ATMEGA809-AU - 8-Bit AVR MCU 20MHz 8KB Flash | Microchip
MPN: ATMEGA809-AU ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $1.58 | $1.58 |
| 10 | $1.44 | $14.40 |
| 100 | $1.25 | $125.00 |
| 500 | $1.1 | $550.00 |
| 1,000 | $0.98 | $980.00 |
ATMEGA809-AU Overview
An 8-bit microcontroller is an integrated circuit that executes program code on a CPU with an 8-bit-wide data bus, combining flash program memory, SRAM data memory, EEPROM, peripherals, and clocking into a single chip. In the embedded-systems hierarchy, the ATMEGA809-AU sits within the megaAVR family of general-purpose MCUs, which in turn belongs to the broader microcontroller unit (MCU) category of semiconductor devices. Microcontrollers replace multi-chip processor-plus-peripheral designs, reducing board area, bill-of-materials cost, and system power consumption.
Key features include the megaAVR 0-series Core Independent Peripherals (CIPs), which include the Event System allowing peripherals to communicate directly without CPU intervention, intelligent analog modules, and advanced low-power features. Connectivity is provided by I2C (TWI), SPI, and UART/USART serial interfaces, supporting multi-drop sensor networks and host communication. Peripheral functions include Brown-out Detect/Reset and Power-on Reset for supply supervision, ensuring reliable startup and operation in noisy electrical environments.
Architecturally, the ATMEGA809-AU uses the AVR RISC core with a hardware multiplier, enabling single-cycle arithmetic for digital control and signal-processing tasks while executing code from 8 KB of flash. The 1 KB SRAM provides workspace for program variables and communication buffers, while the 256-byte EEPROM retains calibration data and configuration through power cycles. Supply supervision peripherals such as BOD keep the core within safe operating margins across the full voltage and temperature range.
Typical applications include industrial automation nodes, home-appliance control boards, IoT sensor endpoints, and motor-control or LED-lighting systems where an efficient 8-bit MCU with robust analog and safety supervision is required at low cost.
When designing with the ATMEGA809-AU, use the single-pin UPDI interface (shared with PORTF) for programming and debugging to minimize external tooling overhead, and configure Brown-out Detection to match the supply rail's droop characteristics. Decouple VDD pins with 100 nF ceramics placed close to the package.
This page synthesizes distributor pricing, drop-in family alternatives, pinout data, and practical design guidance not consolidated in the manufacturer datasheet, verified against DigiKey, Mouser, LCSC, and Microchip sources as of 2026-09-18.
Drop-in alternatives for ATMEGA809-AU — 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 ATMEGA809-AU (same form factor and footprint) — differing in Core Processor, Peripherals, Connectivity, Series, Number of I/O.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
ATMEGA1609-AU
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$1.15 / Unit
View Datasheet →ATMEGA3209-AU
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$1.06 / Unit
View Datasheet →ATMEGA4809-AU
✅ Drop-In ⚠️ 参数待验证📋 Reference alternative (not in catalog)
ATMEGA809-AFR
✅ Drop-In✓ In Stock
$1.55 / Unit
View Datasheet →ATMEGA1609-AFR
