ATMEGA128L-8MI - 8-bit AVR MCU, 128KB Flash, 8MHz | Microchip
MPN: ATMEGA128L-8MI ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $7.12 | $7.12 |
| 10 | $6.42 | $64.20 |
| 100 | $5.71 | $571.00 |
| 500 | $5.15 | $2,575.00 |
| 1,000 | $4.68 | $4,680.00 |
ATMEGA128L-8MI Overview
An 8-bit AVR microcontroller is a Harvard-architecture RISC processor that executes most of its 133 instructions in a single clock cycle. Within the embedded-systems hierarchy, it sits as a mid-range microcontroller unit (MCU) within Microchip's AVR ATmega family, combining program memory, data memory, peripherals, and CPU on one die - the classic single-chip embedded controller.
Key features include 128KB self-programming Flash with a boot loader section for field firmware updates, 4KB internal SRAM and 4KB EEPROM for data retention without external memory, and up to 8 MIPS throughput at 8 MHz. The 8-channel 10-bit ADC supports analog sensing, while the JTAG interface enables boundary-scan testing and on-chip debugging. Two 8-bit and two 16-bit timers, USARTs, SPI, and a two-wire interface (I2C) round out the peripheral set.
The advanced RISC architecture pairs 32 general-purpose working registers directly with the ALU, so a single instruction can execute an operation on register contents in one clock cycle. This yields deterministic, fast interrupt response and efficient C-compiler code density - a hallmark of the AVR line. The self-programming Flash allows the device to update its own program memory through a boot-loader routine, eliminating external programming hardware in the field.
Typical applications include industrial automation nodes, building and HVAC controllers, battery-powered instrumentation that leverages the low-power operating modes, and motor-control or sensing boards that use the 10-bit ADC. Its 5V-friendly industrial rating suits noisy factory environments.
Design consideration: the L-suffix device is speed-graded to 8 MHz; driving it above the rated frequency for the supply voltage range violates timing margins. Plan Flash wear-levelling if you store data in the 4KB EEPROM frequently.
This page synthesizes distributor availability data, drop-in alternative options, and practical design notes not found in the manufacturer datasheet.
Drop-in alternatives for ATMEGA128L-8MI — 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-8MI (same form factor and footprint) — differing in Package, Communication Interfaces, Debug Interface, EEPROM, SRAM.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
ATMEGA128L-8MU
✅ Drop-In✓ In Stock
$12.39 / Unit
View Datasheet →ATMEGA128L-8MN
✅ Drop-In✓ In Stock
$7.68 / Unit
View Datasheet →ATMEGA128-16MUR
✅ Drop-In✓ In Stock
$8.4 / Unit
View Datasheet →ATMEGA128-16MUR
✅ Drop-In✓ In Stock
$8.4 / Unit
View Datasheet →ATMEGA128L-8MUR
✅ Drop-In✓ In Stock
$11.75 / Unit
View Datasheet →ATMEGA128L-8MI Maximum Ratings & Electrical Characteristics
| Core Architecture | 8-bit AVR RISC |
| Core Size | 8-bit |
| Maximum Clock Frequency | 8 MHz |
| Flash Program Memory | 128 KB (64K x 16), In-System Programmable |
| SRAM Data Memory | 4 KB |
| EEPROM Data Memory | 4 KB |
| ADC Channels | 8 channels, 10-bit |
| Debug Interface | JTAG (on-chip debug) |
| Instructions | 133 instructions, most single-cycle |
| Throughput | Up to 8 MIPS at 8 MHz |
| Operating Temperature | -40C to +85C (industrial) |
| Package | 64-QFN / MLF, 9x9 mm |
| Mounting Type | Surface Mount |
| Number of Terminals | 64 |
| Series | AVR ATmega |
ATMEGA128L-8MI 64-qfn / mlf, 9x9 mm Pin Configuration Guide
Pin configuration for ATMEGA128L-8MI (64-qfn / mlf, 9x9 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 ATMEGA128L-8MI.
Refer to the datasheet for full pin configuration.
