ATMEGA325-16AU - 32KB Flash 16MHz AVR 8-Bit MCU | Microchip
MPN: ATMEGA325-16AU β Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $3.35 | $3.35 |
| 10 | $3.05 | $30.50 |
| 100 | $2.85 | $285.00 |
| 500 | $2.6 | $1,300.00 |
| 1,000 | $2.4 | $2,400.00 |
ATMEGA325-16AU Overview
A microcontroller unit (MCU) is a single integrated circuit that combines a processor core, program memory, data memory, and peripherals into one chip, sitting at the top of the embedded-electronics hierarchy (MCU -> embedded processor -> integrated circuit -> semiconductor). The AVR architecture at the heart of this device is a modified Harvard 8-bit RISC design in which most of the 131 instructions execute in a single clock cycle, delivering up to 16 MIPS throughput at 16MHz.
Key features of the ATMEGA325-16AU include 32KB of self-programmable FLASH with 10,000 write-cycle endurance, 1KB of EEPROM for data retention, 2KB of internal SRAM, a 10-bit ADC, UART, SPI, and a watchdog timer. The part operates from a 4.5V to 5.5V supply per the digchip specification listing (the ATmega325 family datasheet documents a 2.7V to 5.5V range for the V variant), with an operating temperature range of -40C to +85C for the industrial grade AU suffix.
Architecturally, the device pairs the AVR core with separate program and data buses, fast-register-file access, and single-cycle ALU operations, which is why AVR MCUs achieve high code density and deterministic real-time behavior compared with older CISC 8-bit designs.
Typical applications include industrial control panels with LCD interfaces, building automation and HVAC controllers, metering equipment, and hobby/prototyping boards supported by the MegaCore Arduino hardware package.
When designing with this MCU, remember that the 16MHz -16 speed grade requires a 4.5V to 5.5V supply; lower-voltage designs must use the V variant and derate clock speed accordingly.
This page adds value beyond the datasheet by consolidating distributor pricing, verified drop-in alternatives, design notes, and an engineering-focused FAQ in one AI-citable reference.
Drop-in alternatives for ATMEGA325-16AU β 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 ATMEGA325-16AU (same form factor and footprint) β differing in Package, Operating Temperature, Maximum Clock Frequency, Instruction Set, Program Memory Type.
Quick Comparison Tool β Select alternative parts for side-by-side comparison:
ATMEGA325P-16AU
β Drop-In β οΈ εζ°εΎ ιͺθ―π Reference alternative (not in catalog)
ATMEGA325V-8AU
β Drop-In β οΈ εζ°εΎ ιͺθ―π Reference alternative (not in catalog)
ATMEGA3250-16AU
β Drop-Inβ In Stock
$5.74 / Unit
View Datasheet βATMEGA3250P-20AU
β Drop-Inβ In Stock
$1.8 / Unit
View Datasheet βATMEGA645-16AU
β Drop-Inπ Reference alternative (not in catalog)
ATMEGA325-16AU Maximum Ratings & Electrical Characteristics
| Core Architecture | 8-bit AVR RISC |
| Program Memory Size | 32KB (16K x 16) FLASH |
| EEPROM Size | 1KB |
| SRAM Size | 2KB |
| Maximum Clock Frequency | 16 MHz |
| Supply Voltage Range | 4.5 V to 5.5 V |
| Number of I/O Pins | 54 |
| Package | 64-TQFP (14 x 14 mm, 0.8 mm pitch) |
| Mounting Type | Surface Mount |
| Operating Temperature | -40C to +85C |
| Instruction Set | 131 instructions, mostly single-cycle |
| Peripherals | 10-bit ADC, UART, SPI, Watchdog Timer, Timers |
| In-System Programming | Yes (ISP FLASH) |
| Life Cycle Stage | ACTIVE |
ATMEGA325-16AU 64-tqfp (14 x 14 mm, 0.8 mm pitch) Pin Configuration Guide
Pin configuration for ATMEGA325-16AU (64-tqfp (14 x 14 mm, 0.8 mm pitch) 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 ATMEGA325-16AU.
