ATMEGA325-16MI - AVR 8-Bit MCU 16MHz 32KB Flash | Microchip
MPN: ATMEGA325-16MI β Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $4.62 | $4.62 |
| 10 | $4.16 | $41.60 |
| 100 | $3.71 | $371.00 |
| 500 | $3.34 | $1,670.00 |
| 1,000 | $3.05 | $3,050.00 |
ATMEGA325-16MI Overview
An 8-bit microcontroller (MCU) is a complete computing system on a single chip, combining a processor core, program memory, data memory, and peripherals such as timers, USARTs, and ADCs. The AVR ATmega family sits within the broader microcontroller hierarchy of embedded processors, positioned for cost-sensitive, general-purpose embedded control where a full 32-bit application processor is unnecessary. Microcontrollers like the ATMEGA325-16MI run bare-metal firmware or an RTOS and directly drive sensors, actuators, displays, and communication links.
Key features include the Advanced RISC architecture with 130 powerful instructions, most executing in a single clock cycle; 16 MIPS throughput at 16MHz; 54 programmable I/O lines; two 8-bit and two 16-bit timers/counters; a 10-bit ADC; USART serial interface; and SPI support. Operating voltage spans 2.7V to 5.5V, and the industrial temperature grade (suffix MI) covers -40C to +85C, suiting harsh environments.
Technically, the AVR core uses a Harvard architecture with separate program and data buses, enabling single-cycle instruction fetch and execution. In-System Programmable (ISP) Flash allows firmware updates on the assembled board via SPI, while boot-section self-programming supports field upgrades. JTAG boundary scan and on-chip debug simplify production test.
Typical applications include industrial automation controllers, consumer appliances, IoT sensor nodes, HVAC and metering systems, and embedded human-machine interfaces where 32KB of code space and 54 GPIO lines cover mid-complexity control tasks.
A key design consideration: at 5V and 16MHz the device runs at its rated maximums, so verify power budget and derating in high-temperature enclosures; the 2.7V to 5.5V range allows battery designs to run at reduced clock speeds for lower consumption.
This page synthesizes distributor pricing, drop-in alternatives, design notes, and application guidance not found in a single manufacturer datasheet, verified as of 2026-09-17.
Drop-in alternatives for ATMEGA325-16MI β same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Quick Comparison Tool β Select alternative parts for side-by-side comparison:
ATMEGA325-16MU
β Drop-Inπ Reference alternative (not in catalog)
ATMEGA325-16MUR
β Drop-In β οΈ εζ°εΎ ιͺθ―β In Stock
$3.28 / Unit
View Datasheet βATMEGA325P-16MI
β Drop-In β οΈ εζ°εΎ ιͺθ―π Reference alternative (not in catalog)
ATMEGA325PA-16MI
β Drop-In β οΈ εζ°εΎ ιͺθ―π Reference alternative (not in catalog)
ATMEGA3250-16MU
β Drop-In β οΈ εζ°εΎ ιͺθ―π Reference alternative (not in catalog)
ATMEGA645-16MU
β Drop-In β οΈ εζ°εΎ ιͺθ―π Reference alternative (not in catalog)
ATMEGA329-16MU
β Drop-In β οΈ εζ°εΎ ιͺθ―π Reference alternative (not in catalog)
ATMEGA325-16MI Maximum Ratings & Electrical Characteristics
| Core Architecture | 8-bit AVR RISC |
| Max Clock Frequency | 16 MHz |
| Program Memory (Flash) | 32 KB (16K x 16) |
| EEPROM | 1 KB |
| SRAM | 2 KB |
| Operating Voltage Range | 2.7 V to 5.5 V |
| Number of I/O | 54 programmable I/O lines |
| Instructions | 130 powerful instructions, most single-cycle |
| Timers/Counters | Two 8-bit and two 16-bit |
| ADC | 10-bit |
| Serial Interfaces | USART, SPI, TWI (I2C-compatible) |
| Package | 64-QFN / MLF (9x9 mm) with exposed pad |
| Mounting Type | Surface Mount |
| Operating Temperature | -40C to +85C (industrial) |
| ISP (In-System Programmable) | Yes |
| JTAG / Debug | JTAG boundary scan and on-chip debug |
| RoHS Status | Compliant (Green per FindIC data) |
ATMEGA325-16MI 64-qfn / mlf (9x9 mm) with exposed pad Pin Configuration Guide
Pin configuration for ATMEGA325-16MI (64-qfn / mlf (9x9 mm) with 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 ATMEGA325-16MI.
