ATMEGA128A-MN - 8-bit AVR MCU, 128KB Flash 16MHz | Microchip
MPN: ATMEGA128A-MN ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $7.98 | $7.98 |
| 10 | $7.18 | $71.80 |
| 100 | $6.55 | $655.00 |
| 500 | $5.95 | $2,975.00 |
| 1,000 | $5.42 | $5,420.00 |
ATMEGA128A-MN Overview
An 8-bit microcontroller is a single-chip computer that integrates a processor core, program memory, data memory, and peripherals such as timers, UARTs, and ADCs onto one silicon die. Within the power-management and embedded-systems hierarchy, it belongs to the AVR family of enhanced RISC MCUs, positioned above simple 8-bit controllers like the ATtiny series and below 32-bit ARM-based parts, making it a workhorse for mid-complexity embedded control.
Key features include the AVR enhanced RISC architecture executing 133 powerful instructions - most in a single clock cycle - achieving throughput close to 1 MIPS per MHz. The flash supports read-while-write capability for in-system firmware updates, and 4KB of EEPROM retains calibration data through power cycles. The internal RC oscillator eliminates external crystals in timing-tolerant designs, and the part is rated to 105 degrees C for industrial environments.
Technically, the ATmega128A combines a 32-register general-purpose file directly connected to the ALU, four flexible timer/counters, a real-time counter, and multiple serial interfaces. Throughputs near 16 MIPS at 16 MHz let designers meet demanding control loops without migrating to 16- or 32-bit cores, preserving the large legacy AVR code base and toolchain investment.
Typical applications include industrial automation controllers, building automation and HVAC nodes, test and measurement instrumentation, and legacy ATmega103 board upgrades - the ATmega128A is 100% pin compatible with ATmega103 per the Microchip datasheet.
Design consideration: the 64-QFN exposed-pad package requires a solid ground vias array under the thermal pad; budget EEPROM write endurance and verify ISP programming pin access (MOSI/MISO/SCK/RESET) on your PCB for production programming.
This page synthesizes distributor pricing, drop-in alternatives, pinout guidance, and practical design notes not found in the manufacturer datasheet, based on data verified as of 2026-09-16.
Drop-in alternatives for ATMEGA128A-MN — 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 ATMEGA128A-MN (same form factor and footprint) — differing in Package, Supply Voltage Range, ADC Channels, EEPROM Size, Program Memory Size.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
ATMEGA128A-MNR
✅ Drop-In📋 Reference alternative (not in catalog)
ATMEGA1284P-MUR
✅ Drop-In✓ In Stock
Contact for price
View Datasheet →ATMEGA128-16MUR
✅ Drop-In✓ In Stock
$8.4 / Unit
View Datasheet →ATMEGA1281-16MUR
✅ Drop-In✓ In Stock
$8.78 / Unit
View Datasheet →ATMEGA128A-AU
✅ Drop-In✓ In Stock
$4.3 / Unit
View Datasheet →ATMEGA128A-MN Maximum Ratings & Electrical Characteristics
| Core | AVR 8-bit RISC |
| Program Memory Size | 128KB (64K x 16) FLASH |
| Program Memory Type | FLASH (read-while-write) |
| EEPROM Size | 4KB |
| SRAM Size | 4KB |
| Maximum Clock Frequency | 16 MHz |
| Number of I/O | 53 |
| General Purpose Working Registers | 32 |
| Oscillator Type | Internal |
| Package / Case | 64-QFN (9x9 mm), VFQFN exposed pad |
| Mounting Style | Surface Mount |
| Operating Temperature | -40C to +105C |
| Timers / Counters | Four flexible timer/counters plus real-time counter |
| Packaging | Tray |
| RoHS Status | Green (per Mouser listing) |
ATMEGA128A-MN 64-qfn (9x9 mm), vfqfn exposed pad Pin Configuration Guide
Pin configuration for ATMEGA128A-MN (64-qfn (9x9 mm), vfqfn exposed pad 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 ATMEGA128A-MN.
Refer to the datasheet for full pin configuration.
Typical Applications
ATMEGA128A-MN is suitable for 6 applications: Industrial Automation Controllers, Building Automation and HVAC, Test and Measurement Instrumentation, Legacy ATmega103 Board Upgrades, Embedded Communication Nodes, Consumer and Appliance Control Boards.
Industrial Automation Controllers
The ATMEGA128A-MN fits industrial control nodes that need serious program space without 32-bit complexity. Its 128KB flash accommodates large state machines, Modbus stacks, and HMI logic, while the -40C to +105C rating survives control-cabinet heat. Four flexible timer/counters generate PWM for motor drives and solenoids, and 53 GPIO lines interface sensors, relays, and limit switches directly. Typical designs run the MCU at 16 MHz for roughly 16 MIPS of headroom, with the internal oscillator reducing BOM cost where crystal precision is unnecessary. Place the device on a 5V-tolerant logic domain to simplify interfacing with legacy industrial I/O modules.
Recommended
Building Automation and HVAC
Thermostats, damper controllers, and zone-control boards benefit from the ATmega128A's 4KB EEPROM, which stores setpoints, schedules, and calibration tables through power cycles without external NVM. The 128KB flash holds communication stacks and logging firmware, while the real-time counter supports time-of-day scheduling from an external 32.768 kHz crystal. The 64-QFN 9x9 mm footprint fits dense wall-mounted PCBs, and the internal oscillator lets cost-sensitive designs drop the main crystal. Wide -40C to +105C operation covers rooftop equipment and boiler-room enclosures where ambient temperatures exceed consumer-grade limits regularly.