Typical Applications
ATMEGA128L-8MI is suitable for 6 applications: Industrial Automation Nodes, Battery-Powered Instrumentation, Building and HVAC Controllers, Motor Control Subsystems, Sensor Hubs and Data Acquisition, Legacy AVR System Maintenance.
Industrial Automation Nodes
The ATMEGA128L-8MI fits industrial control nodes because its industrial temperature rating, dual USARTs for Modbus RTU, and 8-channel 10-bit ADC cover sensor acquisition and fieldbus communication in one chip. A typical node connects 4-20 mA or 0-10 V sensor channels to PF0-PF7 through RC filtering, uses USART1 at 9600-115200 baud for RS-485 Modbus, and drives relays or actuators with timer PWM outputs. Running at 8 MHz keeps dynamic power low and EMI modest in electrically noisy cabinets. The 128KB Flash leaves generous headroom for protocol stacks, and the JTAG port supports on-chip debugging of state machines without instrumented firmware builds.
Recommended
Battery-Powered Instrumentation
In portable and battery-powered measurement instruments, the ATMEGA128L-8MI's 8 MHz speed grade is an advantage rather than a limitation: lower clock frequency directly reduces switching losses in the CMOS core, and the AVR power management unit supports idle, power-down, and power-save sleep modes entered between samples. A representative design wakes the MCU on a timer interrupt, performs a 10-bit ADC conversion on one of eight channels, stores results in the 4KB EEPROM or streams them over USART, then returns to power-down. The 128KB Flash accommodates logging firmware with display and menu code, while the 4KB SRAM buffers sample records between radio or serial transmissions.
Recommended
Building and HVAC Controllers
HVAC zone controllers benefit from the ATMEGA128L-8MI's blend of analog inputs, timers, and communication ports. The 8-channel 10-bit ADC reads temperature sensors (NTC thermistors via divider networks), humidity and pressure transmitters, while 16-bit timers generate phase-correct PWM for damper actuators and variable-speed fan control. A USART links to RS-485 building networks (BACnet MS/TP-style buses or Modbus), and the two-wire interface addresses I2C RTC and EEPROM chips for schedule storage. The industrial temperature rating tolerates rooftop and mechanical-room environments, and the self-programming Flash allows field firmware updates of control schedules without replacing hardware.
Recommended
Motor Control Subsystems
The ATMEGA128L-8MI serves as the supervisory and PWM controller in small motor drive subsystems. Its two 16-bit timers with output-compare channels generate complementary or independent PWM streams for DC motor and small BLDC control, while the 10-bit ADC samples current-shunt voltages and potentiometer speed references on up to eight channels. At 8 MHz, the single-cycle ALU executes current-loop bookkeeping fast enough for low-cost drives without a dedicated DSP. The JTAG interface enables cycle-accurate debugging of commutation routines, and the 4KB EEPROM retains calibration tables (gain, offset, limits) across power cycles - a frequent requirement in appliance and pump controls.
Recommended
Sensor Hubs and Data Acquisition
As a sensor hub, the ATMEGA128L-8MI aggregates digital and analog sensors onto a single upstream link. The two-wire interface and SPI ports connect to environmental and motion sensors, the 8-channel 10-bit ADC digitizes analog transducers, and one USART forwards framed packets to a gateway over RS-232/RS-485 while the second remains available for local service access. The 4KB SRAM supports ring buffers for burst acquisition, and the 128KB Flash hosts protocol and filtering code with room to spare. The industrial temperature grade allows deployment in unconditioned enclosures, and the MLF package's exposed paddle improves heat spreading when the board is fully sealed.
Recommended
Legacy AVR System Maintenance
A significant ongoing use of the ATMEGA128L-8MI is sustaining existing ATmega128-based products - medical bench instruments, laboratory equipment, and industrial controllers designed in the 2000s whose firmware is written against the ATmega128 register map. Because the -8MI is the same silicon in the same 64-QFN footprint, repair and low-volume production of these systems needs no redesign or code changes. The JTAG interface remains invaluable for diagnosing field-returned units, and the in-system programmable Flash allows reflashing service firmware. Sourcing from authorized channels such as XAIPART mitigates counterfeit risk that plagues mature AVR parts on the gray market.
