ATMEGA329P-20AU - 20MHz 8-bit AVR MCU 32KB Flash TQFP-64
MPN: ATMEGA329P-20AU ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $7.42 | $7.42 |
| 10 | $6.68 | $66.80 |
| 100 | $5.95 | $595.00 |
| 500 | $5.32 | $2,660.00 |
| 1,000 | $4.71 | $4,710.00 |
ATMEGA329P-20AU Overview
An 8-bit AVR microcontroller is a Harvard-architecture MCU from Microchip's classic megaAVR family that executes one instruction per clock cycle, achieving throughputs approaching 1 MIPS per MHz. The megaAVR series sits within Microchip's broader 8-bit MCU portfolio (tinyAVR -> megaAVR -> XMEGA), serving as the mainstream workhorse for embedded control where deterministic real-time behavior, rich I/O, and ISP-based field upgradeability matter more than raw clock speed.
Key differentiating features include 54 general-purpose I/O lines, 32 general-purpose working registers, 131 powerful instructions (mostly single-cycle), a JTAG interface for on-chip debug, six PWM channels, a 10-bit ADC with up to 8 single-ended channels, two USARTs, a TWI (I2C) peripheral, and an SPI interface. The device supports an industrial operating temperature range of -40C to +85C and a supply voltage range of 2.7 V to 5.5 V at 10 MHz (4.5 V to 5.5 V required for the full 20 MHz operation indicated by the -20 speed grade).
Architecturally, the ATmega329P uses Microchip's picoPower technology with multiple sleep modes (Idle, ADC Noise Reduction, Power-save, Power-down, Standby, Extended Standby) and an advanced brown-out detector. The integrated QTouch library support enables capacitive touch sensing on any GPIO without external components, making it a popular choice for human-machine interface panels.
Typical applications include industrial control panels, LCD-display-driven HMI modules, white goods and appliance controllers, automotive body electronics (non-safety), USB device firmware using external PHY, and AVR-based data acquisition systems. The combination of substantial Flash, ample I/O, and built-in LCD-like peripheral support also makes it a common choice for educational development boards and OEM prototyping kits.
Designers should select the appropriate fuse configuration for clock source (internal 8 MHz RC vs external crystal) and verify the JTAG vs ISP pin usage does not conflict with application I/O assignments. The device uses standard SPI for ISP programming, allowing field firmware updates via a 6-pin header.
This page synthesizes distributor pricing, pin-compatible drop-in alternatives, and practical design notes - including comparison against the ATMEGA325P-20AU, ATMEGA3290P-20AU, and ATMEGA328P-AU family members - not found in the manufacturer datasheet alone.
Drop-in alternatives for ATMEGA329P-20AU — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with ATMEGA329P-20AU (same form factor and footprint) — differing in Package, Core Architecture, ADC, RoHS Status, LCD Controller.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
ATMEGA325P-20AUR
✅ Drop-In✓ In Stock
$4.11 / Unit
View Datasheet →ATMEGA329-16AU
✅ Drop-In✓ In Stock
$8.45 / Unit
View Datasheet →ATMEGA3290P-20AU
✅ Drop-In✓ In Stock
$9.62 / Unit
View Datasheet →ATMEGA325PA-AU
✅ Drop-In✓ In Stock
$4.95 / Unit
View Datasheet →ATMEGA329A-MUR
✅ Drop-In✓ In Stock
$3.61 / Unit
View Datasheet →ATMEGA329P-20AU Maximum Ratings & Electrical Characteristics
| Core Architecture | AVR (8-bit RISC, Harvard) |
| Instruction Set | 131 instructions, mostly single-cycle |
| Program Memory (Flash) | 32 KB (16K x 16), In-System Programmable with RWW |
| EEPROM | 1 KB |
| SRAM | 2 KB (2K x 8) |
| Maximum Clock Speed | 20 MHz |
| Throughput | Up to 20 MIPS at 20 MHz |
| Supply Voltage (Vcc) | 2.7 V to 5.5 V (10 MHz max below 4.5 V; 20 MHz requires 4.5-5.5 V) |
