ATMEGA128L-8MJ - 8-bit AVR MCU, 128KB Flash, 8MHz | Microchip
MPN: ATMEGA128L-8MJ ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $15.01 | $15.01 |
| 10 | $14.12 | $141.20 |
| 100 | $12.95 | $1,295.00 |
| 500 | $11.8 | $5,900.00 |
| 1,000 | $10.95 | $10,950.00 |
ATMEGA128L-8MJ Overview
An 8-bit AVR microcontroller is a Harvard-architecture RISC processor that executes most instructions in a single clock cycle. Within the power-management hierarchy, the ATmega128 family sits in the general-purpose mid-range segment: microcontroller -> embedded processor -> system-on-chip building block. The AVR core uses 32 general-purpose working registers directly connected to the ALU, allowing one-cycle execution that delivers approximately 8 MIPS at the 8 MHz maximum clock of this L-grade (low-voltage) variant.
Key features include 133 powerful instructions, 53 general-purpose I/O lines, four flexible Timer/Counters with compare modes and PWM, a Real Time Counter, and in-system programmable Flash with Read-While-Write capability for field firmware updates.
Communication and analog capability are comprehensive for its class: two USARTs, a byte-oriented Two-wire Serial Interface (TWI/I2C-compatible), an SPI serial port, an 8-channel 10-bit ADC, and a JTAG interface for on-chip debugging and boundary-scan. This peripheral set lets a single ATMEGA128L-8MJ replace a MCU plus separate UART, ADC, and EEPROM devices in cost-sensitive boards.
Typical applications include industrial control panels, building automation nodes, battery-powered instrumentation benefiting from the low-voltage L variant, and legacy designs originally built around the pin-compatible ATmega103, which the ATmega128 can directly replace.
Design consideration: keep the ADC reference clean and decouple AVCC, and note that at 8 MHz the device is specified across the full 2.7V-5.5V range, while 16 MHz operation would require the 16 MHz grade and 4.5V-5.5V supply.
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes not found in the manufacturer datasheet.
Drop-in alternatives for ATMEGA128L-8MJ — 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-8MJ (same form factor and footprint) — differing in Package, SRAM, RoHS Status, Timers/Counters, Core Architecture.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
ATMEGA128L-8MU
✅ Drop-In✓ In Stock
$12.39 / Unit
View Datasheet →ATMEGA128-16MJ
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$4.48 / Unit
View Datasheet →ATMEGA128-16MUR
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$8.4 / Unit
View Datasheet →ATMEGA1281V-8MU
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$5.92 / Unit
View Datasheet →ATMEGA128L-8MJ Maximum Ratings & Electrical Characteristics
| Core Architecture | 8-bit AVR RISC |
| Flash Program Memory | 128 KB (In-System Programmable, Read-While-Write) |
| SRAM | 4 KB |
| EEPROM | 4 KB |
| Maximum Clock Frequency | 8 MHz |
| Operating Voltage Range | 2.7 V to 5.5 V |
| General Purpose I/O Lines | 53 |
| Working Registers | 32 x 8-bit |
| Timers/Counters | 4 (with compare modes and PWM) |
| Real Time Counter | Yes (RTC) |
| USART | 2 |
| Two-wire Serial Interface (TWI) | Yes (byte-oriented) |
| ADC | 8-channel, 10-bit |
| JTAG | Yes (on-chip debug and boundary scan) |
| Package | 64-VFQFN with Exposed Pad (MLF) |
| Mounting Type | Surface Mount |
| Throughput | Approx. 8 MIPS at 8 MHz (most instructions single-cycle) |
ATMEGA128L-8MJ 64-vfqfn with exposed pad (mlf) Pin Configuration Guide
Pin configuration for ATMEGA128L-8MJ (64-vfqfn with exposed pad (mlf) 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-8MJ.
Refer to the datasheet for full pin configuration.
Typical Applications
ATMEGA128L-8MJ is suitable for 6 applications: Industrial Control Panels, Battery-Powered Instrumentation, Legacy ATmega103 Design Migration, Building Automation Nodes, Embedded Data Loggers, Motor Control and PWM Actuation.
Industrial Control Panels
The ATMEGA128L-8MJ fits industrial control panels because 128KB of ISP Flash accommodates large state-machine and HMI firmware, 53 GPIO lines drive relays, indicators, and keypads without expansion ICs, and two USARTs link to Modbus RTU field buses plus a local service port. The 2.7V-5.5V supply tolerance rides out noisy 5V rails, while the 10-bit ADC with eight channels reads potentiometers, sensors, and current-shunt circuits directly. The four timers with PWM outputs handle heater dimming and motor speed control, and the RTC supports time-stamped event logging to the 4KB EEPROM. Its industrial operating grade and JTAG debug support make commissioning and field diagnostics straightforward in panel environments.
Recommended
Battery-Powered Instrumentation
The 'L' low-voltage grade makes the ATMEGA128L-8MJ a strong fit for battery-powered instruments: it is specified from 2.7V to 5.5V, so a two-cell lithium or single-cell with boost converter supplies the part with margin through the discharge curve, and the full 8 MHz clock remains available at 3.3V. The AVR sleep modes combined with the asynchronous RTC allow microamp-class standby between measurement cycles, while the 4KB EEPROM retains calibration constants without battery backup. The integrated 8-channel 10-bit ADC samples sensor bridges directly, avoiding a separate converter. 53 GPIO and TWI allow display and external FRAM expansion, letting one MCU span measurement, logging, and user-interface functions.
