ATMEGA325A-MNR - 8-bit AVR MCU 20MHz 32KB Flash 64-QFN | Microchip
MPN: ATMEGA325A-MNR ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $1.94 | $1.94 |
| 10 | $1.86 | $18.60 |
| 100 | $1.75 | $175.00 |
| 500 | $1.65 | $825.00 |
| 1,000 | $1.55 | $1,550.00 |
ATMEGA325A-MNR Overview
An 8-bit AVR microcontroller is a Harvard-architecture processor that separates program memory (Flash) from data memory (SRAM), allowing the CPU to fetch instructions and data simultaneously. MCUs of this class sit at the center of embedded system design, integrating CPU, memory, timers, communication peripherals, and analog functions on a single chip, replacing multi-chip discrete solutions in cost- and space-sensitive products.
Key features of the ATMEGA325A include 54 general-purpose I/O lines, 32 general-purpose working registers, JTAG for on-chip debugging and boundary scan, and read-while-write Flash capability that allows firmware self-programming. The A-variant is Microchip's refresh of the original ATmega325 with improved speed and power characteristics while retaining full code compatibility.
The AVR core combines a rich instruction set with single-cycle execution, and the integrated peripheral set typically includes 8-bit and 16-bit timers with PWM outputs, a 10-bit ADC, USART serial port, and SPI-compatible interface, enabling compact designs for sensing, control, and communication tasks without external companion ICs.
Typical applications include industrial control panels, consumer appliances, battery-powered instrumentation, and building automation nodes, where the combination of 32 KB program space, in-system programmability, and wide availability makes the ATMEGA325A a dependable main controller.
When designing with this device, verify the operating voltage range and detailed peripheral specifications against the official Microchip datasheet, and use the JTAG interface for production debugging. Account for the exposed-pad QFN footprint in PCB layout for grounding and thermal relief.
This page synthesizes distributor pricing, drop-in family alternatives, and practical design notes not found in the manufacturer datasheet.
Drop-in alternatives for ATMEGA325A-MNR — 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 ATMEGA325A-MNR (same form factor and footprint) — differing in Debug Interface, Package, Packaging, RoHS Status.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
ATMEGA325A-MN
✅ Drop-In✓ In Stock
$3.17 / Unit
View Datasheet →ATMEGA325PA-MUR
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$1.65 / Unit
View Datasheet →ATMEGA325-16MUR
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$3.28 / Unit
View Datasheet →ATMEGA3250A-MUR
✅ Drop-In ⚠️ 参数待验证📋 Reference alternative (not in catalog)
ATMEGA3250PA-MUR
✅ Drop-In ⚠️ 参数待验证📋 Reference alternative (not in catalog)
ATMEGA325A-MNR Maximum Ratings & Electrical Characteristics
| Core Processor | AVR |
| Core Size | 8-Bit |
| Speed | 20 MHz |
| Flash Memory | 32 KB (16K x 16) |
| SRAM | 2 KB |
| EEPROM | 1 KB |
| Number of I/O | 54 |
| Operating Temperature | -40C to +105C |
| Package | 64-QFN (9x9 mm), Exposed Pad |
| Mounting Type | Surface Mount |
| Architecture | Harvard, RISC |
| Working Registers | 32 x 8-bit general purpose |
| Debug Interface | JTAG (on-chip debug and boundary scan) |
| Programmability | ISP (In-System Programmable), read-while-write |
| RoHS Status | Compliant (per distributor listings) |
| Packaging | Tape & Reel (R suffix) |
ATMEGA325A-MNR 64-qfn (9x9 mm), exposed pad Pin Configuration Guide
Pin configuration for ATMEGA325A-MNR (64-qfn (9x9 mm), 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 ATMEGA325A-MNR.
Refer to the datasheet for full pin configuration.
Typical Applications
ATMEGA325A-MNR is suitable for 6 applications: Industrial Control Panels, Battery-Powered Instrumentation, Consumer Appliances, Building Automation Nodes, Sensor Hubs and Data Loggers, Automotive Cabin and Body Electronics (Non-Safety).
Industrial Control Panels
The ATMEGA325A-MNR fits industrial control and panel-meter applications where its -40C to +105C operating range tolerates hot enclosures and its 32 KB Flash accommodates protocol stacks and HMI logic in a single chip. The 54 GPIO lines drive relays, LEDs, and keypads directly, while the USART and SPI interfaces link to RS-485 transceivers for Modbus-style fieldbus communication. Its JTAG interface supports on-chip debugging through the full product lifecycle, which matters for the 64-QFN package where physical pin access is impractical. Using the read-while-write Flash capability, field firmware updates can be performed over the serial link without a programming fixture, reducing maintenance cost in installed-base equipment.
Recommended
Battery-Powered Instrumentation
For portable meters, loggers, and handheld instruments, the ATMEGA325A-MNR offers multiple sleep modes and a single-supply AVR design that minimizes component count on the power tree. Where the deepest sleep current is the binding constraint, the firmware- and footprint-compatible picoPower sibling ATMEGA325PA-MUR provides microamp-level power-down current without PCB change, enabling a dual-sourcing strategy within the same layout. The 10-bit ADC and internal reference support direct sensor connection, while Timer/Counter PWM channels drive buzzers and backlight control efficiently. At 20 MHz maximum clock, designers can scale frequency with workload to trade speed against active current, extending battery life in intermittent-duty measurement applications.