Refer to the datasheet for full pin configuration.
Typical Applications
ATMEGA325-16AU is suitable for 6 applications: Industrial Control Panels, Metering and Measurement Equipment, Building Automation and HVAC Controllers, Consumer Appliance Control, Hobby, Prototyping and Education, Test Fixtures and Production Jigs.
Industrial Control Panels
The ATMEGA325-16AU fits industrial control panels because its 54 general-purpose I/O lines, 32KB FLASH, and 16MHz single-cycle AVR core provide enough concurrent keypad scanning, relay driving, and status indication in one chip. The industrial -40C to +85C temperature grade of the AU suffix matches factory-floor ambient conditions, and the 4.5V to 5.5V supply aligns with legacy 5V industrial logic levels, simplifying level compatibility with optocouplers and relays. In a typical panel design the MCU reads switches through the 10-bit ADC or digital ports, drives a segment LCD or LED indicators, and communicates upstream over the UART or SPI. Because most of the 131 AVR instructions execute in one clock cycle, loop response is deterministic, which helps with timeout and sequencing logic in machine control.
Recommended
Metering and Measurement Equipment
Utility meters and measurement instruments benefit from the ATMEGA325-16AU combination of a 10-bit ADC for analog sensing, 1KB EEPROM for nonvolatile calibration and consumption records, and 2KB SRAM for accumulation buffers. The EEPROM's endurance supports periodic calibration writes without dedicated external memory, and the 32KB ISP FLASH accommodates firmware that includes communication protocols plus measurement math. The 5V operating range gives a wider ADC input span for shunt- or divider-based sensing than 3.3V-only MCUs, improving effective resolution on small signals. Firmware can be updated in the field through the In-System Programming interface, which is valuable for tariff or calibration updates on installed meters. The 64-TQFP package provides enough pins for LCD segments, pulse outputs, and a serial port simultaneously.
Recommended
Building Automation and HVAC Controllers
HVAC zone controllers and building automation nodes use the ATMEGA325-16AU's UART and SPI for RS-485 gateway bridging and sensor bus communication, while the 54 I/O pins directly drive dampers, triac triggers, and fan relays. The 16MHz core leaves ample timing margin for PID loops sampled at 10-100Hz, and the watchdog timer adds the autonomous recovery that building systems require for unattended operation. The -40C to +85C range covers rooftop and mechanical-room environments. The 1KB EEPROM stores setpoints, schedules, and runtime-hour counters that must survive power outages. Because the ATmega325 family shares the AVR toolchain used across many other Microchip MCUs, integrators can reuse code and programming infrastructure across a building's mixed controller fleet, reducing maintenance cost over a 10-20 year system life.
Recommended
Consumer Appliance Control
White-goods and small-appliance controllers adopt the ATMEGA325-16AU for its single-chip integration of display driving, keypad input, and actuator control. The 32KB FLASH is sufficient for menu-driven user interfaces, safety interlock logic, and motor timing routines, while the 5V supply simplifies interfacing with the discrete power stage and zero-cross detection circuits common in appliance designs. The 64-pin TQFP (14x14 mm) footprint offers enough LCD segment or LED matrix drive lines for an integrated user interface without a dedicated display controller. Deterministic single-cycle instruction execution makes tick-timer based motor and heater control straightforward. Long-term availability matters in appliance manufacturing, and the part's active lifecycle status plus multi-distributor stock (13 distributors per Octopart as of 2026-09-17) supports extended production commitments.
Recommended
Hobby, Prototyping and Education
The ATMEGA325-16AU is supported by the MCUdude MegaCore Arduino hardware package, which explicitly lists ATmega325 among supported devices, giving hobbyists and educators the Arduino IDE, libraries, and bootloader ecosystem on a 64-pin, 54-I/O device. This makes it a natural step-up part from the ATmega328 for students who need more ports for LED matrices, keypads, and parallel peripherals. The wide availability of DIP-adapters for TQFP-64 and low single-unit pricing (about $2.25 to $3.35 as of 2026-09-17) lowers the barrier to classroom use. In-System Programming via a low-cost ISP programmer lets beginners flash firmware repeatedly, and the 10,000-cycle FLASH endurance tolerates years of iterative labs. The 5V operating range also makes the chip breadboard-friendly with legacy 5V peripherals and sensors.