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$1.87 / Unit
View Datasheet →ATMEGA4809-AFR
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$1.36 / Unit
View Datasheet →ATMEGA809-AU Maximum Ratings & Electrical Characteristics
| Core Processor | AVR (8-bit) |
| Core Size | 8-Bit |
| Maximum Clock Frequency | 20 MHz |
| Flash Memory | 8 KB (8K x 8) |
| SRAM | 1 KB |
| EEPROM | 256 bytes |
| Connectivity | I2C, SPI, UART/USART |
| Peripherals | Brown-out Detect/Reset, Power-on Reset, Event System |
| Package | 48-TQFP (7x7 mm) |
| Mounting Type | Surface Mount |
| Series | megaAVR 0, Functional Safety (FuSa) |
| Program Memory Type | FLASH |
| Hardware Multiplier | Yes |
| RoHS Status | Compliant |
ATMEGA809-AU Pin Configuration
| Pin 1 | PA5 — General-purpose I/O, Port A bit 5 |
| Pin 2 | PA4 — General-purpose I/O, Port A bit 4 |
| Pin 3 | PA3 — General-purpose I/O, Port A bit 3 |
| Pin 4 | PA2 — General-purpose I/O, Port A bit 2 |
| Pin 5 | PA1 — General-purpose I/O, Port A bit 1 |
| Pin 6 | PA0 — General-purpose I/O, Port A bit 0 |
| Pin 7 | GND — Ground |
| Pin 8 | VDD — Power supply |
| Pin 9 | PA7 — General-purpose I/O, Port A bit 7 |
| Pin 10 | PA6 — General-purpose I/O, Port A bit 6 |
| Pin 11 | PB5 — General-purpose I/O, Port B bit 5 |
| Pin 12 | PB4 — General-purpose I/O, Port B bit 4 |
| Pin 13 | PB3 — General-purpose I/O, Port B bit 3 |
| Pin 14 | PB2 — General-purpose I/O, Port B bit 2 |
| Pin 15 | PB1 — General-purpose I/O, Port B bit 1 |
| Pin 16 | PB0 — General-purpose I/O, Port B bit 0 |
| Pin 17 | GND — Ground |
| Pin 18 | VDD — Power supply |
| Pin 19 | PC7 — General-purpose I/O, Port C bit 7 |
| Pin 20 | PC6 — General-purpose I/O, Port C bit 6 |
| Pin 21 | PC5 — General-purpose I/O, Port C bit 5 |
| Pin 22 | PC4 — General-purpose I/O, Port C bit 4 |
| Pin 23 | PC3 — General-purpose I/O, Port C bit 3 |
| Pin 24 | PC2 — General-purpose I/O, Port C bit 2 |
| Pin 25 | PC1 — General-purpose I/O, Port C bit 1 |
| Pin 26 | PC0 — General-purpose I/O, Port C bit 0 |
| Pin 27 | PD7 — General-purpose I/O, Port D bit 7 |
| Pin 28 | PD6 — General-purpose I/O, Port D bit 6 |
| Pin 29 | PD5 — General-purpose I/O, Port D bit 5 |
| Pin 30 | PD4 — General-purpose I/O, Port D bit 4 |
| Pin 31 | GND — Ground |
| Pin 32 | VDD — Power supply |
| Pin 33 | PD3 — General-purpose I/O, Port D bit 3 |
| Pin 34 | PD2 — General-purpose I/O, Port D bit 2 |
| Pin 35 | PD1 — General-purpose I/O, Port D bit 1 |
| Pin 36 | PD0 — General-purpose I/O, Port D bit 0 |
| Pin 37 | PE3 — General-purpose I/O, Port E bit 3 |
| Pin 38 | PE2 — General-purpose I/O, Port E bit 2 |
| Pin 39 | PE1 — General-purpose I/O, Port E bit 1 |
| Pin 40 | PE0 — General-purpose I/O, Port E bit 0 |
| Pin 41 | PF5 — General-purpose I/O, Port F bit 5 |
| Pin 42 | PF4 — General-purpose I/O, Port F bit 4 |
| Pin 43 | PF3 — General-purpose I/O, Port F bit 3 |
| Pin 44 | PF2 — General-purpose I/O, Port F bit 2 |
| Pin 45 | PF1 — General-purpose I/O, Port F bit 1 |
| Pin 46 | PF0 — General-purpose I/O, Port F bit 0 |
| Pin 47 | GND — Ground |
| Pin 48 | VDD — Power supply (UPDI is multiplexed on Port F per datasheet) |
Typical Applications
ATMEGA809-AU is suitable for 6 applications: Industrial Automation Nodes, Home Appliance Control, IoT Sensor Endpoints, Motor Control and Lighting, Educational and Hobbyist Platforms, Safety-Relevant Embedded Systems.
