grade curves in the manufacturer datasheet. Decouple VCC and AVCC separately with 100 nF ceramic capacitors placed close to the pins.
This page synthesizes distributor pricing, drop-in alternatives from the same ATmega family, design notes, and application guidance not found together on the manufacturer datasheet, with pricing referenced as of 2026-09-18.
Drop-in alternatives for ATMEGA644-20PU — 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 ATMEGA644-20PU (same form factor and footprint) — differing in EEPROM, Package, SRAM, Core Architecture, Mounting Type.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
ATMEGA644P-20PU
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$8.55 / Unit
View Datasheet →ATMEGA644PA-PU
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$5.15 / Unit
View Datasheet →ATMEGA1284-20PU
✅ Drop-In ⚠️ 参数待验证📋 Reference alternative (not in catalog)
ATMEGA64A-PU
✅ Drop-In ⚠️ 参数待验证📋 Reference alternative (not in catalog)
ATMEGA32A-PU
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$3.85 / Unit
View Datasheet →ATMEGA644-20PU Maximum Ratings & Electrical Characteristics
| Core Architecture | 8-bit AVR enhanced RISC |
| Program Memory Size | 64 KB (32K x 16) Flash |
| Program Memory Type | ISP FLASH (read-while-write) |
| SRAM | 4 KB |
| EEPROM | 2 KB |
| Maximum Clock Frequency | 20 MHz |
| Operating Voltage Range | 2.7 V to 5.5 V |
| General Purpose I/O | 32 I/O lines |
| USARTs | 2 |
| Timer/Counters | 3 (with compare modes and PWM) |
| Serial Interfaces | SPI, TWI (I2C compatible) |
| ADC Resolution | 10-bit |
| JTAG | Yes (IEEE 1149.1 boundary scan, on-chip debug) |
| Sleep Modes | 5 (including power-down, power-save) |
| Package | 40-PDIP (0.600 in, 15.24 mm) |
| Mounting Type | Through-Hole |
| Operating Temperature | -40 C to +85 C (industrial) |
| RoHS Status | Compliant (Green) |
ATMEGA644-20PU 40-pdip (0.600 in, 15.24 mm) Pin Configuration Guide
Pin configuration for ATMEGA644-20PU (40-pdip (0.600 in, 15.24 mm) 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 ATMEGA644-20PU.
Refer to the datasheet for full pin configuration.
Typical Applications
ATMEGA644-20PU is suitable for 6 applications: Industrial Control and Automation, Embedded Data Logging, Test and Measurement Instruments, UART Communication Nodes, Home Automation and IoT Controllers, Education and Prototyping.
Industrial Control and Automation
The ATMEGA644-20PU fits industrial control panels because its -40 C to +85 C industrial temperature rating, watchdog timer with independent on-chip oscillator, and 32 GPIO lines provide the reliability and I/O density that factory automation nodes require. Two USARTs allow simultaneous Modbus RTU field-bus communication and a local HMI serial link, while three timer/counters generate PWM outputs for actuator or fan control at 20 MHz resolution. The 10-bit ADC reads analog sensor feedback directly without an external converter. Because the PDIP-40 package is socketed in serviceable equipment, field technicians can replace the MCU in minutes, reducing downtime in legacy industrial installations.
Recommended
Embedded Data Logging
For data-logger designs, the ATMEGA644-20PU offers 64KB of self-programmable Flash for firmware plus 4KB of SRAM for buffering, enough to log thousands of sensor samples between writes to external storage. Its 10-bit ADC with up to eight single-ended channels captures multi-sensor analog inputs, and the TWI (I2C) interface connects RTC and EEPROM chips for time-stamping and overflow storage. The power-down and power-save sleep modes cut average current dramatically in battery-powered loggers, and the byte-oriented TWI plus two USARTs support both local data offload and wireless modem attachment. The through-hole DIP-40 package simplifies prototype iterations during logger development.
Recommended
Test and Measurement Instruments
Bench instruments and DIY measurement gear benefit from the ATMEGA644-20PU's combination of 20 MHz throughput, JTAG on-chip debugging, and generous 64KB Flash for menu-driven UI firmware. Three timer/counters with input-capture capability (ICP1) enable frequency and pulse-width measurement with microsecond resolution, while the 10-bit ADC digitizes probe inputs. Two USARTs allow one channel for a PC/USB bridge and another for an auxiliary instrument module. The JTAG (IEEE 1149.1) boundary-scan support permits production test of assembled boards. The socketable PDIP-40 package is a practical advantage for repairable lab equipment where firmware updates and chip swaps are routine.
Recommended
UART Communication Nodes
The two independent USARTs of the ATMEGA644-20PU make it a strong choice for protocol-translation and serial-network nodes. One UART can service an RS-485 field bus while the second handles a local debug console or GSM/NB-IoT modem, all managed by the 64KB Flash firmware with read-while-write boot-loader support for remote field upgrades. Hardware-supported SPI and TWI interfaces add connectivity to Ethernet controllers, displays, and memory devices. At 20 MHz, the AVR core sustains multi-channel serial traffic at 115200 baud with ample headroom for CRC and framing computation. Industrial temperature rating and the watchdog timer add link-recovery robustness for unattended communication nodes.
