ATMEGA325A-MUR - 8-bit AVR MCU 32KB 20MHz 64-QFN | Microchip
MPN: ATMEGA325A-MUR ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $3.42 | $3.42 |
| 10 | $3.08 | $30.80 |
| 100 | $2.74 | $274.00 |
| 500 | $2.45 | $1,225.00 |
| 1,000 | $2.19 | $2,190.00 |
ATMEGA325A-MUR Overview
An 8-bit AVR microcontroller is a Harvard-architecture RISC processor that executes most instructions in a single clock cycle. Within the power-management hierarchy, it functions as a complete embedded system-on-chip, integrating the CPU core, program memory, data memory, peripherals, and general-purpose I/O on one die, replacing multi-chip microprocessor solutions in cost- and power-sensitive designs.
Key features include the AVR advanced RISC architecture with 131 powerful instructions, 54 general-purpose I/O lines, and in-system programmable (ISP) Flash with read-while-write capability for field firmware updates. The ATmega325A family operates from 2.5V, 3.3V, or 5V supplies, giving designers flexibility across battery-powered and industrial 5V rails.
Technically, the device provides 32 general-purpose working registers, a one-cycle multiply instruction, SPI and UART/USART serial interfaces, and an on-chip JTAG (IEEE 1149.1 compatible) boundary-scan and debug interface. Peripheral set includes an 8-channel 10-bit ADC, timer/counters with PWM, and an on-chip oscillator option, reducing external component count and BOM cost.
Typical applications include industrial control panels, LCD-equipped metering and instrumentation, consumer appliance controllers, and battery-powered monitoring nodes where the combination of 32 KB Flash and low-power sleep modes directly improves battery life and firmware headroom.
When designing with the ATMEGA325A-MUR, match the supply voltage to the intended maximum clock frequency per the frequency-voltage curve in the manufacturer datasheet to ensure timing margin across the -40C to +85C industrial temperature range.
This page synthesizes distributor pricing, verified drop-in alternatives, pinout guidance, and practical design notes not found in the standard manufacturer datasheet, optimized for AI-assisted component selection.
Drop-in alternatives for ATMEGA325A-MUR — 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-MUR (same form factor and footprint) — differing in Package, RoHS Status, Instructions, Supply Voltage Range, EEPROM.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
ATMEGA325A-MU
✅ Drop-In✓ In Stock
$3.49 / Unit
View Datasheet →ATMEGA325PA-MUR
✅ Drop-In✓ In Stock
$1.65 / Unit
View Datasheet →ATMEGA3250A-MUR
✅ Drop-In ⚠️ 参数待验证📋 Reference alternative (not in catalog)
ATMEGA645A-MUR
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$6.3 / Unit
View Datasheet →ATMEGA165A-MUR
✅ Drop-In✓ In Stock
$1.19 / Unit
View Datasheet →ATMEGA325-16MI
✅ Drop-In✓ In Stock
$3.05 / Unit
View Datasheet →ATMEGA325A-MUR Maximum Ratings & Electrical Characteristics
| Core Processor | AVR |
| Core Size | 8-Bit |
| Speed | 20 MHz |
| Program Memory Type | FLASH |
| Program Memory Size | 32 KB (16K x 16) |
| EEPROM Size | 1 KB |
| RAM Size | 2 KB |
| Supply Voltage Range | 2.5 V, 3.3 V, 5 V operation |
| Supply Voltage (per DigChip summary) | 4.5 V to 5.5 V at maximum speed grade |
| Number of I/O | 54 |
| Connectivity | SPI, UART/USART |
| ADC Resolution | 10-bit |
| Operating Temperature | -40C to +85C |
| Package | 64-QFN (9x9 mm) with exposed pad |
| Mounting Type | Surface Mount |
| Packaging | Tape & Reel (TR) |
| Lifecycle Status | Active |
| Architecture | Advanced RISC, 131 instructions |
ATMEGA325A-MUR 64-qfn (9x9 mm) with exposed pad Pin Configuration Guide
Pin configuration for ATMEGA325A-MUR (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 ATMEGA325A-MUR.