Industrial Automation Nodes
The ATMEGA809-AU fits industrial automation nodes where an 8-bit MCU must coordinate sensors and actuators over I2C, SPI, or UART/USART at up to 20 MHz. The megaAVR 0-series Core Independent Peripherals and Event System let timers, analog comparators, and communication modules react to events without CPU intervention, keeping deterministic timing in polling-heavy control loops. Brown-out Detect/Reset and Power-on Reset supervise the supply rail during brownouts caused by inductive loads or motor inrush. With 8 KB Flash and 1 KB SRAM, firmware for Modbus-style serial slaves or CAN-gateway glue logic fits comfortably. The 48-TQFP (7x7 mm) surface-mount package offers enough GPIO for optocoupler-driven I/O racks while remaining hand-solderable for prototype revisions.
Recommended
Home Appliance Control
Home-appliance control boards benefit from the ATMEGA809-AU's combination of low unit cost (about $1.58 in single quantities at LCSC as of 2026-09-18), robust supply supervision, and rich GPIO count in the 48-TQFP footprint. User interfaces with rotary encoders, seven-segment displays, and touch or mechanical buttons map directly onto PORTA-PORTF banks. The hardware multiplier accelerates PID control for temperature regulation in ovens and refrigerators at a 20 MHz core rate. UART/USART links to inverter or display modules, while EEPROM storage retains user settings and fault logs across power cycles. Brown-out Detect/Reset prevents corrupted EEPROM writes when mains sags occur, a common field failure in appliance electronics.
Recommended
IoT Sensor Endpoints
For battery- and mains-powered IoT sensor endpoints, the ATMEGA809-AU provides the megaAVR 0-series low-power architecture with intelligent analog and Core Independent Peripherals. The Event System allows a periodic timer to trigger ADC conversions and push results to a UART/USART radio link while the CPU sleeps, dramatically extending battery life. 8 KB Flash accommodates firmware including a serial protocol stack, and 256 bytes of EEPROM stores device identity and calibration constants. I2C and SPI interfaces connect humidity, pressure, and light sensors directly. Engineers can prototype rapidly using the MegaCoreX Arduino hardware package on GitHub, which explicitly supports the ATmega809, then deploy production code compiled with the AVR-GCC toolchain.
Recommended
Motor Control and Lighting
Motor-control and LED-lighting applications exploit the ATMEGA809-AU's 20 MHz AVR core with hardware multiplier for fast PID and PWM duty-cycle computation. Core Independent Peripherals can tie timers directly to output compare pins through the Event System, generating glitch-free PWM for BLDC phases or dimmable LED strings even during ISR latency. Intelligent analog blocks monitor current-sense inputs without external comparators in many designs. The 48-TQFP package exposes sufficient GPIO for gate-driver enables, fault inputs, and encoder interfaces, while UART/USART links the controller to a supervisory board. Brown-out supervision prevents runaway PWM outputs during supply transients, protecting power stages from shoot-through failures.
Recommended
Educational and Hobbyist Platforms
The ATMEGA809-AU is attractive for education and maker platforms because the open-source MegaCoreX Arduino hardware package on GitHub supports ATmega809, ATmega1609, ATmega3209, and ATmega4809 directly. Students program through the single-pin UPDI interface using low-cost Microchip SNAP or PICkit 4 tools, or via a serial bootloader, avoiding expensive debug probes. The AVR instruction set with hardware multiplier teaches both assembly fundamentals and C embedded development at a 20 MHz clock rate. The 48-TQFP (7x7 mm) package is solderable on simple two-layer boards, and 48 GPIO pins support robotics, sensor-lab, and display projects. Community documentation and forum threads on the Arduino forum lower the learning curve substantially.