Recommended
Home Automation and IoT Controllers
In home automation hubs and sensor controllers, the ATMEGA644-20PU balances memory, peripherals, and cost. The TWI interface reads temperature, humidity, and light sensors across an I2C bus, while GPIO directly drives relays and optocoupled outputs for lighting and appliance control. The power-save mode with asynchronous Timer 2 keeps a real-time clock running in microamp-level sleep, waking the MCU on schedule to sample sensors and transmit via an attached wireless module over USART. With 4KB SRAM, lightweight TCP or RF mesh stacks fit comfortably in firmware. The DIP-40 package lets hobbyists and small manufacturers rework and reprogram boards easily during development.
Recommended
Education and Prototyping
The ATMEGA644-20PU is a favorite in university embedded-systems courses and hobbyist single-board computers because the 40-pin PDIP through-hole package can be inserted into a ZIF socket or breadboard adapter and programmed repeatedly without surface-mount tools. Its 64KB Flash accommodates substantial student projects, and the ATmega architecture - 32 working registers, single-cycle execution - teaches RISC concepts cleanly. Community support is extensive: the MightyCore Arduino hardware package provides full core support for the ATmega644, letting students program with the familiar Arduino IDE while learning registers and datasheets. ICSP programming via USBasp requires only six wires, making lab setups inexpensive and robust.
Recommended
Recommended Products Summary
Engineering reference data for ATMEGA644-20PU — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ATMEGA644P-20PU | ATMEGA644PA-PU | ATMEGA1284-20PU | ATMEGA32A-PU |
|---|---|---|---|---|---|
| Package | 40-PDIP (0.600 in, 15.24 mm) | 40-PDIP - same | 40-PDIP - same | 40-PDIP - same | 40-PDIP - same |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Flash Memory | 64 KB | 64 KB | 64 KB | 128 KB | 32 KB |
| SRAM | 4 KB | 4 KB | 4 KB | 16 KB | 2 KB |
| EEPROM | 2 KB | 2 KB | 4 KB | 4 KB | 1 KB |
| Max Clock Frequency | 20 MHz | 20 MHz | 20 MHz | 20 MHz | 16 MHz |
| USARTs | 2 | 2 | 2 | 2 | 1 |
| Power Technology | Standard AVR core | picoPower | picoPower | Standard AVR core | Standard AVR core |
Key Differentiators
- Socketable through-hole 40-PDIP package (vs ATMEGA644-20AU (TQFP44 SMD variant))
- 64KB Flash / 4KB SRAM at 20 MHz (vs ATMEGA32A-PU)
- Memory headroom at identical cost tier to smaller family parts (vs ATMEGA1284-20PU)
Design Notes
Estimated: The ATmega644-20PU draws up to approximately 20-25 mA active at 20 MHz, 5V (per family datasheet active-current figures); budget supply rails accordingly and decouple VCC and AVCC each with 100 nF ceramic capacitors placed within a few millimeters of the pins, plus a bulk 10 uF capacitor per board. AVCC must be connected to VCC even if the ADC is unused. If ADC accuracy matters, filter AVCC through an LC network (e.g., 10 uH + 100 nF) rather than tying it directly to the digital rail.
The -20 speed grade reaches 20 MHz only at the upper end of the supply range (5V nominal); running the full 20 MHz below the rated minimum voltage for the speed grade violates the voltage-frequency curve and can cause intermittent failures. Also note that PB6/PB7 function as XTAL1/XTAL2 when an external crystal is used, removing two port-B I/O lines from general use. Verify fuse settings (clock source, JTAGEN, brown-out) before first power-up - incorrect clock fuses are the most common cause of a seemingly dead board.
For through-hole DIP-40 designs, keep the crystal within 1 cm of PB6/PB7 with appropriate load capacitors (typically 22 pF for common crystals - verify against crystal specification), and route the RESET line short with a 10 kOhm pull-up to VCC for reliable ICSP programming. If JTAG is enabled and pins PC2-PC5 are needed as GPIO, clear the JTAGEN fuse or disable JTAG in software by writing the JTD bit twice within four cycles, per the manufacturer datasheet.
In mixed-signal layouts, keep the ADC input traces away from USART and crystal lines and use a solid ground plane. For socketed production boards, use a machined-pin socket rather than a stamped socket for contact reliability over temperature cycling in the -40 C to +85 C industrial range. When replacing an ATmega644 with an ATmega644P/PA on an existing board, no layout change is needed, but re-verify brown-out and sleep-current measurements since picoPower dies exhibit different current profiles.
Compliance Information
FindIC product data lists the ATMEGA644-20PU as GREEN (lead-free, RoHS-oriented) industrial-temperature part. REACH and conflict-minerals status not stated in provided data.
