ATMEGA2561-16AUR - 8-bit AVR MCU 256KB 16MHz | Microchip
MPN: ATMEGA2561-16AUR β Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $21.31 | $21.31 |
| 10 | $19.98 | $199.80 |
| 100 | $18.45 | $1,845.00 |
| 500 | $17.2 | $8,600.00 |
| 1,000 | $15.98 | $15,980.00 |
ATMEGA2561-16AUR Overview
A microcontroller unit (MCU) is a single integrated circuit that combines a processor core, program memory (Flash), data memory (SRAM and EEPROM), and peripheral interfaces such as UART, SPI, and I2C. Within the semiconductor hierarchy, the ATmega2561 sits in the 8-bit microcontroller category under embedded processors, a superset that includes MCUs, MPUs, and DSPs. 8-bit AVRs remain widely used where deterministic execution, simple toolchains, and 5V tolerance matter.
Key features include the AVR enhanced RISC architecture with mostly single-cycle instruction execution, six flexible timer/counters with compare modes and PWM, four USARTs for serial communication, a byte-oriented 2-wire serial interface (TWI/I2C), a master/slave SPI interface, an 8-channel 10-bit ADC, a programmable watchdog timer with separate on-chip oscillator, an on-chip analog comparator, and interrupt and wake-up on pin change for low-power designs. The ATmega2561 is the 64-pin member of the ATmega640/1280/1281/2560/2561 family, sharing peripherals with the 100-pin ATmega2560 in a more compact footprint.
The 16 MHz -16 speed grade delivers up to 16 MIPS throughput, while the AVR Harvard architecture with 32 registers gives exceptionally efficient compiled C code. The 256 KB Flash supports self-programming via ISP bootloader, and the 4 KB EEPROM retains calibration data through power cycles. Operating voltage is 4.5V to 5.5V with industrial temperature range of -40C to +85C for the 'I' suffix.
Typical applications include industrial automation controllers, motor control panels, building automation, embedded instrumentation, and legacy 5V board designs requiring pin-compatible upgrades from ATmega128 designs.
For reliable design, use the internal PLL-free clocking path, keep XTAL1/XTAL2 traces short, and budget the watchdog oscillator tolerance when relying on WDT reset timing.
This page synthesizes distributor pricing, drop-in alternatives, comparison tables, and practical design notes not found in the manufacturer datasheet.
Drop-in alternatives for ATMEGA2561-16AUR β 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 ATMEGA2561-16AUR (same form factor and footprint) β differing in Flash Memory, EEPROM, Package, SRAM, General Purpose I/O.
Quick Comparison Tool β Select alternative parts for side-by-side comparison:
ATMEGA2561-16AI
β Drop-Inπ Reference alternative (not in catalog)
ATMEGA1281-16AU
β Drop-Inβ In Stock
$8.27 / Unit
View Datasheet βATMEGA2561V-8AU
β Drop-Inπ Reference alternative (not in catalog)
ATMEGA2561-16AUR Maximum Ratings & Electrical Characteristics
| Core Architecture | 8-bit AVR RISC |
| Flash Memory | 256 KB (128K x 16), ISP programmable |
| SRAM | 8 KB |
| EEPROM | 4 KB |
| Maximum CPU Speed | 16 MHz |
| Throughput | 16 MIPS at 16 MHz |
| Operating Voltage Range | 4.5 V to 5.5 V |
| General Purpose I/O | 54 I/O lines |
| Working Registers | 32 general purpose registers |
| Timer/Counters | Six flexible timer/counters with compare modes and PWM |
| USART | Four programmable serial USART |
| ADC | 8-channel, 10-bit |
| Serial Interfaces | SPI, TWI (I2C-compatible 2-wire) |
| Analog Comparator | On-chip, 1 channel |
| Watchdog Timer | Programmable, with separate on-chip oscillator |
| Operating Temperature | -40C to +85C (industrial) |
| Package | 64-TQFP (14 x 14 mm) |
| Mounting Type | Surface Mount |
| Real-Time Counter | Yes, with separate oscillator (TOSC1/TOSC2) |
| Pin Change Interrupt | Interrupt and wake-up on pin change |
| RoHS Status | Compliant |
ATMEGA2561-16AUR 64-tqfp (14 x 14 mm) Pin Configuration Guide
Pin configuration for ATMEGA2561-16AUR (64-tqfp (14 x 14 mm) package). This digital IC includes GPIO, communication interfaces (UART, SPI, I2C), and power pins. Refer to the manufacturer datasheet for alternate pin functions and configuration options. Essential for embedded system design and PCB layout.
