The ATmega644 is often used as a "bigger & badder" Arduino. There are bootloaders available for it, and Arduino extensions that support it.

There are three versions - the ATmega644, which has typical speed and voltage modes, the ATmega644V, which is a reduced voltage/speed version, and the ATmega644A/PA which has an additional USART and 7 more interrupts. The ATmega644V will run from supplies as low as 1.8V, but it's maximum frequency is reduced from 20MHz to 10MHz.

Power Supply vs. Maximum Frequency

The calculator below provides a way to find the maximum operating frequency for any valid power supply voltage (2.7 to 5.5). Enter the power supply voltage and click "Calculate Max Frequency" to find the ATmega644's specified maximum clock speed at your Vcc.

Maximum Frequency at Vcc Calculator for ATmega644/V/A/PA

Vcc (volts):


Interesting Parameters
ATmega644 Features
Flash 64k64k
RAM 4k4k
I/O Pins 3232
Interrupts 2835
USI 00
SPI 11
ADC Channels 88
RT Counter (w/osc) 11
Timers (8-bit) 22
Timers (16-bit) 11
PWM (8-bit) 44
PWM (16-bit) 22
Characteristic Value
Power Consumption (approximate) 1.125mA/MHz
Maximum I/O Current (per pin) 40mA
Maximum I/O Current (all ports) 100mA(low)/150mA(high)
Maximum I/O Current (total) 200mA (PDIP)
Maximum I/O Current (total)400mA (PDIP/QFP/MLF)
Atmel ATmega644 Datasheet

Link to Atmel ATmega644/V datasheet Link to Atmel ATmega644A/PA datasheet

Atmel ATmega644 Pinout
ATmega644PA-PU pinout ATmega644PA-AU pinout
"Minimal" ATmega644 Schematic Diagram

A minimal ATmega644 circuit consists of an ATmega644. Everything else is optional. The circuit below shows a programming port, reset circuit, and a crystal oscillator. Any or all of these could be left off and the device would function perfectly well. By default the unit runs from the 1MHz internal RC oscillator.

ATmega644 minimal schematic diagram
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