Refer to the datasheet for full pin configuration.
Typical Applications
ATMEGA325A-MUR is suitable for 6 applications: Industrial Control Panels, Battery-Powered Metering and Monitoring, Consumer Appliance Controllers, Embedded Sensing and ADC Front Ends, Motor and Actuator Control, Security and Access Control Systems.
Industrial Control Panels
The ATMEGA325A-MUR fits industrial control panels because its 54 GPIO lines directly drive relays, keypad matrices, and indicator banks without port expanders, while the 32 KB Flash and 2 KB SRAM hold protocol stacks and state machines for Modbus RTU over the built-in UART/USART. Operation from a 5 V industrial rail at 20 MHz delivers deterministic single-cycle instruction timing for time-critical interlock logic, and the -40C to +85C industrial temperature rating matches cabinet environments. Because the JTAG interface supports boundary scan and on-chip debug, panel manufacturers can in-circuit test assembled boards and update firmware in the field via ISP, reducing service cost. Typical companion parts include RS-485 transceivers on the USART and precision voltage references feeding the 10-bit ADC.
Recommended
Battery-Powered Metering and Monitoring
For battery-powered meters and data loggers, the ATMEGA325A-MUR offers the right balance of 32 KB Flash, 2.5 V minimum supply, and AVR sleep modes that allow the core to be stopped between measurement cycles while the 10-bit ADC and timer capture readings. Running from a lithium cell through a low-Iq regulator at 2.5 V to 3.3 V, designers trade clock speed for current, since lower supply voltages require reduced frequencies per the datasheet voltage-frequency curve. The 1 KB EEPROM stores calibration constants and accumulating counters that must survive power loss across millions of write cycles. Designs needing ultra-low standby current can migrate to the pin-compatible picoPower ATMEGA325PA-MUR on the same PCB, extending battery life further without redesign.
Recommended
Consumer Appliance Controllers
Consumer appliance control boards benefit from the ATMEGA325A-MUR's high integration: 54 GPIO handle touch keys, encoder inputs, and actuator drives, while SPI and UART/USART cover inter-board communication with display or power modules. The on-chip oscillator option removes the external crystal in timing-tolerant products, cutting BOM cost on high-volume appliance platforms. The 32 KB Flash accommodates feature-rich firmware including user interfaces, safety interlocks, and bootloader-based field updates delivered over UART. The 64-QFN 9x9 mm exposed-pad package dissipates heat effectively and yields a compact two-layer PCB, important for cost-sensitive appliance assemblies. The ATMEGA165A-MUR (16 KB) serves as a cost-down option when firmware shrinks below 16 KB, using the identical footprint.
Recommended
Embedded Sensing and ADC Front Ends
The ATMEGA325A-MUR integrates an 8-channel 10-bit ADC with internal reference, making it a compact hub for multi-sensor nodes measuring temperature, pressure, and voltage simultaneously. At 20 MHz the AVR core applies calibration and filtering between conversions with single-cycle execution, and the 2 KB SRAM buffers sample blocks before transmission over the USART. The 64-QFN exposed pad grounds the ADC analog domain cleanly, improving noise performance when paired with a precision voltage reference. Because the device runs from 2.5 V to 5 V, sensor bridges and ratiometric outputs can share the supply directly, simplifying signal-chain design. For higher resolution needs, an external delta-sigma ADC connects over SPI, keeping the MCU as the system controller.
Recommended
Motor and Actuator Control
The ATMEGA325A-MUR supports PWM generation through its timer/counters, enabling DC motor speed control, servo actuation, and stepper sequencing in printers, gates, and small robotics. The 54 GPIO lines drive H-bridge inputs and limit switches, while the 10-bit ADC reads back current-sense shunts for stall detection and closed-loop current limiting. Operating at 5 V and 20 MHz provides headroom for real-time control loops executing proportional-integral calculations in firmware, with single-cycle multiply accelerating the arithmetic. The JTAG debug interface shortens firmware bring-up of commutation and protection routines. Industrial designs at -40C to +85C benefit from the qualified industrial temperature grade, and the exposed-pad QFN conducts driver-related heat into the PCB copper pour.