No detailed pinout data available for ATMEGA2561-16AUR.
Refer to the datasheet for full pin configuration.
Typical Applications
ATMEGA2561-16AUR is suitable for 6 applications: Industrial Automation Controllers, Motor Control and Drives, Building Automation and HVAC, Embedded Instrumentation and Test Equipment, 5V Legacy Board Redesign and Obsolescence Recovery, Security and Access Control Systems.
Industrial Automation Controllers
The ATMEGA2561-16AUR fits industrial automation controllers because its 5V operation provides high noise margin on factory floors, its industrial -40C to +85C temperature grade survives panel environments, and its 256 KB Flash accommodates protocol stacks, state machines, and firmware-update bootloaders without external memory. Four USARTs allow simultaneous Modbus RTU, HMI, and sensor links, while SPI and TWI (I2C) connect ADCs, RTCs, and EEPROM peripherals. Six timer/counters generate coordinated PWM channels for actuators and conveyors, and the independent-oscillator watchdog guarantees recovery from field upsets, a prerequisite for 24/7 unattended equipment.
Recommended
Motor Control and Drives
For motor control, the ATMEGA2561-16AUR offers six timer/counters with compare modes and PWM outputs sufficient for closed-loop DC and stepper drive firmware, with the 16 MHz clock giving 16 MIPS of control-loop headroom at the -16 speed grade. The 8-channel 10-bit ADC samples current shunts, back-EMF, and position potentiometers; the on-chip analog comparator supports zero-cross detection in sensorless schemes. The 5V rail matches discrete gate-driver logic levels directly, and the watchdog timer with separate oscillator provides the fail-safe shutdown path that drive designers require for thermal or stall fault recovery.
Recommended
Building Automation and HVAC
Building automation nodes benefit from the ATMEGA2561-16AUR's combination of 4 KB EEPROM for storing calibration setpoints and network credentials through power cycles, 256 KB Flash for BACnet-lite or proprietary protocol handling, and TWI (I2C) plus SPI for sensors, displays, and RTCs. Four USARTs interface with RS-485 transceivers, GSM modems, and service ports simultaneously. The 5V noise margin suits long wire runs in electrically noisy mechanical rooms, while interrupt and wake-up on pin change, together with sleep modes, trims average consumption in thermostat and damper-actuator applications that idle most of the time.
Recommended
Embedded Instrumentation and Test Equipment
Bench and portable instrumentation leverage the ATMEGA2561-16AUR's 10-bit ADC for measurement front ends, its precise timer/counter capture inputs (ICP) for frequency and pulse-width measurement, and its generous Flash for menus, logging, and USB-serial update firmware. The real-time counter with its dedicated TOSC1/TOSC2 32 kHz crystal keeps timestamps accurate across mains cycles. Four USARTs let one MCU talk to a display, a printer, and a host PC concurrently. The 32-register AVR core yields compact, deterministic C code, which simplifies validation documentation for measurement-grade products.
Recommended
5V Legacy Board Redesign and Obsolescence Recovery
Many legacy 5V PCBs built around ATmega128 or ATmega8515 MCUs face end-of-life pressure. The ATMEGA2561-16AUR is the natural upgrade target: it runs on the same 5V rail, uses the same AVR toolchain and ISP programming headers, and its 256 KB Flash provides headroom so old code merges with new features without a memory crisis. Designers replacing discontinued parts can port firmware with minimal changes because the peripheral register model is common across the ATmega family. Active, in-stock availability at DigiKey, Mouser, and LCSC makes it a durable long-term fit for service-life extensions.