Refer to the datasheet for full pin configuration.
Typical Applications
ATMEGA325-16MI is suitable for 6 applications: Industrial Automation Controllers, IoT Sensor Nodes, Consumer Appliance Control, Metering and HVAC Systems, Embedded HMI and Display Panels, Motor and Actuator Drive Boards.
Industrial Automation Controllers
The ATMEGA325-16MI fits industrial control nodes because its -40C to +85C industrial temperature grade and 5V noise immunity match the electrical environment of factory floors. With 54 programmable I/O lines, two 8-bit and two 16-bit timers, and a 10-bit ADC, one MCU can handle relay driving, quadrature encoder reading, and analog sensor acquisition in a single 64-QFN 9x9 mm footprint. The 32KB ISP Flash accommodates state-machine-heavy ladder-style firmware with headroom for boot-section field updates via self-programming. Used as a PLC I/O module or machine sub-controller, it exchanges status with a supervisory PLC over the USART or SPI at several hundred kbps. The exposed-pad QFN on a solid ground plane improves EMI behavior in switch-noise-rich cabinets, and the watchdog timer plus brown-out detection keep firmware deterministic through supply sag events typical of motor-start transients.
Recommended
IoT Sensor Nodes
For battery- or bus-powered IoT sensor nodes, the ATMEGA325-16MI combines a 2.7V to 5.5V supply range with AVR sleep modes, allowing the node to sleep between measurement cycles and wake on timer or pin interrupt. The 10-bit ADC digitizes temperature, humidity, or voltage channels directly, while the USART links to a radio module or RS-485 transceiver for backhaul. The 1KB EEPROM stores calibration constants and node identity through power cycles without external memory. In a 9x9 mm 64-QFN package, the MCU adds minimal board area, and the industrial -40C to +85C rating suits outdoor and rooftop deployments. Designers needing the lowest sleep current should choose the pin-compatible ATMEGA325PA-16MI picoPower variant; the standard 325 remains a solid choice for bus-powered (5V/3.3V) gateways and mains-supplied nodes where sleep current is less critical.
Recommended
Consumer Appliance Control
Appliance control boards - washers, cooktops, air conditioners - require modest compute, many GPIO for buttons/relays, and low unit cost, exactly the profile of the ATMEGA325-16MI. Its 16MHz core executes button scanning, display multiplexing, and relay sequencing with ample margin, while 54 I/O lines frequently eliminate external port expanders, cutting BOM cost. The 32KB Flash holds menu logic, fault logs, and self-test routines; the 1KB EEPROM persists user settings and cycle counters across power interruptions. SPI or USART connects to LED/LCD drivers or a Wi-Fi add-on module in connected-appliance versions. The 2.7V to 5.5V range tolerates loosely regulated appliance supplies after a small LDO stage, and the industrial temperature suffix covers the hot interiors of cooking and laundry products. In-circuit ISP allows final firmware configuration on the production line without desoldering.
Recommended
Metering and HVAC Systems
Utility submeters and HVAC zone controllers benefit from the ATMEGA325-16MI's combination of 10-bit ADC, 2KB SRAM for rolling data buffers, and EEPROM for accumulating energy totals that must survive outages. Timers generate precise gate intervals for pulse-counting energy inputs and PWM outputs for damper or valve actuation. The USART provides standard connectivity to M-Bus/RS-485 metering buses through a transceiver, and TWI (I2C) reads RTC and sensor chips for timestamped records. Operating over -40C to +85C, the part survives rooftop AHU enclosures and unheated meter cabinets. Firmware stored in 32KB ISP Flash leaves room for communication stacks plus tariff logic, while boot-section self-programming enables recalibration updates in the field. The 64-QFN exposed pad, bonded to ground, aids conducted-emission control demanded by metering EMC environments.
Recommended
Embedded HMI and Display Panels
Small human-machine interfaces - keypad-plus-display panels for machines and kiosks - map well onto the ATMEGA325-16MI. A third of the 54 I/O lines directly drive a multiplexed LED segment display or scan a 16-key matrix, while the USART feeds a character LCD or serial OLED module. At 16MHz the core sustains flicker-free multiplexing and debounced touch handling simultaneously. The 2KB SRAM buffers display frame data and menu structures, and 1KB EEPROM stores language selections and setpoints across power-down. The 64-QFN 9x9 mm package fits behind typical panel PCBs, and the industrial temperature rating handles enclosed panels that warm under backlight load. ISP in-circuit programming lets a single board design carry product-specific firmware flashed at end-of-line, simplifying inventory across product variants within the same family of panels.
