ATMEGA3250A-AU - 8-bit AVR MCU 32KB 20MHz TQFP-100 | Microchip
MPN: ATMEGA3250A-AU ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $3.98 | $3.98 |
| 10 | $3.6 | $36.00 |
| 100 | $3.2 | $320.00 |
| 500 | $2.85 | $1,425.00 |
| 1,000 | $2.5 | $2,500.00 |
ATMEGA3250A-AU Overview
An 8-bit microcontroller is an integrated circuit that executes programs and controls electronic systems using an 8-bit data bus and an AVR enhanced RISC architecture. Within the product hierarchy, the ATmega3250A belongs to the AVR ATmega family of flash-based MCUs, which sits under the broader categories of embedded processors and semiconductor integrated circuits. AVR MCUs execute most instructions in a single clock cycle, delivering throughput near 1 MIPS per MHz.
Key features include 131 powerful instructions with mostly single-cycle execution, 32 general purpose I/O ports with up to 68 programmable I/O lines, two USARTs, SPI and TWI (I2C) serial interfaces, and a JTAG boundary-scan and on-chip debug interface. The device also integrates an 8-channel 10-bit ADC, analog comparator, three timers (two 8-bit and one 16-bit), and a programmable watchdog timer with separate on-chip oscillator.
Technically, the ATmega3250A uses the AVR advanced RISC core with 32 general-purpose working registers directly connected to the ALU, allowing two independent registers to be accessed in one instruction executed in one clock cycle. Program memory is In-System Programmable via SPI, and the device supports In-Application Programming and boot-code self-programming for field updates. The A-suffix device is a functionally identical drop-in replacement for the earlier ATmega3250, produced on an updated manufacturing process, as documented in Microchip application note AVR540.
Typical applications include industrial automation controllers, building and access control systems, sensor hubs, LCD-adjacent instrumentation, and motor control panels where a large number of I/O lines and 5V operation are required.
A key design consideration is supply voltage: this AU speed-grade device operates from 4.5V to 5.5V at 20MHz per the specification data, so designs running from 3.3V rails should evaluate the V-variant or reduce the clock frequency accordingly.
This page consolidates distributor pricing, drop-in same-family alternatives, and practical engineering design notes that are not presented together in the manufacturer datasheet.
Drop-in alternatives for ATMEGA3250A-AU — 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 ATMEGA3250A-AU (same form factor and footprint) — differing in Instructions, RoHS Status, Number of I/O, Operating Temperature, Package.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
ATMEGA3250PA-AU
✅ Drop-In✓ In Stock
$4.43 / Unit
View Datasheet →ATMEGA3250-16AU
✅ Drop-In✓ In Stock
$5.74 / Unit
View Datasheet →ATMEGA3290A-AU
✅ Drop-In✓ In Stock
$3.85 / Unit
View Datasheet →ATMEGA3290PA-AU
✅ Drop-In✓ In Stock
$4.48 / Unit
View Datasheet →ATMEGA3250V-8AI
✅ Drop-In📋 Reference alternative (not in catalog)
ATMEGA3250A-AU 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 |
| Supply Voltage | 4.5 V to 5.5 V |
| Number of I/O | 68 |
| I/O Ports | 32 (A-J port system) |
| Connectivity | SPI, UART/USART, TWI (I2C) |
| Peripherals | Brown-out Detect/Reset, POR, PWM, WDT |
| ADC Resolution | 10 bit |
| ADC Channels | 8 |
| Instructions | 131 (most single-cycle) |
| Debug Interface | JTAG (on-chip debug + boundary scan) |
| Package | 100-TQFP (14x14 mm), 0.8 mm pitch |
| Mounting Type | Surface Mount |
| RoHS Status | Compliant (Green) |
ATMEGA3250A-AU 100-tqfp (14x14 mm), 0.8 mm pitch Pin Configuration Guide
Pin configuration for ATMEGA3250A-AU (100-tqfp (14x14 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 ATMEGA3250A-AU.
Refer to the datasheet for full pin configuration.
Typical Applications
ATMEGA3250A-AU is suitable for 6 applications: Industrial Automation Controllers, Building Access Control and Security Panels, Sensor Hubs and Data Acquisition, Motor Control and Relay Panels, Instrumentation Front Panels, Embedded Gateways and Legacy 5V System Retrofit.