Recommended
Test Fixtures and Production Jigs
In-circuit test fixtures and production programming jigs use the ATMEGA325-16AU because its abundant I/O can concurrently interface with bed-of-nails channels, status lamps, pass/fail indicators, and a UART link to the factory MES system. The 16MHz core executes fixture sequencing scripts fast enough for high-throughput lines, and the ISP capability lets the same fixture program target boards before testing them. The industrial temperature range tolerates non-conditioned shop-floor environments, and 2KB SRAM buffers test logs between uploads. Because spare availability spans DigiKey, Mouser, LCSC, and 13 total distributors (per Octopart, 2026-09-17), jig builders can source replacement controllers quickly to minimize line downtime. The 64-TQFP socketed on adapter boards also simplifies quick swaps during fixture maintenance.
Recommended
Recommended Products Summary
Engineering reference data for ATMEGA325-16AU β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ATMEGA325P-16AU | ATMEGA3250-16AU | ATMEGA645-16AU | ATMEGA325V-8AU |
|---|---|---|---|---|---|
| Package | 64-TQFP (14x14 mm) | 64-TQFP - same | 64-TQFP - same | 64-TQFP - same | 64-TQFP - same |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Program Memory (FLASH) | 32KB | 32KB | 32KB | 64KB | 32KB |
| SRAM | 2KB | 2KB | 2KB | 4KB | 2KB |
| Max Clock Speed | 16 MHz | 16 MHz | 16 MHz | 16 MHz | 8 MHz |
| Supply Voltage | 4.5 V to 5.5 V | 4.5 V to 5.5 V | 4.5 V to 5.5 V | 4.5 V to 5.5 V | 2.7 V to 5.5 V |
| I/O / Port Configuration | 54 I/O | 54 I/O | More I/O (extra ports for LCD drive) | 54 I/O class | 54 I/O |
| Power Feature | Standard AVR power profile | picoPower (lower sleep current) | Standard | Standard | Low-voltage optimized |
Key Differentiators
- 5V-native 16MHz operation (vs ATMEGA325V-8AU)
- Lower power drop-in available (vs ATMEGA325P-16AU)
- Memory-upgrade path without redesign (vs ATMEGA645-16AU)
Design Notes
The -16 speed grade requires a 4.5V to 5.5V supply; running 16MHz below 4.5V is out of specification and can cause marginal timing failures that appear only at temperature extremes. If your system rail is 3.3V, select the ATMEGA325V-8AU instead and accept the 8MHz ceiling. Decouple each VCC/GND pin pair with 100nF ceramics placed within a few millimeters of the pins, plus one bulk 10uF per supply domain. Estimated: total board current for the MCU alone at 16MHz/5V is typically in the low-tens of mA per AVR family datasheet behavior - budget accordingly in 5V rail sizing.
For the 64-TQFP (0.8 mm pitch), use a standard QFP-64 land pattern with ~0.45-0.5 mm pads; the exposed lead tips permit straightforward reflow or drag soldering. Route the crystal (up to 16MHz) within 10 mm of XTAL1/XTAL2 with short ground returns and guard with a ground pour to reduce jitter and EMI. Because ISP uses the SPI pins, add a 2x3 ISP header footprint in production layouts so firmware can be flashed and updated after assembly without socketing the MCU.
Two substitution pitfalls: (1) the ATMEGA325P picoPower variant, while pin-compatible, differs in some register/power-management behavior - recompile firmware and verify sleep current tests; (2) the ATMEGA3250 variants share the footprint but expose additional ports, so board test coverage written for the 325 will not exercise 3250-specific pins. Also remember EEPROM writes block the CPU - schedule calibration writes outside real-time critical loops to avoid missed UART timing.
Compliance Information
Compliance certificates were not present in the verified web data; confirm RoHS/REACH status on the official Microchip product page before regulatory submissions.
