ATMEGA325-16MUR - 8-bit AVR MCU 32KB 16MHz QFN-64 | Microchip
MPN: ATMEGA325-16MUR β Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $5.12 | $5.12 |
| 10 | $4.61 | $46.10 |
| 100 | $4.1 | $410.00 |
| 500 | $3.69 | $1,845.00 |
| 1,000 | $3.28 | $3,280.00 |
ATMEGA325-16MUR Overview
An 8-bit microcontroller is a single-chip computer integrating a processor core, program memory, data memory, and peripherals on one die. Within the power-management hierarchy of an embedded system, the MCU sits at the heart of the control layer: it reads sensors, executes firmware, and drives actuators. The AVR ATmega family popularized this category with its advanced RISC architecture, where most of the 131 powerful instructions execute in a single clock cycle, delivering up to 16 MIPS throughput at 16MHz.
Key features of the ATMEGA325-16MUR include 32KB self-programmable flash, 1KB EEPROM, and 2KB internal SRAM for data storage. Connectivity is provided through SPI and UART/USART serial interfaces plus USI, while on-chip peripherals include brown-out detection/reset, power-on reset, PWM outputs, and a watchdog timer. The 4.5V to 5.5V supply range makes the 16MHz speed grade well suited to robust 5V industrial logic levels with superior noise margins.
Technically, the AVR core uses a Harvard architecture with separate program and data buses, single-cycle ALU operation, and 32 general-purpose working registers directly connected to the ALU. This eliminates the arithmetic bottleneck typical of accumulator-based 8-bit cores. In-system programmable flash allows firmware updates on the assembled PCB via SPI.
Typical applications include industrial automation controllers, building automation and HVAC nodes, and test-and-measurement instruments, all of which benefit from the 5V noise immunity, rich I/O count, and mature AVR toolchain ecosystem.
A key design consideration: at 16MHz the part requires the 4.5V-5.5V supply range; lower-voltage designs must derate clock speed per the AVR frequency-voltage curve.
This page synthesizes distributor pricing, same-family drop-in alternatives, and practical design notes not found in the manufacturer datasheet.
Drop-in alternatives for ATMEGA325-16MUR 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 ATMEGA325-16MUR (same form factor and footprint) β differing in Package, Number of I/O, Instructions, Operating Temperature, EEPROM Size.
Quick Comparison Tool β Select alternative parts for side-by-side comparison:
ATMEGA325P-16MUR
β Drop-In β οΈ εζ°εΎ ιͺθ―π Reference alternative (not in catalog)
ATMEGA645-16MUR
β Drop-In β οΈ εζ°εΎ ιͺθ―β In Stock
$3.35 / Unit
View Datasheet βATMEGA329-16MUR
β Drop-In β οΈ εζ°εΎ ιͺθ―β In Stock
$3.95 / Unit
View Datasheet βAT90CAN32-16MUR
β Drop-Inπ Reference alternative (not in catalog)
ATMEGA325-16MUR Maximum Ratings & Electrical Characteristics
| Core Processor | AVR |
| Core Size | 8-Bit |
| Speed | 16 MHz |
| Program Memory Size | 32KB (16K x 16) |
| Program Memory Type | FLASH (ISP) |
| EEPROM Size | 1KB |
| RAM Size | 2KB |
| Supply Voltage Range | 4.5 V to 5.5 V |
| Number of I/O | 54 |
| Connectivity | SPI, UART/USART, USI |
| Peripherals | Brown-out Detect/Reset, POR, PWM, WDT |
| Instructions | 131 powerful instructions, mostly single-cycle |
| Package | 64-QFN (9x9 mm) with exposed pad |
| Mounting Type | Surface Mount |
| Life Cycle Stage | ACTIVE |
ATMEGA325-16MUR 64-qfn (9x9 mm) with exposed pad Pin Configuration Guide
Pin configuration for ATMEGA325-16MUR (64-qfn (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 ATMEGA325-16MUR.
Refer to the datasheet for full pin configuration.
Typical Applications
ATMEGA325-16MUR is suitable for 6 applications: Industrial Automation Controllers, Building Automation and HVAC Nodes, Test and Measurement Instruments, Motor and Actuator Control, Security and Access Control Panels, Embedded Educational and Legacy AVR Designs.
