ATMEGA128L-8AI - 8-bit AVR MCU 8MHz 128KB TQFP-64 | Microchip
MPN: ATMEGA128L-8AI ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $9.85 | $9.85 |
| 10 | $8.95 | $89.50 |
| 100 | $7.98 | $798.00 |
| 500 | $7.25 | $3,625.00 |
| 1,000 | $6.6 | $6,600.00 |
ATMEGA128L-8AI Overview
An 8-bit microcontroller (MCU) is a self-contained computing chip integrating a processor core, program memory, data memory, and peripherals such as timers, UARTs, SPI, I2C, and ADC on a single die. MCUs sit at the device level of the embedded systems hierarchy: semiconductor -> integrated circuit -> embedded processor -> microcontroller, and are the workhorses of industrial control, instrumentation, and consumer electronics.
Key features of the ATmega128 include the advanced AVR RISC architecture with 133 mostly single-cycle instructions, 32 general-purpose working registers, throughput approaching 1 MIPS per MHz, and a JTAG interface for on-chip debugging and boundary-scan. The chip also integrates two 8-bit timers, two 16-bit timers, two USARTs, SPI, TWI (I2C), and an analog comparator, giving designers a complete peripheral set without external glue logic.
Architecturally, the ATmega128 uses a Harvard structure with separate program and data buses, allowing instruction fetch and data access to occur in the same clock cycle. Self-programming Flash enables in-system field updates through boot-loader firmware, while the byte-addressable EEPROM retains calibration data through power cycles. Power management modes (idle, power-down, power-save) reduce consumption for battery-operated designs.
Typical applications include industrial automation controllers, building and HVAC control, metering, battery-powered instrumentation, and legacy embedded designs requiring large 128KB program memory at modest clock rates.
Design consideration: choose the -8AI (8MHz, industrial) over the -16AI variant when operating below 5.5V or when power budget matters; verify that the ATmega128L flash erase/write cycles at low voltage match your end-of-life update plans.
This page synthesizes distributor availability data, same-package drop-in alternatives, and practical design notes not found in the manufacturer datasheet.
Drop-in alternatives for ATMEGA128L-8AI — 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 ATMEGA128L-8AI (same form factor and footprint) — differing in Timers/Counters, Package, Operating Temperature, Flash Memory, SRAM.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
ATMEGA128-16AI
✅ Drop-In✓ In Stock
$5.9 / Unit
View Datasheet →ATMEGA128-16AN
✅ Drop-In✓ In Stock
$7.44 / Unit
View Datasheet →ATMEGA128L-8AU
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$23.49 / Unit
View Datasheet →ATMEGA1284-AUR
✅ Drop-In✓ In Stock
$4.61 / Unit
View Datasheet →ATMEGA1284P-MUR
✅ Drop-In✓ In Stock
Contact for price
View Datasheet →ATMEGA1281V-8AUR
✅ Drop-In✓ In Stock
$4.4 / Unit
View Datasheet →ATMEGA128L-8AI Maximum Ratings & Electrical Characteristics
| Core | AVR 8-bit RISC |
| Program Memory Size | 128KB (64K x 16) Flash |
| Program Memory Type | In-System Programmable FLASH |
| RAM Size | 4K x 8 SRAM |
| EEPROM Size | 4KB |
| Maximum Clock Speed | 8MHz |
| Supply Voltage Range | 2.7V to 5.5V |
| MIPS Throughput | Up to 8 MIPS at 8MHz (approx. 1 MIPS/MHz) |
| ADC | 8-channel 10-bit |
| Timers | Two 8-bit, two 16-bit |
| Communication Interfaces | 2x USART, SPI, TWI (I2C) |
| Debug Interface | JTAG (on-chip debug and boundary scan) |
| Operating Temperature | -40C to +85C (industrial, A grade) |
| Package | 64-TQFP (14x14 mm) |
| Mounting Type | Surface Mount |
| Number of I/O | 53 programmable I/O lines |
ATMEGA128L-8AI Pin Configuration
| Pin 1 | PEN — Programming enable for serial programming |
| Pin 2 | PE0 (RXD0/PDI) — USART0 receive / SPI programming data in |
| Pin 3 | PE1 (TXD0/PDO) — USART0 transmit / SPI programming data out |