| General-Purpose I/O Pins | 54 |
| General-Purpose Working Registers | 32 |
| ADC | 10-bit, up to 8 single-ended channels |
| PWM Channels | 6 |
| Communication Peripherals | 2x USART, 1x TWI (I2C), 1x SPI (also ISP) |
| Debug Interface | JTAG (IEEE 1149.1 compliant) |
| Package | 64-pin TQFP (14x14 mm, 0.8 mm pitch) |
| Operating Temperature | -40C to +85C (industrial, -A suffix) |
| Mounting Type | Surface Mount |
| RoHS Status | Compliant (Pb-free / Green) |
| Power-Save Modes | Idle, ADC Noise Reduction, Power-save, Power-down, Standby, Extended Standby (picoPower) |
| QTouch Support | Yes (peripheral touch controller via library) |
ATMEGA329P-20AU Pin Configuration
| Pin 1 | GND — Ground |
| Pin 2 | PE0 — Port E bit 0 (PCINT8/ACO) |
| Pin 3 | PE1 — Port E bit 1 (PCINT9/ADC6) |
| Pin 4 | PE2 — Port E bit 2 (PCINT10/ADC7) |
| Pin 5 | PE3 — Port E bit 3 (PCINT11) |
| Pin 6 | PE4 — Port E bit 4 (PCINT12) |
| Pin 7 | PE5 — Port E bit 5 (PCINT13) |
| Pin 8 | PE6 — Port E bit 6 (PCINT14) |
| Pin 9 | PE7 — Port E bit 7 (PCINT15) |
| Pin 10 | VCC — Digital supply voltage |
| Pin 11 | GND — Ground |
| Pin 12 | PG0 — Port G bit 0 |
| Pin 13 | PG1 — Port G bit 1 |
| Pin 14 | XTAL2 — Crystal oscillator output |
| Pin 15 | XTAL1 — Crystal oscillator input |
| Pin 16 | RESET — Reset input (active low) |
| Pin 17 | PD0 — Port D bit 0 (RXD0/PCINT24) |
| Pin 18 | PD1 — Port D bit 1 (TXD0/PCINT25) |
| Pin 19 | PD2 — Port D bit 2 (RXD1/INT0/PCINT26) |
| Pin 20 | PD3 — Port D bit 3 (TXD1/INT1/PCINT27) |
| Pin 21 | PD4 — Port D bit 4 (OC1B/PCINT28) |
| Pin 22 | PD5 — Port D bit 5 (OC1A/PCINT29) |
| Pin 23 | PD6 — Port D bit 6 (OC2B/ICP/PCINT30) |
| Pin 24 | PD7 — Port D bit 7 (OC2A/PCINT31) |
| Pin 25 | PC0 — Port C bit 0 (SCL/PCINT16) |
| Pin 26 | PC1 — Port C bit 1 (SDA/PCINT17) |
| Pin 27 | PC2 — Port C bit 2 (TCK/PCINT18) |
| Pin 28 | PC3 — Port C bit 3 (TMS/PCINT19) |
| Pin 29 | PC4 — Port C bit 4 (TDO/PCINT20) |
| Pin 30 | PC5 — Port C bit 5 (TDI/PCINT21) |
| Pin 31 | PC6 — Port C bit 6 (TOSC1/PCINT22) |
| Pin 32 | PC7 — Port C bit 7 (TOSC2/PCINT23) |
| Pin 33 | VCC — Digital supply voltage |
| Pin 34 | GND — Ground |
| Pin 35 | PB0 — Port B bit 0 (SS/PCINT0) |
| Pin 36 | PB1 — Port B bit 1 (SCK/PCINT1) |
| Pin 37 | PB2 — Port B bit 2 (MOSI/PCINT2) |
| Pin 38 | PB3 — Port B bit 3 (MISO/PCINT3) |
| Pin 39 | PB4 — Port B bit 4 (OC0A/PCINT4) |
| Pin 40 | PB5 — Port B bit 5 (OC0B/PCINT5) |
| Pin 41 | PB6 — Port B bit 6 (OC1B/PCINT6) |
| Pin 42 | PB7 — Port B bit 7 (OC1A/OC0C/PCINT7) |
| Pin 43 | PF0 — Port F bit 0 (ADC0) |
| Pin 44 | PF1 — Port F bit 1 (ADC1) |
| Pin 45 | PF2 — Port F bit 2 (ADC2/ACMP0-) |
| Pin 46 | PF3 — Port F bit 3 (ADC3/ACMP0+) |
| Pin 47 | PF4 — Port F bit 4 (ADC4/TCK) |
| Pin 48 | PF5 — Port F bit 5 (ADC5/TMS) |
| Pin 49 | PF6 — Port F bit 6 (ADC6/TDO) |
| Pin 50 | PF7 — Port F bit 7 (ADC7/TDI) |
| Pin 51 | PA0 — Port A bit 0 (ADC8) |
| Pin 52 | PA1 — Port A bit 1 (ADC9) |
| Pin 53 | PA2 — Port A bit 2 (ADC10) |
| Pin 54 | PA3 — Port A bit 3 (ADC11) |
| Pin 55 | PA4 — Port A bit 4 (ADC12) |
| Pin 56 | PA5 — Port A bit 5 (ADC13) |
| Pin 57 | PA6 — Port A bit 6 (ADC14) |
| Pin 58 | PA7 — Port A bit 7 (ADC15) |
| Pin 59 | AVCC — Analog supply voltage |
| Pin 60 | AGND — Analog ground |
| Pin 61 | AREF — ADC reference voltage |
| Pin 62 | GND — Ground |
| Pin 63 | PG2 — Port G bit 2 |
| Pin 64 | PG3 — Port G bit 3 |
Typical Applications
ATMEGA329P-20AU is suitable for 7 applications: Industrial Control Panels, LCD-Driven HMI Modules, White Goods and Appliance Controllers, Automotive Body Electronics, USB Device Firmware (with External PHY), Educational Development Boards, Data Acquisition Systems.