Industrial Automation Controllers
The ATMEGA325-16MUR fits industrial controller boards because its 4.5V-5.5V supply range aligns with legacy 5V industrial logic levels, delivering superior noise margin on electrically noisy factory floors. Its 54 I/O lines directly drive relay banks, optocoupler inputs, and HMI buttons without port expanders, while the 16MHz AVR core executes most of its 131 RISC instructions in a single cycle for deterministic control loops. Typical topology places the MCU between isolated RS-485/SPI field-bus transceivers and power drivers; the brown-out detector and watchdog timer guarantee recovery from supply sags caused by inrush events on shared 24V-derived rails. Because flash is in-system programmable over SPI, firmware can be updated on installed controllers without desoldering, and the 2KB SRAM accommodates modest protocol buffers and PID state variables typical of machine-control firmware.
Recommended
Building Automation and HVAC Nodes
In building automation, the ATMEGA325-16MUR serves as the main controller for thermostat, damper, and fan-coil boards. The 32KB flash holds communication stacks and control state machines, while 1KB EEPROM stores calibration constants and setpoints that must survive power loss. The 5V supply tolerance simplifies interfacing with legacy 5V sensors and triac-driving circuits common in HVAC hardware. SPI and UART/USART interfaces connect to display drivers and RS-485 gateways, and USI supports cost-reduced two-wire links to peripheral ICs. PWM outputs drive proportional valve or blower control with no external timer ICs. The 64-QFN 9x9 mm exposed-pad package provides a compact footprint and low thermal resistance path for conduction into the PCB, and the active brown-out/POR supervision ensures deterministic restart after utility power interruptions in unattended installations.
Recommended
Test and Measurement Instruments
Bench instruments, cable testers, and handheld meters benefit from the ATMEGA325-16MUR's combination of 54 I/O and single-cycle RISC execution. The 16MHz clock provides 16 MIPS throughput for timing-critical measurement routines, while the USART streams results to a host PC and SPI interfaces to precision ADCs and digital potentiometers. The 32KB in-system-programmable flash supports field firmware updates as measurement features evolve, and 2KB SRAM buffers acquisition data between interrupts. Because the AVR core has deterministic single-cycle instruction timing, measurement sequencing is predictable, easing time-budget analysis. The watchdog timer guards against firmware lockups in long-running automated test sequences, and the 5V I/O rails directly interface with legacy TTL-compatible front-panel logic common in instrument designs.
Recommended
Motor and Actuator Control
The ATMEGA325-16MUR drives DC and stepper motor subsystems using its hardware PWM channels, eliminating external PWM generator ICs. At 16MHz, PWM resolution and carrier frequencies are sufficient for quiet fan, pump, and actuator control; the 54 I/O lines interface limit switches, encoders, and H-bridge enable lines directly at 5V logic. The brown-out detector prevents corrupt PWM states during supply dips that would otherwise shoot through power FETs, and the watchdog timer enforces firmware recovery in unattended equipment. Firmware typically runs a fixed-timestep control loop reading the USART or SPI command stream while updating compare registers for speed and position control. The exposed-pad QFN-64 package conducts switching-logic heat into the PCB ground plane, supporting compact motor-driver boards without added heatsinking at these low MCU power levels.
Recommended
Security and Access Control Panels
Access-control and alarm panels use the ATMEGA325-16MUR to scan keypad matrices, supervise door sensor loops, and drive sounders and relays. The 54 I/O lines handle a 4x4 keypad, multiple supervised zones, and LED indicators without expansion hardware, while 1KB EEPROM retains user codes and event logs through power outages. The USART connects to RS-485 panels or GSM communicators, and SPI links to real-time clocks and RFID reader front ends. The 5V operating range interfaces cleanly with legacy alarm-system signaling voltages. Brown-out reset and power-on reset guarantee tamper-resistant, deterministic startup, and the watchdog timer restores supervision routines if firmware stalls. The 64-QFN exposed-pad package supports compact panel PCBs with four-layer grounding for EMI robustness near radio communicators.