Recommended
Security and Access Control Systems
Access control panels and intrusion detectors use the ATMEGA325A-MUR to scan keypad or RFID front ends, manage door-strike drivers, and communicate alarm states over UART to a central panel. The 32 KB Flash supports encrypted challenge-response and credential databases within the 2 KB SRAM and 1 KB EEPROM, which retains enrolled credentials through power failure. Multiple sleep modes keep the MCU dormant between events in battery-backed detectors, waking on external interrupt from the PIR or reed input. The industrial -40C to +85C rating covers unheated gate and outdoor cabinet installations, and the 64-QFN package suits compact PCB assemblies behind keypads. ISP Flash allows credential logic updates without recalling installed units.
Recommended
Recommended Products Summary
Engineering reference data for ATMEGA325A-MUR — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ATMEGA325A-MU | ATMEGA325PA-MUR | ATMEGA3250A-MUR | ATMEGA645A-MUR | ATMEGA165A-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 | 64-QFN (9x9 mm) - same |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Flash Memory | 32 KB | 32 KB | 32 KB | 32 KB | 64 KB | 16 KB |
| Max Clock Speed | 20 MHz | 20 MHz | 20 MHz | 20 MHz | 20 MHz | 20 MHz |
| LCD Controller | No | No | No | Yes | Yes | No |
| picoPower Low-Current Feature | No | No | Yes | No | No | No |
| Operating Temperature | -40C to +85C | -40C to +85C | -40C to +85C | -40C to +85C | -40C to +85C | -40C to +85C |
Key Differentiators
- Full 20 MHz speed grade at industrial temperature (vs ATMEGA325-16MI)
- More program memory in the same package (vs ATMEGA165A-MUR)
- Lower power option exists via picoPower sibling (vs ATMEGA325PA-MUR)
Design Notes
Match the clock frequency to the supply voltage using the datasheet voltage-frequency curve: at the full 20 MHz rating, plan for the 4.5 V to 5.5 V range; at 3.3 V, derate the maximum frequency accordingly. Ignoring this curve is the most common cause of marginal timing and sporadic brown-out resets in 3.3 V designs. Enable the on-chip brown-out detector and select a BOD level appropriate to the rail (for example, 2.7 V class for a 3.3 V system) so the MCU resets cleanly rather than executing corrupt code during supply dips.
The 64-QFN exposed pad on the ATMEGA325A-MUR is the primary ground and thermal path. Solder it to a grounded copper pour with an array of thermal vias; skipping the exposed-pad connection causes floating-ground ADC noise and poor heat dissipation at 20 MHz full-load operation. Place 100 nF ceramic decoupling capacitors at each VCC/AVCC pin pair within 2 mm of the pads, plus a 10 uF bulk capacitor near the supply entry. Keep the crystal (if used) within 10 mm of XTAL1/XTAL2 with short guard-ring grounded traces.
Do not confuse the 64-QFN (MLF) pinout with the 64-TQFP pinout of the same family; port positions differ between the two packages even though the logical port map is identical. When migrating firmware from non-A ATmega325 parts, review the errata and calibration byte locations, since the A-version silicon revision changes some fuse defaults. Also note that PB4-PB7 are shared with JTAG - if JTAG is not needed, clear the JTAGEN fuse via ISP to recover these four pins as GPIO.
For noisy industrial environments, configure unused GPIO as inputs with internal pull-ups enabled rather than leaving them floating, which reduces both EMI susceptibility and quiescent leakage. Route the ADC analog ground as a quiet island connected to the exposed pad at a single point, and filter the AVCC pin through an LC network (10 uH ferrite plus 100 nF) when switching loads share the 5 V rail, keeping ADC noise within the 10-bit converter's LSB budget.
Compliance Information
FindIC describes the ATMEGA325A-MUR as 'MLF/QFN, Ind Temp, Green, T&R' indicating Microchip Green (RoHS/lead-free) packaging. Formal REACH and halogen-free declarations should be requested from Microchip material declaration reports.