Recommended
Safety-Relevant Embedded Systems
The ATMEGA809-AU is classified on DigiKey as a megaAVR 0-series Functional Safety (FuSa) microcontroller, making it a candidate for safety-relevant embedded systems such as machine-guard controllers, e-stop monitors, and building-safety sensing. Microchip provides safety-collateral documentation supporting IEC 61508-oriented developments for this family. The built-in Brown-out Detect/Reset and Power-on Reset reduce external supervision components, while the Event System enables redundant, CPU-independent signal paths that simplify diagnostic coverage arguments. With 8 KB Flash, safety firmware including self-test routines remains compact and auditable. Always obtain Microchip's current FuSa package and certificates to confirm qualification scope for your target safety integrity level before committing the design.
Recommended
Recommended Products Summary
Engineering reference data for ATMEGA809-AU — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ATMEGA1609-AU | ATMEGA3209-AU | ATMEGA4809-AU | ATMEGA809-AFR |
|---|---|---|---|---|---|
| Package | 48-TQFP (7x7) | 48-TQFP (7x7) - same | 48-TQFP (7x7) - same | 48-TQFP (7x7) - same | 48-TQFP (7x7) - same |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Core / Clock | AVR 8-bit, 20 MHz | AVR 8-bit, 20 MHz | AVR 8-bit, 20 MHz | AVR 8-bit, 20 MHz | AVR 8-bit, 20 MHz |
| Flash | 8 KB | 16 KB | 32 KB | 48 KB | 8 KB |
| SRAM | 1 KB | 2 KB | 4 KB | 6 KB | 1 KB |
| EEPROM | 256 bytes | 256 bytes | 256 bytes | 256 bytes | 256 bytes |
| Connectivity | I2C, SPI, UART/USART | I2C, SPI, UART/USART | I2C, SPI, UART/USART | I2C, SPI, UART/USART | I2C, SPI, UART/USART |
| Qualification | Standard, FuSa classification | Standard | Standard | Standard | Automotive grade |
Key Differentiators
- Lowest-cost entry point of the 48-pin megaAVR 0-series (vs ATMEGA4809-AU)
- Functional Safety (FuSa) product classification (vs ATMEGA1609-AU)
- Identical-die automotive option (vs ATMEGA809-AFR)
Design Notes
Decouple every VDD pin (pins 8, 18, 32, 48) with a 100 nF ceramic capacitor placed within 2 mm of the pin and returned to the nearest GND pin (7, 17, 31, 47). The 48-TQFP exposes a large center area - use it for a solid ground plane via array rather than a thermal pad. Route the UPDI pin trace to a standard 1x3 or Tag-Connect footprint on every production board; retrofitting a programming header after layout freeze is a common and costly mistake on megaAVR 0-series designs.
Configure Brown-out Detection (BOD) level to sit below the minimum operating voltage of your regulator's regulation band but above the MCU's minimum safe operating voltage for the chosen clock frequency, using the datasheet voltage-versus-frequency derating curve. Enable the BOD in continuous mode during flash/EEPROM writes and sampled mode elsewhere to reduce supply current. Neglecting BOD configuration is the most common cause of corrupted EEPROM contents on AVR designs operating near the voltage limit.
The megaAVR 0-series differs significantly from classic ATmega328P-era parts: fuse semantics, register maps, and the programming interface (UPDI instead of ISP) are all new, so legacy ISP programmers and classic Arduino bootloaders will not work. Use MPLAB X with SNAP, PICkit 4, or Atmel-ICE, or the community MegaCoreX package for Arduino IDE support. When migrating code from ATmega328P, budget time to re-map peripherals to the Event System rather than assuming register-level compatibility.
Compliance Information
RoHS compliant per current Microchip active-product status on DigiKey/LCSC listings; use ATMEGA809-AFR for AEC-Q100 automotive qualification. Formal REACH and halogen-free declarations should be obtained from Microchip's material declaration documents.