Recommended
Embedded Educational and Legacy AVR Designs
The ATmega325 remains a popular target for teaching embedded systems and for maintaining installed legacy AVR designs. The classic AVR architecture with 32 working registers, single-cycle execution, and in-system programming over SPI makes it straightforward to teach in AVR Studio/Microchip Studio with common ISP programmers, and community toolchains such as MegaCore extend Arduino-style support to ATmega325-family parts. Maintenance engineers value the part for keeping older product lines alive: it is active in lifecycle status, still stocked by major distributors, and pin-compatible with picoPower and higher-memory family variants, enabling drop-in upgrades of deployed hardware. The 5V I/O levels also match through-hole era peripherals, breadboards, and legacy sensor modules common in educational laboratories and retrofit projects.
Recommended
Recommended Products Summary
Engineering reference data for ATMEGA325-16MUR β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ATMEGA325P-16MUR | ATMEGA645-16MUR | ATMEGA329-16MUR | AT90CAN32-16MUR |
|---|---|---|---|---|---|
| Package | 64-QFN (9x9 mm) | 64-QFN (9x9 mm) - same | 64-QFN (9x9 mm) - same | 64-QFN (9x9 mm) - same | 64-QFN (9x9 mm) - same |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Program Memory (Flash) | 32KB (16K x 16) | 32KB (16K x 16) | 64KB (32K x 16) | 32KB (16K x 16) | 32KB (16K x 16) |
| Max Clock Speed | 16 MHz | 16 MHz | 16 MHz | 16 MHz | 16 MHz |
| Number of I/O | 54 | 54 | 54 | 43 | 53 |
| 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 | 4.5 V to 5.5 V |
| Special Peripherals | BOD, POR, PWM, WDT; SPI/USART/USI | Same + picoPower sleep modes | Same peripherals, 4KB SRAM | Segment LCD controller added | CAN 2.0A/B controller added |
| EEPROM | 1KB | 1KB | 2KB | 1KB | 1KB |
Key Differentiators
- Highest general-purpose I/O density in the 64-pin ATmega325 family (vs ATMEGA329-16MUR)
- Same footprint with double the code space available (vs ATMEGA645-16MUR)
- Lower-power modern alternative on the same pins (vs ATMEGA325P-16MUR)
Design Notes
The 16MHz speed grade of the ATmega325 requires a 4.5V-5.5V supply per the AVR frequency-versus-voltage relationship; do not attempt 3.3V operation at 16MHz. Estimated: a typical active ICC on the order of tens of milliamps at 16MHz/5V means a 5V linear regulator dropping from 12V dissipates roughly 350mW at 50mA load - choose a regulator accordingly. Decouple VCC and AVCC independently with 100nF ceramics at each pin pair plus 10uF bulk, and connect AVCC to VCC through a low-pass LC filter when using the ADC in noisy industrial environments.
The 64-QFN (9x9 mm) exposed pad must be soldered to a grounded thermal pad array on the PCB - this pad is the primary ground return and thermal path for the die. Use a 4x4 or 5x5 via array under the pad tied to the ground plane. For rework-friendly assembly, follow Microchip QFN land-pattern recommendations with slightly extended pads to allow fillet inspection. Keep the 16MHz crystal or ceramic resonator traces under 10-15mm and guard them with ground pour, since long XTAL traces are susceptible to coupled switching noise from PWM outputs.
Three frequent issues with this family: (1) forgetting to enable the brown-out detector fuse in systems driving power FETs or relays - corrupted EEPROM and latch-up risk during brown-outs; set BODEN and appropriate BODLEVEL fuses. (2) Programming interfaces: ISP shares pins with application circuitry - insert series resistors on MOSI/MISO/SCK/RESET so in-system programming works with the target circuit attached. (3) The USI and USART are distinct peripherals; do not assume UART code runs on USI without a software-layer change. Always verify fuse settings with a programmer readback before production flashing.
Compliance Information
Compliance attributes were not stated in the verified web data retrieved for this part; verify against the official Microchip product page and environmental datasheet before procurement. Related listings (e.g., ATMEGA325-16MU on Abacus) indicate EU RoHS/REACH compliant, but this was not stated for the MUR suffix specifically.
