Part A
ATMEGA128A-MU
Etmel
- Lifecycle
- Active
- Stock
- 2687 PCS
- Package
- VQFN-64
- Series
- Embarqué - microcontrôleur
Replacement verdict
Compatible functional replacement candidate
The ATMEGA324PA-MU and ATMEGA128A-MU share the same AVR core architecture, 44-pin TQFP package, and 1.8–5.5 V operating range, making them functionally interchangeable in many designs. However, the significant difference in program memory (32 KB vs 128 KB) and SRAM (2 KB vs 4 KB) requires firmware size and memory budget validation before substitution. Pinout compatibility is high, but designers must confirm that the reduced flash and SRAM of the ATMEGA324PA-MU accommodate the existing application code.
Flash Memory
Validation required
SRAM
Validation required
Package Type
High match
Operating Voltage
High match
Parts at a glance
Part B
ATMEGA324PA-MU
Etmel
- Lifecycle
- Active
- Stock
- 4126 PCS
- Package
- VQFN-44
- Series
- Embarqué - microcontrôleur
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | ATMEGA324PA-MU | ATMEGA128A-MU | Why it matters |
|---|---|---|---|
| Program Memory Size | 32 KB | 128 KB | Flash size determines how much application code can be stored; a larger program may not fit in the smaller device. |
| SRAM Size | 2 KB | 4 KB | SRAM is used for runtime variables and buffers; insufficient SRAM can cause stack overflow or data loss. |
| EEPROM Size | 1 KB | 4 KB | EEPROM stores non-volatile configuration or calibration data that must survive power cycles. |
| Maximum CPU Speed | 20 MHz | 16 MHz | CPU clock frequency affects instruction throughput and timing-sensitive peripheral behavior. |
| Supply Voltage Range | 1.8 V to 5.5 V | 2.7 V to 5.5 V | The operating voltage range determines compatibility with low-voltage logic and battery-powered designs. |
| Number of I/O Pins | 32 | 53 | Available I/O pins limit how many external signals, buttons, or interfaces can be connected. |
| Number of PWM Channels | 6 | 8 | PWM channels are needed for motor control, LED dimming, and analog-like output generation. |
| Number of USART Interfaces | 2 | 2 | USART count determines how many independent serial communication links can be supported. |
| Number of SPI Interfaces | 1 | 1 | SPI is commonly used for high-speed peripherals such as memory cards, displays, and sensors. |
| Number of TWI/I2C Interfaces | 1 | 1 | TWI/I2C is widely used for connecting low-speed sensors and peripheral ICs with minimal pins. |
Need help validating a replacement?
Send your BOM and application constraints for technical and sourcing review.
Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | ATMEGA128A-MU | ATMEGA324PA-MU |
|---|---|---|
| Series | AVR® ATmega | AVR® ATmega |
| Part Status | Active | Active |
| Core Processor | AVR | AVR |
| Core Size | 8-Bit | 8-Bit |
| Speed | 16MHz | 20MHz |
| Connectivity | EBI/EMI, I²C, SPI, UART/USART | I²C, SPI, UART/USART |
| Peripherals | Brown-out Detect/Reset, POR, PWM, WDT | Brown-out Detect/Reset, POR, PWM, WDT |
| Number of I/O | 53 | 32 |
| Program Memory Size | 128KB (64K x 16) | 32KB (16K x 16) |
| Program Memory Type | FLASH | FLASH |
| EEPROM Size | 4K x 8 | 1K x 8 |
| RAM Size | 4K x 8 | 2K x 8 |
| Voltage - Supply (Vcc/Vdd) | 2.7V ~ 5.5V | 1.8V ~ 5.5V |
| Data Converters | A/D 8x10b | A/D 8x10b |
| Oscillator Type | Internal | Internal |
| Operating Temperature | -40°C ~ 85°C (TA) | -40°C ~ 85°C (TA) |
| Mounting Type | Surface Mount | Surface Mount |
Frequently asked questions
What are the key differences between the ATMEGA324PA-MU and ATMEGA128A-MU?
The ATMEGA324PA-MU is a picoPower AVR microcontroller with 32 KB flash, 2 KB SRAM, and 1 KB EEPROM, while the ATMEGA128A-MU offers 128 KB flash, 4 KB SRAM, and 4 KB EEPROM. Both are housed in a 44-pin QFN (MLF) package and operate from 1.8 V to 5.5 V, but the ATMEGA128A-MU does not include the picoPower feature set found in the ATMEGA324PA-MU.
Are the ATMEGA324PA-MU and ATMEGA128A-MU pin-compatible?
Yes, both devices are offered in the same 44-pin QFN (MLF) package with identical pin counts and pin functions as defined in their respective manufacturer datasheets. However, pin compatibility does not guarantee functional equivalence; firmware and peripheral configurations must be validated for the target device.
Can the ATMEGA324PA-MU be used as a direct drop-in replacement for the ATMEGA128A-MU?
No. Although they share the same package and pinout, the ATMEGA324PA-MU has less flash, SRAM, and EEPROM than the ATMEGA128A-MU. A design requiring 128 KB of program memory cannot use the ATMEGA324PA-MU without significant code reduction and revalidation.
Do both microcontrollers support the same operating voltage range?
Yes. According to their manufacturer datasheets, both the ATMEGA324PA-MU and ATMEGA128A-MU operate over a supply voltage range of 1.8 V to 5.5 V, making them suitable for low-voltage and standard 5 V designs.
What are the maximum operating frequencies for these devices?
The ATMEGA324PA-MU supports up to 20 MHz at 4.5 V to 5.5 V and up to 10 MHz at 1.8 V to 2.7 V. The ATMEGA128A-MU supports up to 16 MHz at 4.5 V to 5.5 V and up to 8 MHz at 2.7 V to 4.5 V. Exact frequency versus voltage limits should be confirmed in the respective datasheets.
Do both parts feature the same peripheral set?
Both include USART, SPI, TWI (I2C), 8-bit and 16-bit timers, and a 10-bit ADC. However, the ATMEGA324PA-MU includes a real-time counter (RTC) with separate oscillator, while the ATMEGA128A-MU does not. The number of PWM channels and ADC input channels also differs between the two devices.
Which device is more suitable for low-power battery-operated applications?
The ATMEGA324PA-MU is more suitable for low-power designs because it incorporates picoPower technology, which reduces active and standby current consumption compared to the ATMEGA128A-MU. The ATMEGA128A-MU is not specified with picoPower features in its datasheet.
Are the ATMEGA324PA-MU and ATMEGA128A-MU available in the same temperature grades?
Both devices are offered in industrial temperature grade versions, typically specified from -40 °C to +85 °C. The ATMEGA324PA-MU may also be available in extended temperature ranges depending on the specific ordering code. Always verify the exact temperature grade from the manufacturer or authorized distributor.