Overview
The Atmel ATmega165A/165PA/325A/325PA/3250A/3250PA/645A/645P/6450A/6450P is a low-power CMOS 8-bit microcontroller based on the AVR enhanced RISC architecture. By executing powerful instructions in a single clock cycle, this microcontroller achieves throughputs approaching 1 MIPS per MHz allowing the system designer to optimize power consumption versus processing speed.
   
Features
• High performance, low power Atmel® AVR® 8-Bit Microcontroller
• Advanced RISC architecture
    – 130 powerful instructions – most single clock cycle execution
    – 32 × 8 general purpose working registers
    – Fully static operation
    – Up to 16MIPS throughput at 16MHz (Atmel ATmega165PA/645P)
    – Up to 20MIPS throughput at 20MHz (Atmel ATmega165A/325A/
        325PA/645A/3250A/3250PA/6450A/6450P)
    – On-chip 2-cycle multiplier
• High endurance non-volatile memory segments
    – In-system self-programmable flash program memory
        • 16KBytes (ATmega165A/ATmega165PA)
        • 32KBytes (ATmega325A/ATmega325PA/ATmega3250A/ATmega3250PA)
        • 64KBytes (ATmega645A/ATmega645P/ATmega6450A/ATmega6450P)
    – EEPROM
        • 512Bytes (ATmega165A/ATmega165PA)
        • 1Kbytes (ATmega325A/ATmega325PA/ATmega3250A/ATmega3250PA)
        • 2Kbytes (ATmega645A/ATmega645P/ATmega6450A/ATmega6450P)
    – Internal SRAM
• 1KBytes (ATmega165A/ATmega165PA)
• 2KBytes (ATmega325A/ATmega325PA/ATmega3250A/ATmega3250PA)
• 4KBytes (ATmega645A/ATmega645P/ATmega6450A/ATmega6450P)
    – Write/erase cycles: 10,000 flash/100,000 EEPROM
    – Data retention: 20 years at 85°C/100 years at 25°C (1)
    – Optional Boot Code Section with Independent Lock Bits
        • In-System Programming by On-chip Boot Program
        • True read-while-write operation
    – Programming lock for software security
• Atmel QTouch® library support
    – Capacitive touch buttons, sliders and wheels
    – Atmel QTouch and QMatrix acquisition
    – Up to 64 sense channels
• JTAG (IEEE std. 1149.1 compliant) interface
    – Boundary-scan capabilities according to the JTAG standard
    – Extensive on-chip debug support
    – Programming of Flash, EEPROM, Fuses, and Lock Bits through the JTAG Interface
• Peripheral Features
    – Two 8-bit Timer/Counters with Separate Prescaler and Compare Mode
    – One 16-bit Timer/Counter with Separate Prescaler, Compare Mode, and Capture Mode
    – Real time counter with separate oscillator
    – Four PWM channels
    – 8-channel, 10-bit ADC
    – Programmable serial USART
    – Master/Slave SPI Serial Interface
    – Universal Serial Interface with Start Condition detector
    – Programmable Watchdog Timer with separate on-chip oscillator
    – On-chip Analog Comparator
    – Interrupt and Wake-up on pin change
• Special microcontroller features
    – Power-on reset and programmable Brown-out detection
    – Internal calibrated oscillator
    – External and internal interrupt sources
    – Five sleep modes: Idle, ADC Noise Reduction, Power-save, Power-down and Standby
• I/O and packages
    – 54/69 programmable I/O lines
    – 64/100-lead TQFP, 64-pad QFN/MLF and 64-pad DRQFN
• Speed grade:
    – ATmega 165A/165PA/645A/645P: 0 - 16MHz @ 1.8 - 5.5V
    – ATmega325A/325PA/3250A/3250PA/6450A/6450P: 0 - 20MHz @ 1.8 - 5.5V
• Temperature range:
    – -40°C to 85C industrial
• Ultra-low power consumption (picoPower® devices)
    – Active mode:
        • 1MHz, 1.8V: 215µA
        • 32kHz, 1.8V: 8µA (including oscillator)
    – Power-down mode: 0.1µA at 1.8V
    – Power-save mode: 0.6µA at 1.8V (Including 32kHz RTC)