| Pin 4 | PE2 (XCK0/AIN0) — USART0 clock / analog comparator 0 input |
| Pin 5 | PE3 (AIN1/OC3A) — Analog comparator 1 input / Timer3 output compare A |
| Pin 6 | PE4 (OC3B/INT4) — Timer3 output compare B / external interrupt 4 |
| Pin 7 | PE5 (OC3C/INT5) — Timer3 output compare C / external interrupt 5 |
| Pin 8 | PE6 (T3/INT6) — Timer3 clock input / external interrupt 6 |
| Pin 9 | PE7 (ICP3/INT7) — Timer3 input capture / external interrupt 7 |
| Pin 10 | VCC — Digital supply voltage |
| Pin 11 | GND — Ground |
| Pin 12 | PG0 (WR) — External memory write strobe / GPIO |
| Pin 13 | PG1 (RD) — External memory read strobe / GPIO |
| Pin 14 | PC0 (A8) — External memory address bit 8 / GPIO |
| Pin 15 | PC1 (A9) — External memory address bit 9 / GPIO |
| Pin 16 | PC2 (A10) — External memory address bit 10 / GPIO |
| Pin 17 | PC3 (A11) — External memory address bit 11 / GPIO |
| Pin 18 | PC4 (A12) — External memory address bit 12 / GPIO |
| Pin 19 | PC5 (A13) — External memory address bit 13 / GPIO |
| Pin 20 | PC6 (A14) — External memory address bit 14 / GPIO |
| Pin 21 | PC7 (A15) — External memory address bit 15 / GPIO |
| Pin 22 | AREF — ADC reference voltage |
| Pin 23 | AGND — Analog ground |
| Pin 24 | AVCC — ADC and Port F supply voltage |
| Pin 25 | PF0 (ADC0) — ADC input 0 / GPIO |
| Pin 26 | PF1 (ADC1) — ADC input 1 / GPIO |
| Pin 27 | PF2 (ADC2) — ADC input 2 / GPIO |
| Pin 28 | PF3 (ADC3) — ADC input 3 / GPIO |
| Pin 29 | PF4 (ADC4/TCK) — ADC input 4 / JTAG test clock |
| Pin 30 | PF5 (ADC5/TMS) — ADC input 5 / JTAG test mode select |
| Pin 31 | PF6 (ADC6/TDO) — ADC input 6 / JTAG test data out |
| Pin 32 | PF7 (ADC7/TDI) — ADC input 7 / JTAG test data in |
| Pin 33 | GND — Ground |
| Pin 34 | VCC — Digital supply voltage |
| Pin 35 | PA0 (AD0) — External memory address/data bit 0 / GPIO |
| Pin 36 | PA1 (AD1) — External memory address/data bit 1 / GPIO |
| Pin 37 | PA2 (AD2) — External memory address/data bit 2 / GPIO |
| Pin 38 | PA3 (AD3) — External memory address/data bit 3 / GPIO |
| Pin 39 | PA4 (AD4) — External memory address/data bit 4 / GPIO |
| Pin 40 | PA5 (AD5) — External memory address/data bit 5 / GPIO |
| Pin 41 | PA6 (AD6) — External memory address/data bit 6 / GPIO |
| Pin 42 | PA7 (AD7) — External memory address/data bit 7 / GPIO |
| Pin 43 | PB0 (SS) — SPI slave select / GPIO |
| Pin 44 | PB1 (SCK) — SPI serial clock / GPIO |
| Pin 45 | PB2 (MOSI) — SPI master output / GPIO |
| Pin 46 | PB3 (MISO) — SPI master input / GPIO |
| Pin 47 | PB4 (OC0) — Timer0 output compare / GPIO |
| Pin 48 | PB5 (OC1A) — Timer1 output compare A / GPIO |
| Pin 49 | PB6 (OC1B) — Timer1 output compare B / GPIO |
| Pin 50 | PB7 (OC2/OC1C) — Timer2 output compare / Timer1 output compare C / GPIO |
| Pin 51 | RESET — Reset input (active low) |
| Pin 52 | VCC — Digital supply voltage |
| Pin 53 | GND — Ground |
| Pin 54 | XTAL2 — Crystal oscillator output |
| Pin 55 | XTAL1 — Crystal oscillator input / external clock |
| Pin 56 | PD0 (SCL/INT0) — TWI clock / external interrupt 0 |
| Pin 57 | PD1 (SDA/INT1) — TWI data / external interrupt 1 |
| Pin 58 | PD2 (TXD1/INT2) — USART1 transmit / external interrupt 2 |
| Pin 59 | PD3 (RXD1/INT3) — USART1 receive / external interrupt 3 |
| Pin 60 | PD4 (ICP1) — Timer1 input capture / GPIO |
| Pin 61 | PD5 (XCK1) — USART1 external clock / GPIO |
| Pin 62 | PD6 (T1) — Timer1 external clock input / GPIO |
| Pin 63 | PD7 (T2) — Timer2 external clock input / GPIO |
| Pin 64 | PG2 (ALE) — External memory address latch enable / GPIO |
Typical Applications
ATMEGA128L-8AI is suitable for 6 applications: Industrial Automation Controllers, Battery-Powered Metering and Instrumentation, Building and HVAC Control, Legacy Embedded Design Maintenance, IoT Sensor Nodes and Gateways, Test Equipment and Educational Systems.