Industrial Control Panels
The ATMEGA329P-20AU's 54 GPIO, 20 MHz throughput, and 32 KB Flash make it a strong fit for industrial control panels requiring multiple switch inputs, relay outputs, and indicator LEDs. Its picoPower sleep modes reduce quiescent current to microamps for battery-backed installations, and the JTAG interface enables on-board firmware debugging during panel commissioning. The 10-bit ADC with eight channels directly reads 4-20 mA sensor signals via shunt resistors without an external ADC, reducing BOM cost. Operate the part at 5 V for full 20 MHz performance; the industrial -40C to +85C temperature range matches factory floor requirements.
Recommended
LCD-Driven HMI Modules
The ATMEGA329P-20AU integrates an LCD controller capable of driving segment LCDs up to 4x40 segments directly, eliminating the need for an external LCD driver IC in HMI modules. Combined with the QTouch peripheral touch library, a single chip handles both display and capacitive button scanning on white goods, thermostats, and appliance front panels. The 32 KB Flash holds a full segment-LCD UI plus a small RTOS, while the 2 KB SRAM supports menu state and button debounce buffers. The 5 V supply rail common to LCD panels matches the part's 4.5-5.5 V operating range for 20 MHz operation.
Recommended
White Goods and Appliance Controllers
Washing machines, dishwashers, refrigerators, and ovens require deterministic real-time control of motors, valves, and heaters - exactly the domain of the ATMEGA329P-20AU. The AVR core's single-cycle instruction execution and 131 instructions deliver predictable interrupt latency for safety-critical loops, while the six PWM channels drive triac-controlled heater elements and variable-speed motor drives. The integrated 10-bit ADC reads thermistor and pressure-sensor inputs directly, and the TWI peripheral interfaces to EEPROM and RTC chips for non-volatile settings. Industrial -40C to +85C temperature grade handles under-cabinet heat in kitchen installations.
Recommended
Automotive Body Electronics
The ATMEGA329P-20AU serves in non-safety automotive body applications such as seat controllers, mirror adjusters, lighting modules, and accessory multiplexers where 54 GPIO and CAN-equivalent bit-banged protocols meet the I/O density requirement. The 20 MHz core handles LIN slave protocol stacks in firmware, and the wide 2.7-5.5 V supply tolerates automotive 12 V rails after regulation. Note that this part is not AEC-Q100 qualified; safety-critical ADAS applications require automotive-grade parts like ATmega328PB-AUR or PIC16 variants from the Site MPN list.
Recommended
USB Device Firmware (with External PHY)
Although the ATMEGA329P-20AU lacks an integrated USB controller, its SPI peripheral paired with external USB transceiver ICs (e.g., MAX3420E SPI-to-USB bridge) enables cost-optimized USB device applications such as custom HID peripherals, test instruments, and data loggers. The 20 MHz core delivers the throughput required for full-speed USB 12 Mbps bit-banging via external interrupt-driven firmware on PDI/PDO pins, and the 32 KB Flash accommodates USB stacks. Two USARTs allow simultaneous USB-to-serial and RS-485 bridging.
Recommended
Educational Development Boards
The ATMEGA329P-20AU is a popular MCU for educational AVR development boards thanks to its 54 GPIO headers, JTAG debug port, generous 32 KB Flash for student projects, and full ISP programming via SPI. It runs the open-source AVR-GCC toolchain, supports WinAVR, Atmel Studio, and the modern Microchip MPLAB X IDE with AVR-DUDE for in-system programming. The picoPower sleep modes teach energy-efficient embedded design, while the ADC, PWM, TWI, and SPI peripherals cover a complete undergraduate embedded systems curriculum in a single chip.