Recommended
Test and Measurement Instrumentation
Bench instruments, dataloggers, and sensor front-ends use the ATMEGA128A-MN's generous 128KB program space for menu systems, math routines, and multi-protocol output formatting. Single-cycle RISC execution at 16 MHz gives deterministic timing for measurement sequencing, and 4KB SRAM buffers sample arrays and string formatting. The 64-pin QFN exposes enough GPIO for keypad scanning, display driving, and multi-range relay switching in one controller. Firmware updates in the field are straightforward thanks to read-while-write flash boot-loader support, allowing feature upgrades on installed instruments without desoldering or socketed parts.
Recommended
Legacy ATmega103 Board Upgrades
The ATmega128A is 100% pin compatible with the ATmega103 according to the Microchip datasheet, making the ATMEGA128A-MN the standard migration path for maintaining installed ATmega103-based boards. The doubled 128KB flash removes the 103's code-size ceiling, and the refresh die keeps a mature product line in production without PCB changes. Microchip's application note 'Replacing ATmega103 by ATmega128A' documents fuse and register differences to address in firmware. For manufacturers servicing legacy industrial or medical equipment, this compatibility avoids costly board respins while restoring long-term component availability.
Recommended
Embedded Communication Nodes
Gateways, protocol converters, and wired sensor nodes exploit the ATmega128A's serial resources - multiple USARTs plus SPI and TWI (I2C) - to bridge RS-485 fieldbuses, RF modules, and local sensors in one controller. The 128KB flash holds dual protocol stacks simultaneously, and 4KB SRAM provides packet buffering for bursty traffic. Designs on this part commonly pair it with external transceivers and run the core at 5V for noise-margin advantage on long cable runs in factory or outdoor networks. The 105C rating and Green/RoHS compliance suit sealed, maintenance-free node enclosures deployed for years without service access.
Recommended
Consumer and Appliance Control Boards
Major appliances, power tools, and smart-home appliances use the ATMEGA128A-MN where UI complexity (menus, multiple languages, display drivers) outgrows smaller AVRs. The large flash stores rich graphics text tables and multiple localizations, while 53 GPIO drives seven-segment stacks, capacitive-touch front ends, and relay matrices directly. The internal oscillator and 9x9 mm QFN keep the controller BOM and footprint small for high-volume assembly, and the Green/RoHS-compliant finish satisfies global consumer-product environmental requirements. Volume production benefits from tray packaging feeding standard SMT pick-and-place lines without reel-conversion steps.
Recommended
Recommended Products Summary
Engineering reference data for ATMEGA128A-MN — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ATMEGA128A-MNR | ATMEGA1284P-MUR | ATMEGA128-16MUR | ATMEGA128A-AU |
|---|---|---|---|---|---|
| Package | 64-QFN (9x9 mm), exposed pad | 64-QFN (9x9 mm) - same | 64-QFN (9x9 mm) | 64-QFN (9x9 mm) | 64-TQFP |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Flash Memory | 128KB | 128KB | 128KB | 128KB | 128KB |
| SRAM | 4KB | 4KB | 16KB | 4KB | 4KB |
| Maximum Clock Frequency | 16 MHz | 16 MHz | 20 MHz | 16 MHz | 16 MHz |
| Packaging Media | Tray | Tape & Reel | Tape & Reel | Tape & Reel | Tray |
| Special Features | ATmega103 pin compatible, read-while-write flash, internal oscillator | Same features as ATMEGA128A-MN | picoPower, 20 MIPS, JTAG | Original ATmega128 die | Same die as MN in TQFP |
Key Differentiators
- ATmega103 pin compatibility for legacy board upgrades (vs ATMEGA1284P-MUR)
- Same-die family alternatives with identical flash (vs ATMEGA128A-MNR)
- Higher SRAM upgrade path within 64-pin AVR family (vs ATMEGA128-16MUR)
- Package choice flexibility (vs ATMEGA128A-AU)
Design Notes
The 64-QFN 9x9 mm package has a 0.5 mm lead pitch and an exposed center pad. Connect the exposed pad to a ground plane through an array of 4x4 or 5x5 vias (about 0.3 mm drill) to improve grounding and heat spreading. Use no-clean flux carefully - flux trapped under the QFN body is hard to remove. Check solder stencil apertures: 60-70% coverage on the thermal pad with segmented apertures reduces voiding during reflow.
Reserve the SPI ICSP signals (MOSI/MISO/SCK/RESET) on a standard 2x3 header for production programming, since in-circuit debugging and ICSP per Microchip's tool documentation use two device I/O pins plus reset. Also route JTAG (TCK/TMS/TDI/TDO) to test points or a header if boundary scan matters. After board spin, verify that these pins are not permanently loaded with circuitry that prevents entering programming mode - a common retrofit pitfall.
Decouple each VCC/AVCC pin pair with 100 nF ceramic capacitors placed within 2 mm of the pins, plus one bulk 4.7-10 uF per board region. When using the ADC, connect AVCC through an LC filter (ferrite bead plus 100 nF/10 uF) to reduce digital noise on conversions, and tie AREF to a 100 nF cap unless using an external reference. Estimated: at 5V, 16 MHz, and ~20 mA active current, dissipation is roughly 0.1 W - no thermal concern in the QFN, but verify with your actual I/O loading.
Flash speed depends on supply voltage: at 16 MHz the ATmega128A requires the upper voltage range per the datasheet speed-versus-voltage graph, so a 3.3V rail cannot run full-speed 16 MHz reliably. Fuse settings are a classic trap - disabling SPIEN via wrong fuse programming locks ICSP access. Also remember that EEPROM writes consume endurance cycles; add wear-leveling if logging writes at high frequency.
Compliance Information
Mouser listing describes the part as 'Green', Microchip's designation for RoHS-compliant and halogen-free. Full REACH and conflict-minerals status not stated in provided data.