Industrial Automation Controllers
The ATMEGA128L-8AI fits industrial automation nodes because its 128KB Flash accommodates large state machines and protocol stacks, while 4KB SRAM buffers sensor data and communication frames. Two USARTs and TWI (I2C) let a single chip bridge field devices to a Modbus or custom serial backbone, and the 53 I/O lines directly drive relays, optocouplers, and status LEDs. The -40C to +85C industrial grade ensures reliable cabinet operation, and the external memory interface (ports A and C) can extend RAM for data logging. Because throughput reaches roughly 1 MIPS per MHz at 8MHz, control loops in the millisecond range are comfortably handled without a faster, power-hungry processor.
Recommended
Battery-Powered Metering and Instrumentation
In battery-powered meters, the ATmega128L low-voltage grade (2.7V to 5.5V) runs directly from a 3V lithium cell, eliminating boost-converter cost and quiescent drain. The 8-channel 10-bit ADC digitizes multiple sensor channels, and the byte-addressable 4KB EEPROM stores calibration constants across battery replacement. Sleep modes cut consumption between measurements, and the ~1 MIPS/MHz efficiency allows the clock to be scaled down for compute-light tasks. With 128KB of self-programming Flash, firmware field updates over the meter's serial link are possible via boot-loader code, extending deployed product lifetime. The industrial temperature rating also suits outdoor meter enclosures exposed to seasonal extremes.
Recommended
Building and HVAC Control
HVAC controllers benefit from the ATMEGA128L-8AI's balance of memory and peripherals: TWI and SPI manage temperature, humidity, and pressure sensor networks, timers generate PWM for fan and valve actuation, and the ADC reads thermistor bridges directly. The 128KB program space holds PID libraries, scheduling logic, and communications (Modbus RTU over USART) simultaneously. The 64-TQFP's 53 I/O lines interface keypads, displays, and actuator relays without port expanders. Its 8MHz operation is ample for second-level HVAC loop timing, while low-voltage tolerance allows a shared 3.3V logic rail. The JTAG interface simplifies production debugging of control firmware in the panel during commissioning.
Recommended
Legacy Embedded Design Maintenance
Many long-life products were designed around the ATmega128 and still require maintenance builds. The ATMEGA128L-8AI remains the exact drop-in for these PCBs: same TQFP-64 footprint, same fuse set, same instruction set, so existing firmware binaries reflash without modification. The -8AI suffix preserves the industrial temperature range that the original commercial -8AU did not, improving robustness at zero PCB cost. This makes it ideal for spare-part refresh programs in factory equipment, elevators, and lab instruments where a redesign to a modern MCU would trigger full requalification. Availability from 16 distributors, per Octopart, keeps maintenance lines running without long lead times.
Recommended
IoT Sensor Nodes and Gateways
For wired IoT nodes, the ATMEGA128L-8AI provides enough Flash to embed a TCP/serial gateway stack alongside application logic, with 4KB SRAM handling packet buffers. SPI and USART interfaces connect radio modules, Ethernet controllers, or RS-485 transceivers, and the ADC digitizes local analog sensors. Operating at 8MHz keeps consumption low for node designs powered by wall adapters or energy harvesting. The self-programming Flash enables over-the-serial firmware updates in the field, a prerequisite for maintainable IoT fleets. Although newer 32-bit MCUs exist, the ATmega128's deterministic single-cycle core, industrial grade, and long availability record make it a dependable choice for simple, robust nodes.