Recommended
Consumer Appliances
White goods, small appliances, and climate-control products use the ATMEGA325A-MNR as a main controller where its 32 KB Flash holds menus, motor-control state machines, and safety interlock code, and its 1 KB EEPROM stores calibration and user settings through power cycles. The 64-QFN (9x9 mm) exposed-pad package keeps board area compact for cost-driven consumer PCBs, and the R suffix reel packaging suits high-volume SMT placement. The AVR single-cycle RISC core executes the interrupt-driven user-interface logic responsively even at reduced clock frequencies for EMI control. The 105C rating provides margin in enclosed housings near motors or heating elements, a common constraint in appliance electronics.
Recommended
Building Automation Nodes
Occupancy sensors, damper controllers, and room-control modules benefit from the ATMEGA325A-MNR's combination of 54 GPIO for switch and LED matrices, USART for network attachment, and EEPROM for node addressing and configuration retention. The JTAG boundary-scan capability supports production board test in panelized building-automation assemblies, catching solder defects on the fine-pitch 64-QFN before enclosure. The A-variant firmware compatibility with earlier ATmega325 code lets OEMs refresh legacy nodes without requalification of application logic. Because networked nodes run for years unattended, the read-while-write self-programming feature permits field updates of communication firmware over the bus, extending deployed product life.
Recommended
Sensor Hubs and Data Loggers
The ATMEGA325A-MNR serves as a sensor-hub MCU collecting data from analog and digital sensors through its ADC and SPI/USART peripherals, buffering results in 2 KB SRAM, and timestamping them with its timer resources. The 32 KB Flash comfortably holds a lightweight FAT or ring-buffer logging scheme plus a serial command interface. Designers commonly clock the AVR from an external crystal for timing accuracy in loggers, exploiting the full 20 MHz capability when burst-processing is needed and idling at lower clocks otherwise. The exposed-pad QFN grounds cleanly for analog-noise performance, and the 105C range permits logging inside machinery and vehicles where ambient temperatures exceed consumer-grade limits.
Recommended
Automotive Cabin and Body Electronics (Non-Safety)
Non-safety body functions such as seat-memory controllers, lighting mood modules, and climate user panels operate in the -40C to +105C envelope of the ATMEGA325A-MNR, making the industrial-grade part a fit for cabin zones away from engine-bay extremes. The 54 GPIO support switch matrices, LIN-style UART links, and LED PWM channels without expansion ICs, and 1 KB EEPROM retains learned positions and user preferences across power cycles. Note that this commercial/industrial-grade part is not AEC-Q100 qualified; for applications with formal automotive qualification requirements, select a dedicated automotive-grade AVR instead. For cost-driven cabin accessories, however, the 20 MHz throughput and rich peripheral set reduce BOM count substantially.
Recommended
Recommended Products Summary
Engineering reference data for ATMEGA325A-MNR — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ATMEGA325A-MN | ATMEGA325PA-MUR | ATMEGA325-16MUR | ATMEGA3250A-MUR |
|---|---|---|---|---|---|
| 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 |
| Flash Memory | 32 KB | 32 KB | 32 KB | 32 KB | 32 KB |
| SRAM | 2 KB | 2 KB | 2 KB | 2 KB | 2 KB |
| Maximum Clock Speed | 20 MHz | 20 MHz | 20 MHz | 16 MHz | 20 MHz |
| Low-Power Technology | Standard AVR | Standard AVR | picoPower | Standard AVR | Standard AVR |
| General Purpose I/O | 54 | 54 | 54 | 54 | Higher pin-count variant (more I/O) |
Key Differentiators
- Highest speed grade in the family (vs ATMEGA325-16MUR)
- Lower standby power option available via pin-compatible sibling (vs ATMEGA325PA-MUR)
- Consolidated A-refresh replacing older P steppings (vs ATMEGA325A-MN)
Design Notes
The 64-QFN (9x9 mm) package has a 0.5 mm pitch and an exposed pad that must be soldered to a grounded thermal pad on the PCB. Use a via array (typically 4x4 or larger) under the exposed pad connected to the ground plane to ensure reliable soldering and low-impedance ground return. Follow IPC-7351 footprint guidelines for QFN assembly, and consider the reel packaging (-MNR) for automated lines, with tray packaging (-MN) for prototyping.
Decouple VCC and AVCC pins with 100 nF ceramic capacitors placed within 2 mm of each pin pair, plus a bulk 10 uF capacitor near the device. Connect AVCC to VCC through a low-pass filter (e.g., 10 ohm resistor plus 100 nF) when the ADC is used with precision sensors, and keep the AGND star-connected to prevent digital switching noise from corrupting ADC readings. For the ADC, keep analog traces away from the crystal and fast digital lines.
Do not assume pin-compatibility outside the ATmega325 family: the ATmega3250 parts use different port mapping despite the shared 32 KB memory map. Verify the operating voltage versus frequency graph in the Microchip datasheet before running 20 MHz, since maximum clock derates at lower supply voltages. Also confirm the exact EEPROM endurance and Flash write cycles in the datasheet revision current at design time, and use the JTAG interface for debugging the QFN package, where bed-of-nails access is impossible.
Compliance Information
RoHS compliance per distributor listings; formal REACH/halogen statements should be confirmed on the Microchip product page. Not an automotive AEC-Q100 qualified part.