Recommended
Legacy ATmega103 Design Migration
According to the Microchip datasheet, the ATmega128 is 100% pin compatible with ATmega103 and can replace it on existing printed circuit boards, with application note 'Replacing ATmega103 by ATmega128' detailing migration considerations. The ATMEGA128L-8MJ therefore serves maintenance engineers keeping ATmega103-era boards alive: the 64-QFN footprint drops onto the existing land pattern, the 128KB Flash doubles the code space of ATmega103, and the enhanced TWI and JTAG debug arrive for free. MIG2-compatible fuse settings and the M103 fuse mode ease transition of legacy firmware. For obsolete-controller obsolescence events, this is the lowest-risk, zero-PCB-rework migration path documented by the manufacturer.
Recommended
Building Automation Nodes
In building automation, the ATMEGA128L-8MJ integrates sensing, actuation, and network communication in one device. Its byte-oriented TWI connects environmental sensors and RTC modules on a two-wire bus, two USARTs backhaul to RS-485 network converters, and SPI interfaces flash logging memory. The 10-bit ADC with eight channels samples temperature, humidity, and occupancy inputs, while four PWM timers drive damper motors and dimmable LED lighting channels. The 2.7V-5.5V operating range allows a shared 3.3V rail with modern sensors. With 128KB Flash, full BACnet-lite or proprietary protocol stacks fit comfortably, and the JTAG interface supports production boundary-scan testing of assembled nodes.
Recommended
Embedded Data Loggers
The ATMEGA128L-8MJ suits embedded data-logger designs that must run unattended for months. The RTC provides accurate timestamping, the 4KB EEPROM survives power loss for rolling configuration and index storage, and SPI-connected SD or serial-flash media receives logged records through the hardware SPI port at low CPU overhead. Two USARTs allow one channel for GPS or modem modules and a second for local diagnostics. Sleep-mode current plus the low-voltage 2.7V-5.5V grade support primary-cell power budgets, and the ADC's internal reference options simplify sensor front ends. 128KB Flash holds protocol, compression, and file-system firmware with ample headroom for field firmware updates via Read-While-Write bootloading.
Recommended
Motor Control and PWM Actuation
With four Timer/Counters offering compare modes and PWM, the ATMEGA128L-8MJ generates multiple independent PWM channels for DC motor, stepper, and actuator control. The 8 MHz core executes PID control loops in microseconds per iteration, leaving CPU margin for command parsing over USART. Ten-bit ADC inputs read back current shunts and position potentiometers, enabling closed-loop control without external converters. Operating to 5.5V simplifies gate-drive level compatibility with 5V logic MOSFET drivers, while the 64-QFN exposed pad provides a low-inductance ground for switching-noise immunity. Designers should keep analog traces away from PWM outputs and use the ADC noise-reduction sleep mode for sensitive sampling.
Recommended
Recommended Products Summary
Engineering reference data for ATMEGA128L-8MJ — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ATMEGA128L-8MU | ATMEGA128-16MJ | ATMEGA128-16MU | ATMEGA1281V-8MU |
|---|---|---|---|---|---|
| Package | 64-VFQFN (Exposed Pad) | 64-VFQFN (Exposed Pad) - same | 64-VFQFN (Exposed Pad) - same | 64-VFQFN (Exposed Pad) - same | 64-MLF/QFN - same footprint |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Flash | 128 KB | 128 KB | 128 KB | 128 KB | 128 KB |
| SRAM | 4 KB | 4 KB | 4 KB | 4 KB | 8 KB |
| Max Clock | 8 MHz | 8 MHz | 16 MHz | 16 MHz | 8 MHz |
| Supply Voltage | 2.7 V - 5.5 V | 2.7 V - 5.5 V | 4.5 V - 5.5 V | 4.5 V - 5.5 V | 2.7 V - 5.5 V |
| EEPROM | 4 KB | 4 KB | 4 KB | 4 KB | 4 KB |
Key Differentiators
- Full low-voltage range with no clock penalty (vs ATMEGA128-16MJ)
- Direct ATmega103 PCB replacement (vs ATMEGA1281V-8MU)
- Doubled SRAM headroom for new designs (vs ATMEGA128L-8MU)
Design Notes
Decouple every VCC/AVCC pin pair of the 64-QFN with 100 nF ceramic capacitors placed within 2 mm of the pins, plus one 10 uF bulk capacitor near the package. Connect the exposed pad to a solid ground plane with an array of vias - it is the primary thermal and ground return path. At 8 MHz and 5V, active current is in the tens of milliamps per the ATmega128 datasheet, so trace sizing is easy, but brown-out detection should be enabled via fuse for battery and industrial supplies.
Route the JTAG (TCK/TMS/TDO/TDI) header on all new boards even if unused - it provides production boundary-scan test and on-chip debug with MPLAB SNAP-class tools, and disabling JTAG later is a fuse setting. Keep the ADC front end (AREF, AVCC, sensing traces) physically separated from PWM and USART switching traces; use the ADC noise canceller sleep mode during sampling for best effective-bit performance.
Two frequent migration errors: first, the ATmega128 needs the M103 compatibility fuse explicitly disabled to access its full feature set (TWI, enhanced USART, extra SRAM mapping) when replacing an ATmega103 - leaving it set masks peripherals. Second, the L (8 MHz) and 16 MHz grades differ in supply range: an 8MJ run at 16 MHz or below 2.7V violates the datasheet operating envelope. Verify fuse bits and speed/voltage pairing before release.
Compliance Information
Compliance status for the ATMEGA128L-8MJ ordering code is not stated in the retrieved distributor data; request certificate of conformance from Microchip or your supplier.