Recommended
Test Equipment and Educational Systems
Bench instruments and university lab platforms frequently use the ATmega128 because the JTAG interface supports full on-chip debugging with Atmel-ICE tools, and the ATmega128 instruction set is a common AVR teaching target. The 10-bit ADC and timers implement data acquisition, PWM signal generation, and frequency measurement directly; the external memory bus supports experiment expansion boards. The 128KB Flash holds monitor firmware plus application code simultaneously, letting students download programs without swapping boot-loaders. Because the -8AI grade tolerates 2.7V to 5.5V, trainers can demonstrate both 3.3V and 5V logic interfacing on one board, a practical benefit in mixed-voltage lab coursework.
Recommended
Recommended Products Summary
Engineering reference data for ATMEGA128L-8AI — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ATMEGA128-16AI | ATMEGA128-16AN | ATMEGA1284-AUR | ATMEGA1284P-MUR | ATMEGA1281V-8AUR |
|---|---|---|---|---|---|---|
| Package | TQFP-64 (14x14 mm) | TQFP-64 - same | TQFP-64 - same | TQFP-64 - same | TQFP-64 - same | TQFP-64 - same |
| Brand | Microchip Technology (Atmel) | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Flash Memory | 128KB | 128KB | 128KB | 128KB | 128KB | 128KB |
| SRAM | 4KB | 4KB | 4KB | 16KB | 16KB | 8KB |
| Max Clock Speed | 8MHz | 16MHz | 16MHz | 20MHz | 20MHz | 8MHz |
| Supply Voltage | 2.7V to 5.5V | 4.5V to 5.5V | 4.5V to 5.5V | 1.8V to 5.5V | 1.8V to 5.5V | 1.8V to 5.5V |
| Operating Temperature | -40C to +85C | -40C to +85C | -40C to +85C | -40C to +85C | -40C to +85C | -40C to +85C |
| Pin Compatibility | Reference (ATmega128 TQFP-64 pinout) | Pin-to-pin identical | Pin-to-pin identical | Largely pin-compatible, peripheral map differs | Largely pin-compatible, peripheral map differs | Similar TQFP-64, verify peripheral map |
Key Differentiators
- Widest supply range in the same ATmega128 pinout (vs ATMEGA128-16AI)
- External memory interface with full address bus (vs ATMEGA1281V-8AUR)
- Industrial temperature at low-voltage grade (vs ATMEGA128L-8AU)
Design Notes
Decouple all three VCC pins (10, 34, 52) and AVCC (pin 24) with 100nF ceramic capacitors placed within 5mm of each pin, plus one bulk 4.7uF to 10uF capacitor per supply rail. AVCC must be connected to VCC even if the ADC is unused, and never exceed the AVCC-VCC delta of 0.3V per the datasheet absolute maximum ratings. If the ADC is used, connect AREF (pin 22) via an RC network (e.g. 10k ohm series resistor and 100nF capacitor) rather than driving it directly from a regulator output.
Route the crystal between XTAL1 (pin 55) and XTAL2 (pin 54) with the shortest possible traces and place load capacitors (typically 12pF to 22pF, per crystal specification) directly at the pins, with a local ground guard ring. Keep the JTAG chain (PF4-PF7) traces short and add header access for production programming. Analog ADC routing on Port F should be separated from fast digital switching on Port A when the external memory bus is active, since bus toggling couples noise into ADC readings.
Three fuse-related issues are the most common ATmega128 field failures: (1) accidentally disabling the JTAGEN fuse locks out on-chip debug while PF4-PF7 revert to ADC pins; (2) enabling the CKOPT fuse is required for crystal operation above 8MHz or in noisy environments; (3) wrong SUT/CKSEL bits can brick boards requiring HV parallel programming via the PEN pin. Also note the ATmega128 supports both 16-bit and 8-bit program counter modes on the external memory interface - misconfiguration of XMCRA causes address bus malfunctions on port C.
Compliance Information
Current Microchip ATmega128 family production parts are offered in RoHS-compliant, lead-free packages; REACH and halogen-free status must be confirmed per lot certificate.