Recommended
Security and Access Control Systems
Access-control panels and gate controllers use the ATMEGA2561-16AUR's 54 GPIO lines to drive keypads, relays, door sensors, and indicators from a single 5V MCU, with pin-change interrupts waking the device on any user interaction for responsive, low-average-power operation. The 4 KB EEPROM stores credential databases and event logs through outages, while 256 KB Flash hosts encryption routines and audit firmware. Four USARTs connect RFID readers, GSM notification modems, and RS-485 supervision buses simultaneously, and the watchdog timer ensures doors fail to a defined safe state after any firmware fault.
Recommended
Recommended Products Summary
Engineering reference data for ATMEGA2561-16AUR β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ATMEGA2561-16AI | ATMEGA1281-16AU | ATMEGA2561V-8AU |
|---|---|---|---|---|
| Package | 64-TQFP (14x14 mm) | 64-TQFP (14x14 mm) - same | 64-TQFP (14x14 mm) - same | 64-TQFP (14x14 mm) - same |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Flash Memory | 256 KB | 256 KB | 128 KB | 256 KB |
| SRAM | 8 KB | 8 KB | 8 KB | 8 KB |
| EEPROM | 4 KB | 4 KB | 4 KB | 4 KB |
| Maximum Clock Speed | 16 MHz | 16 MHz | 16 MHz | 8 MHz |
| Operating Voltage | 4.5 V to 5.5 V | 4.5 V to 5.5 V | 4.5 V to 5.5 V | 1.8 V to 5.5 V |
| General Purpose I/O | 54 I/O lines | 54 I/O lines | 54 I/O lines | 54 I/O lines |
| Grade / Temperature | Industrial, -40C to +85C | Automotive grade | Industrial | Industrial |
Key Differentiators
- Full 256 KB Flash in a compact 64-pin footprint (vs ATMEGA1281-16AU)
- 54 I/O lines with 86-I/O sibling upgrade path (vs ATMEGA2560-16AU)
- 5V noise-margin operation at 16 MHz (vs ATMEGA2561V-8AU)
Design Notes
The ATMEGA2561-16AUR requires 4.5V to 5.5V for the -16 speed grade. Decouple each VCC pin with 100 nF ceramic capacitors placed within a few millimeters of the pins, plus one bulk 10 uF per supply domain. The AVR core has significant di/dt on clock edges, so a solid ground plane under the 64-TQFP is mandatory. If the board also hosts relays or motor drivers, isolate the MCU 5V rail from inductive load rails with an LC filter or ferrite bead to prevent brown-out resets during switching events.
Keep XTAL1/XTAL2 crystal traces under 10 mm and guard them with ground pour; the AVR oscillator is sensitive to coupled noise which can cause startup failure, especially at 16 MHz. The real-time counter crystal on TOSC1/TOSC2 should use a 32.768 kHz watch crystal with short traces. Route the four USART and SPI buses away from the crystal area. If using JTAG for debug, reserve the PC2-PC5 pins accordingly and add a standard 10-pin AVR JTAG header. Test the PEN (programming enable) pin tie-off per the datasheet programming section.
The most common migration error is treating ATmega2560 (100-pin) code as directly portable to the 64-pin ATmega2561: the 2561 has fewer I/O lines (54 vs 86), so pin assignments for ports absent on the 2561 must be remapped. Second, EEPROM writes at high frequency will wear the 4 KB EEPROM - implement wear leveling or throttle writes. Third, relying on the watchdog's separate oscillator for precise timing is invalid: its frequency has wide tolerance, so use it only as a fail-safe reset, not as a time base.
Compliance Information
Distributor listings for the -AUR suffix indicate RoHS-compliant, lead-free construction. For automotive AEC-Q100-qualified supply, use the ATMEGA2561-16AI variant. REACH, halogen-free, and conflict-minerals statuses were not stated in the provided data.