The Arduino ADK is a microcontroller board based on the ATmega2560 (datasheet). It has a USB host interface to connect with Android based phones, based on the MAX3421e IC. It has 54 digital input/output pins (of which 14 can be used as PWM outputs), 16 analog inputs, 4 UARTs (hardware serial ports), a 16 MHz crystal oscillator, a USB connection, a power jack, an ICSP header, and a reset button.

Technical Specification:
Microcontroller : ATmega2560
Operating Voltage : 5V
Input Voltage (recommended) : 9V
Input Voltage (limits) : 6-18V
Digital I/O Pins : 54 (of which 14 provide PWM output)
Analog Input Pins : 16
DC Current per I/O Pin : 40 mA
DC Current for 3.3V Pin : 50 mA
Flash Memory : 256 KB of which 8 KB used by bootloader
SRAM : 8 KB
EEPROM : 4 KB
Clock Speed : 16 MHz
For more information, please visit this products data sheet.