The main feature of the ATmega8U2/16U2/32U2 MCU's is the USB 2.0 engine. It is the basis for the USB to TTL
converter for the R3 series Uno and Mega 2560 boards. There is no ADC section, and little I/O in general. A
perfect use would be a USB to parallel, USB to Serial TTL, USB to SPI, etc.
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 ATmega32U2's
specified maximum clock speed at your Vcc.
Maximum Frequency Calculator for ATmega8U2/16U2/32U2
|I/O Pins ||22|
|ADC Channels ||0|
|RT Counter (w/osc)||0|
|Timers (8-bit) ||1|
|Timers (16-bit) ||1|
|PWM (8-bit) ||2|
|PWM (16-bit) ||3|
|USB 2.0 Engine ||1|
|Price (1's) ||$3.78||$3.80||$4.50|
|Power Consumption (approximate) ||5.5mA + (0.5/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)|
Link to ATmega8U2/16U2/32U2 datasheet from Atmel's website.
ATmega8U2/16U2/32U2 "Minimal" Circuit Diagram
A minimal ATmega8U2/16U2/32U2 circuit consists of an ATmega8U2/16U2/32U2 and a few external parts. Because there are two ways this can be
connected, bus-powered or self-powered, there are two drawings.
In the self-powered configuration the program needs to know if the USB is powered or not. Use PC2 for that, or
any pin you feel like using. The reset circuit could be anything, but there is an internal register that will allow
the USB to reset the MCU, so there are choices to make.