Recommended
Motor and Actuator Drive Boards
The ATMEGA325-16MI serves as the firmware brain for small brushed-DC and stepper drive boards. Its two 16-bit timers generate phase-correct PWM with resolution high enough for quiet motor control, and two 8-bit timers handle tachometer capture and system ticks. The 10-bit ADC samples current-sense shunts and potentiometer feedback for closed-loop speed or position regulation executed in the single-cycle AVR core at 16MHz - fast enough for kilohertz control loops in C. Direction and enable outputs, plus USART for a host command link, round out a one-chip controller. Brown-out detection and the watchdog protect against stall-induced overcurrent firmware lockups. Placed on a board with a discrete H-bridge driver stage, the 64-QFN MCU keeps logic and power sections spatially separated, and its -40C to +85C grade covers enclosed actuator housings in outdoor equipment.
Recommended
Recommended Products Summary
Engineering reference data for ATMEGA325-16MI β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ATMEGA325-16MU | ATMEGA325P-16MI | ATMEGA325PA-16MI | ATMEGA3250-16MU | ATMEGA645-16MU |
|---|---|---|---|---|---|---|
| Package | 64-QFN / MLF (9x9 mm) | 64-QFN (9x9 mm) - same | 64-QFN (9x9 mm) - same | 64-QFN (9x9 mm) - same | 64-QFN (9x9 mm) - same | 64-QFN (9x9 mm) - same |
| Brand | Microchip Technology (Atmel) | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Max Clock Frequency | 16 MHz | 16 MHz | 16 MHz | 16 MHz | 16 MHz | 16 MHz |
| Flash Memory | 32 KB | 32 KB | 32 KB | 32 KB | 32 KB | 64 KB |
| SRAM | 2 KB | 2 KB | 2 KB | 2 KB | 2 KB | 4 KB |
| Operating Voltage | 2.7 V to 5.5 V | 2.7 V to 5.5 V | 2.7 V to 5.5 V | 1.8 V to 5.5 V | 2.7 V to 5.5 V | 2.7 V to 5.5 V |
| Operating Temperature | -40C to +85C (industrial) | 0C to +70C (commercial) | -40C to +85C (industrial) | -40C to +85C (industrial) | 0C to +70C (commercial) | 0C to +70C (commercial) |
| USART Count | 1 | 1 | 1 | 1 | 2 | 1 |
Key Differentiators
- Industrial temperature grade in the QFN package (vs ATMEGA325-16MU)
- Pin-compatible picoPower upgrade path (vs ATMEGA325PA-16MI)
- Largest Flash option in the same socket (vs ATMEGA645-16MU)
Design Notes
The 64-QFN (9x9 mm) package has a large exposed pad under the die that must be soldered to a grounded copper pour via an array of thermal vias. Skipping the exposed-pad connection is the most common QFN assembly defect: it causes intermittent ground returns and poor thermal performance even when perimeter joints look perfect. Follow Microchip's QFN land-pattern guideline with a solder-mask-defined pad, and use a 4-6 via array (0.3 mm drills) in the pad center. X-ray or acoustic inspection is recommended for the first production run of QFN devices.
Decouple each VCC pin pair with 100 nF ceramic capacitors placed within 3 mm of the pin, plus one bulk 4.7-10 uF capacitor per board. The AVR draws current spikes on clock edges, and QFN packages expose less lead inductance to self-filter, so local decoupling matters more than in DIP designs. At 16MHz/5V operation the device runs at its rated maximum; verify brown-out detector setting (2.7V threshold for 5V systems) is enabled in the fuse configuration so firmware does not execute erratically during supply sag.
Fuse misconfiguration is the top field failure for ATmega parts: setting SPIEN disable, wrong clock source, or RSTDISBL can permanently lock out ISP programming. Always verify fuses with a programmer before release. Also note that PCINT/JTAG pins default to JTAG function on ATmega325 family parts in QFN packages; if those pins are needed as GPIO, clear the JTAGEN fuse or disable JTAG in software via the MCUCSR register twice within four clock cycles per the datasheet.
Compliance Information
FindIC lists ATMEGA325-16MI as GREEN industrial-grade MLF (RoHS-compliant). REACH, halogen-free, and conflict-minerals declarations should be pulled from Microchip's official compliance documents for the exact ordering code.