Recommended
Recommended Products Summary
Engineering reference data for ATMEGA128L-8MI — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ATMEGA128L-8MU | ATMEGA128L-8MN | ATMEGA128-16MU | ATMEGA128-16MUR |
|---|---|---|---|---|---|
| Package | 64-QFN (MLF, 9x9 mm) | 64-QFN (MLF, 9x9 mm) - same | 64-QFN (MLF, 9x9 mm) - same | 64-QFN (MLF, 9x9 mm) - same | 64-QFN (MLF, 9x9 mm) - same |
| Brand | Microchip Technology (Atmel) | Microchip Technology (Atmel) | Microchip Technology (Atmel) | Microchip Technology (Atmel) | Microchip Technology (Atmel) |
| Flash Memory | 128 KB | 128 KB | 128 KB | 128 KB | 128 KB |
| SRAM / EEPROM | 4 KB / 4 KB | 4 KB / 4 KB | 4 KB / 4 KB | 4 KB / 4 KB | 4 KB / 4 KB |
| Max Clock Frequency | 8 MHz | 8 MHz | 8 MHz | 16 MHz | 16 MHz |
| Temperature Grade | Industrial (-40C to +85C) | Industrial | Verify suffix per ordering code | Industrial | Industrial |
| ADC | 8-channel, 10-bit | 8-channel, 10-bit | 8-channel, 10-bit | 8-channel, 10-bit | 8-channel, 10-bit |
| JTAG On-Chip Debug | Yes | Yes | Yes | Yes | Yes |
Key Differentiators
- Maximum Flash in classic ATmega family (vs ATMEGA1281V-8MU)
- Lower power than the 16 MHz grade (vs ATMEGA128-16MU)
- JTAG on-chip debugging retained (vs ATMEGA328PB-MU)
Design Notes
Respect the 8 MHz speed grade of the ATMEGA128L-8MI. Clocking the L-grade part above 8 MHz - for example by reusing a 16 MHz crystal from an ATMEGA128-16 design - violates the device timing specification and produces intermittent failures that worsen with temperature. If a legacy board was designed for the 16 MHz grade, either fit a 16 MHz-qualified part (ATMEGA128-16MU, same package) or swap the crystal. Also verify CKOPT and clock-source fuses when porting code between speed grades.
The MLF/QFN package requires via-in-pad or perimeter fanout under the exposed center paddle for reliable solder joints and ground return. Place at least a 9x9 via array (0.3 mm vias) connected to the ground plane beneath the paddle, and keep the VCC/AVCC/GND decoupling network (100 nF per supply pin plus 10 uF bulk) within 3 mm of the package edge. AVCC must be tied to VCC through an LC filter when ADC accuracy matters, per the ATmega128 datasheet ADC supply recommendations.
Estimated: for an ATMEGA128L-8MI running actively at 8 MHz in the 5 V range, dynamic current is on the order of a few milliamps to roughly 10 mA class (consult the datasheet active-supply-current curves for your exact voltage and clock), dropping to microamp levels in power-down mode with WDT off. Budget the regulator for the active figure plus I/O pin loads, and design sleep-entry firmware early - leaving the ADC or timers enabled in idle mode erodes most of the battery benefit in instrumentation applications.
Do not reclaim the JTAG pins (PC2-PC5: TCK, TMS, TDO, TDI) as GPIO without updating the JTAG-enable fuse - by default these pins are dedicated to JTAG after reset, and code that expects them as I/O will appear to fail. Conversely, disable JTAG via fuse when all port C bits are needed, accepting loss of on-chip debug. For EEPROM-heavy logging, implement wear management: the 4KB EEPROM has finite endurnace and unmanaged writes in a loop can exhaust blocks within months in continuously powered systems.
Compliance Information
Listed by DigiKey and Mouser as a standard RoHS-compliant Microchip production part. REACH, halogen-free, and conflict-minerals declarations not stated in the provided data - request certificates of conformance from Microchip.
