The ATmega8 is an early 28-pin device with 8kB of flash. It was the foundation for the Arduino, and is still
very popular. The ATmega8A is an improved version, and is the only one available today. By current standards
it is a little short of features, but it performs as well as it's more feature-rich relatives.
Power Supply vs. Maximum Frequency
The ATmega8 has a different clock than many other AVR's, featuring an internal clock that runs at 1MHz, 2MHz,
4MHz, and 8MHz, rather than having a divide by 8 fuse. The maximum frequency is 16MHz with an external crystal.
Maximum Frequency Calculator for ATmega8
|I/O Pins ||23|
|ADC Channels ||6|
|RT Counter (w/osc)||0|
|Timers (8-bit) ||2|
|Timers (16-bit) ||1|
|PWM (8-bit) ||2|
|PWM (16-bit) ||1|
|Price (1's) ||$3.40|
|Power Consumption (approximate) ||1.1mA/MHz|
|Maximum I/O Current (per pin) ||40mA|
|Maximum I/O Current (all ports) ||100mA|
|Maximum I/O Current (total) ||200mA (PDIP)|
|Maximum I/O Current (total) ||400mA (PDIP/QFP/MLF)|
Link to ATmega8 datasheet from Atmel's website.
ATmega8 "Minimal" Circuit Diagram
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 8MHz internal RC oscillator divided by 8, for a
1MHz system clock.