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ATmega328P-PU

8-bit AVR MCU, 32KB Flash, 20MHz, 28-PDIP, Arduino Uno core

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Manufacturer Part：

ATmega328P-PU

Package：

28-PDIP (0.300", 7.62mm)

Description

Product Overview

The ATmega328P-PU from Microchip Technology (formerly Atmel) is a high-performance, low-power 8-bit AVR RISC microcontroller with 32KB ISP Flash, 2KB SRAM, 1KB EEPROM, 23 I/O lines, 10-bit ADC, and 6 PWM channels in a 28-pin PDIP through-hole package. It is the MCU at the heart of the Arduino Uno and Nano boards.

Key Specifications

Core: 8-bit AVR RISC, 131 instructions, most single-cycle
Max Speed: 20MHz (at 4.5-5.5V)
Flash: 32KB (in-system programmable, read-while-write)
SRAM: 2KB
EEPROM: 1KB (100,000 write/erase cycles)
Supply Voltage: 1.8V ~ 5.5V
I/O Pins: 23
ADC: 6-channel 10-bit (PDIP) / 8-channel (TQFP/QFN)
PWM: 6 channels
Timers: 2× 8-bit + 1× 16-bit with capture/compare
Communication: USART, SPI (master/slave), I2C (TWI)
Watchdog Timer: With independent on-chip oscillator
Analog Comparator: 1
Operating Temperature: -40°C ~ 85°C
Package: 28-PDIP (0.300″, 7.62mm)
Power (1MHz, 1.8V): Active 0.2mA, Power-down 0.1µA, Power-save 0.75µA
Self-Programming: Boot loader support via USART or SPI

Features

picoPower technology for ultra-low power consumption
6 software-selectable sleep modes
32×8 general-purpose working registers
On-chip 2-cycle multiplier
20-year data retention at 85°C
QTouch library support for capacitive sensing
Internal calibrated RC oscillator (8MHz)
Programmable brown-out detection (BOD)
Through-hole PDIP package ideal for prototyping

Applications

Arduino Uno / Nano boards
Sensor interface and data acquisition
Battery-powered instruments
Home automation controllers
LED lighting and display control

Product Introduction:ATmega328P-PU Product Introduction

The ATmega328P-PU from Microchip Technology is the iconic 8-bit AVR microcontroller that powers the Arduino Uno, the world’s most popular development board. Its 32KB Flash provides ample program space for Arduino sketches, while the 2KB SRAM and 1KB EEPROM handle runtime variables and persistent settings. The 28-pin PDIP package makes it ideal for breadboard prototyping and through-hole assembly. The AVR RISC architecture executes most instructions in a single clock cycle, achieving near 1 MIPS per MHz throughput. The ATmega328P-PU supports in-system programming via SPI and self-programming through a boot loader, enabling firmware updates without a dedicated programmer. The -PU suffix indicates PDIP-28 package with industrial temperature range and tube packaging.

Working Principle:ATmega328P-PU Working Principle

The ATmega328P-PU uses the AVR enhanced RISC architecture with a 2-stage pipeline: while one instruction is being executed, the next is being fetched from Flash. The 32×8 general-purpose working registers are directly connected to the ALU, allowing two registers to be accessed in a single clock cycle — a key factor in the 1 MIPS/MHz throughput. The Harvard architecture separates 32KB Flash (program) from 2KB SRAM (data) address spaces, with the 1KB EEPROM accessed through dedicated I/O registers. The I/O memory-mapped peripheral registers control timers, USART, SPI, TWI, ADC, and pin functions. The 10-bit ADC uses a successive approximation register (SAR) with a conversion time of 13-260µs depending on clock prescaler. The 6 PWM channels are generated by the timer/counter modules in Fast PWM or Phase-Correct PWM modes. Sleep modes (Idle, ADC Noise Reduction, Power-save, Power-down, Standby, Extended Standby) shut down unused clock domains and peripherals to reduce power consumption down to 0.1µA in Power-down mode.

Pin Description:ATmega328P-PU Pin Definition and Functions

Pin	Name	Key Alternate Functions
1	PC6 (RESET)	Reset input (active low); can be disabled by fuse
2	PD0 (RXD)	USART receive, PCINT18
3	PD1 (TXD)	USART transmit, PCINT19
4	PD2 (INT0)	External interrupt 0, PCINT18
5	PD3 (INT1/OC2B)	External interrupt 1, PWM Timer2
6	PD4	T0, XCK, PCINT20
7	VCC	Power supply (1.8-5.5V)
8	GND	Ground
9	PB6 (XTAL1)	Crystal oscillator input / TOSC1
10	PB7 (XTAL2)	Crystal oscillator output / TOSC2
11	PD5 (OC0B/T1)	PWM Timer0, Timer1 clock
12	PD6 (OC0A/AIN0)	PWM Timer0, comparator +
13	PD7 (AIN1)	Comparator negative input
14	PB0 (ICP1/CLKO)	Timer1 input capture, system clock output
15	PB1 (OC1A)	PWM Timer1
16	PB2 (OC1B/SS)	PWM Timer1, SPI slave select
17	PB3 (MOSI/OC2A)	SPI data out, PWM Timer2
18	PB4 (MISO)	SPI data in
19	PB5 (SCK)	SPI clock
20	AVCC	Analog power supply
21	AREF	ADC reference voltage
22	GND	Ground
23	PC0 (ADC0/SDA)	ADC ch0, I2C data
24	PC1 (ADC1/SCL)	ADC ch1, I2C clock
25	PC2 (ADC2)	ADC ch2
26	PC3 (ADC3)	ADC ch3
27	PC4 (ADC4/SDA)	ADC ch4, I2C data (alt)
28	PC5 (ADC5/SCL)	ADC ch5, I2C clock (alt)

Application Scenarios:In which products and applications isATmega328P-PU used

The ATmega328P-PU is the heart of the Arduino Uno, where it runs the Arduino bootloader and user sketches with access to digital I/O, analog inputs, PWM outputs, and serial communication through the board’s headers. In custom sensor nodes, the low 0.2mA active current at 1MHz/1.8V and 0.1µA power-down current enable coin-cell operation for years. For LED lighting control, the 6 PWM channels provide smooth dimming with 8-bit or 10-bit resolution. The I2C interface connects to EEPROM, RTC, and sensor peripherals with minimal wiring. The through-hole PDIP package is preferred for educational and hobbyist use, while the TQFP version (ATmega328P-AU) is used in production designs requiring surface-mount assembly.

Alternative Models:What chips are recommended as replacements for ATmega328P-PU

Model	Manufacturer	Key Difference
ATmega328PB-AU	Microchip	Enhanced version, 2× USART, 2× SPI, QTouch, TQFP-32
ATmega328P-AU	Microchip	Same die, TQFP-32 surface-mount package
ATtiny3217	Microchip	16KB Flash, smaller 20-pin, lower cost
PIC16F18877-I/P	Microchip	14KB Flash, 28-PDIP, PIC alternative