Recommended
Data Acquisition Systems
With its 10-bit ADC offering up to eight single-ended input channels, the ATMEGA329P-20AU captures multi-sensor data in compact SCADA and environmental monitoring systems. The 20 MHz core runs averaging filters and small FFTs in real time at 1 kHz sample rates, and the 2 KB SRAM buffers one-second windows before writing to external SPI Flash or SD cards via the SPI peripheral. The TWI/I2C bus interfaces to digital temperature sensors and RTC chips, while the USART streams data to a host PLC or cellular modem. The -40C to +85C industrial range supports outdoor enclosure deployments.
Recommended
Recommended Products Summary
Engineering reference data for ATMEGA329P-20AU — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ATMEGA325P-20AU | ATMEGA329-16AU | ATMEGA3290P-20AU | ATMEGA325PA-AU | ATMEGA329A-MUR |
|---|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | TQFP-64 (14x14 mm) | TQFP-64 (14x14 mm) - same | TQFP-64 (14x14 mm) - same | TQFP-64 (14x14 mm) - same | TQFP-64 (14x14 mm) - same | TQFP-64 (14x14 mm) - same |
| Max Clock Speed | 20 MHz | 20 MHz | 16 MHz | 20 MHz | 20 MHz | 20 MHz |
| Flash | 32 KB | 32 KB | 32 KB | 32 KB | 32 KB | 32 KB |
| SRAM | 2 KB | 2 KB | 2 KB | 2 KB | 2 KB | 2 KB |
| EEPROM | 1 KB | 1 KB | 1 KB | 1 KB | 1 KB | 1 KB |
| GPIO Count | 54 | 54 | 54 | 100 | 54 | 54 |
| Supply Voltage | 2.7 V to 5.5 V | 2.7 V to 5.5 V | 2.7 V to 5.5 V | 2.7 V to 5.5 V | 1.8 V to 5.5 V | 1.8 V to 5.5 V |
| LCD Controller | Yes | No | Yes | Yes | No | Yes |
| Operating Temperature | -40C to +85C | -40C to +85C | -40C to +85C | -40C to +85C | -40C to +85C | -40C to +85C |
Key Differentiators
- Integrated segment LCD controller for HMI panels (vs ATMEGA325P-20AU)
- Higher GPIO count (100) on pin-compatible footprint (vs ATMEGA3290P-20AU)
- Faster 20 MHz operation versus 16 MHz older revision (vs ATMEGA329-16AU)
- QTouch peripheral touch library support (vs PIC16C64A-20/PQ)
Design Notes
The ATMEGA329P-20AU supports 2.7 V to 5.5 V operation, but full 20 MHz throughput requires Vcc >= 4.5 V per the datasheet speed-grade table. At 3.3 V operation the core must be clocked at 10 MHz or below. Decouple each Vcc/GND pair with a 100 nF ceramic capacitor placed within 5 mm of the pin, and add a single 10 uF bulk capacitor near the package. The AVCC pin must be tied to Vcc through a ferrite bead or 10 ohm resistor for analog noise isolation, with a 100 nF decoupling cap to AGND. The AREF pin should be bypassed with 100 nF to AGND when using internal ADC reference.
Place a 6-pin ISP header (MOSI, MISO, SCK, RESET, Vcc, GND) accessible on the board for in-system programming without JTAG. Connect the 100 nF RESET decoupling capacitor directly between the RESET pin and GND, placed within 5 mm to suppress noise-induced resets. For JTAG use, route TCK, TMS, TDI, TDO traces with 1k pull-ups on TDI/TMS/TCK if the JTAG adapter does not provide them. Keep crystal traces short (<10 mm) and symmetric, with the load capacitors (typically 12-22 pF) close to the XTAL1/XTAL2 pins to ensure stable oscillation across the -40C to +85C range.
Do not exceed the absolute maximum Vcc of 6.0 V or inject signals on any pin while Vcc is below 1.5 V (latch-up risk). The brown-out detector (BOD) must be enabled via fuses to prevent code corruption during brown-out events; the default BOD threshold may be inappropriate for 3.3 V operation and should be reprogrammed. The JTAG port shares pins with PC2-PC5; if these pins are needed for application I/O, program the JTAGEN fuse to disabled. Avoid routing high-frequency signals near the AREF pin to minimize ADC noise pickup. When migrating firmware from ATMEGA328P-AU, verify that the extended peripheral registers (LCD, additional USART) are properly initialized.
Compliance Information
RoHS compliant per Microchip product page; not AEC-Q100 qualified (use ATmega328PB-AUR or PIC automotive parts for AEC-Q100). Lead-free / Green packaging per Microchip part numbering convention. Conflict-mineral compliance per Microchip corporate statement.