Industrial Automation Controllers
The ATMEGA3250A-AU fits industrial automation controller boards because 68 programmable I/O lines and 5V noise-tolerant rails let one MCU drive relays, optocouplers, and status LEDs without port expanders. The AVR core at up to 20MHz delivers roughly 20 MIPS, sufficient for sequential machine logic, while the 10-bit ADC samples 8 analog sensor channels for temperature and current monitoring. Two USARTs link to HMI panels and field buses simultaneously, and SPI/TWI connect EEPROM configuration stores. The JTAG interface enables boundary-scan production testing of the dense 100-TQFP board. Its 4.5V-5.5V supply matches legacy 5V industrial logic, eliminating level shifters; the trade-off is higher quiescent consumption than picoPower variants, so choose ATMEGA3250PA-AU for battery-backed nodes.
Recommended
Building Access Control and Security Panels
Access control panels require many discrete inputs (door contacts, tamper switches, keypads) and outputs (locks, sirens, indicators), which aligns directly with the ATMEGA3250A-AU's 68 I/O lines in a single 14x14 mm TQFP. The two USARTs independently service an RS-485 multidrop network and a local Wiegand or UART reader, while the 1KB EEPROM stores user credentials and event counters through power cycles. The watchdog timer with separate on-chip oscillator resets a hung panel without external components, improving availability. Brown-out detection ensures reliable EEPROM writes during mains dips. At 5V, long cable-derived noise margins are robust; the 20MHz ceiling supports fast debouncing scans. JTAG debugging shortens firmware iteration for locking-state machines.
Recommended
Sensor Hubs and Data Acquisition
The ATMEGA3250A-AU serves as a sensor hub where the 8-channel 10-bit ADC aggregates analog sensors while TWI and SPI buses poll digital sensors simultaneously. At 20MHz, the AVR converts a channel in roughly 13 ADC clock cycles (about 65 microseconds at full speed), supporting kilohertz-rate multi-channel scanning adequate for temperature, pressure, and level monitoring. Two USARTs stream formatted data to loggers or modems while a second port services configuration terminals. The 2KB SRAM buffers sample blocks for burst transfer, and boot-loader self-programming allows field firmware updates over the existing UART without removing devices from enclosures. For battery-powered wireless hubs, the picoPower ATMEGA3250PA-AU materially reduces sleep current.
Recommended
Motor Control and Relay Panels
Motor and relay control panels benefit from the ATMEGA3250A-AU's multiple PWM-capable timers (two 8-bit and one 16-bit) that generate drive signals for DC motor speed control and servo positioning without external PWM ICs. Sixty-eight I/O lines handle interlocks, limit switches, and contactor drivers directly through transistor arrays. The analog comparator enables fast over-current trip detection independent of the ADC pipeline, and the 16-bit timer captures input events for RPM measurement with microsecond resolution. Operating from 5V keeps gate-drive and optocoupler thresholds compatible with classic industrial drivers. Designers must budget the 20MHz cycle time for fault-latency paths and use the watchdog to guarantee safe shutdown on firmware lockup.
Recommended
Instrumentation Front Panels
Instrumentation products with dense keypads, encoders, and indicator clusters use the ATMEGA3250A-AU because its large port count natively matrix-scans large keypads and drives multi-digit displays through port multiplexing. The 10-bit ADC reads front-panel potentiometers for set-point adjustment with one LSB resolution over a 5V span, and TWI attaches an external real-time clock for data stamping. The 32KB Flash accommodates menu trees, calibration tables, and multiple language strings with headroom, while 1KB EEPROM persists calibration between power cycles. JTAG boundary scan simplifies testing of the high-pin-count TQFP solder joints after reflow, reducing production escapes. For portable instruments, evaluate the picoPower ATMEGA3250PA-AU to extend battery life.
Recommended
Embedded Gateways and Legacy 5V System Retrofit
Legacy industrial equipment designed around 5V logic often needs modernization without redesigning backplanes; the ATMEGA3250A-AU retrofits into these systems because its 4.5V-5.5V supply and 5V-tolerant I/O interface directly to TTL-era peripherals, opto-isolated buses, and bipolar driver logic. Two USARTs bridge an existing RS-232 service port and a new RS-485 supervisory link, while SPI attaches modern flash or Ethernet companions where available. The 20MHz operation provides timing headroom for protocol conversion, and ISP programming allows field updates through the existing connector. This avoids level-shifter complexity and reliability risks of mixed-voltage designs. New battery-sensitive designs should instead select the ATMEGA3250PA-AU with identical pinout.
Recommended
Recommended Products Summary
Engineering reference data for ATMEGA3250A-AU — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ATMEGA3250PA-AU | ATMEGA3250-16AU | ATMEGA3290A-AU | ATMEGA3250V-8AI |
|---|---|---|---|---|---|
| Package | 100-TQFP (14x14 mm) | 100-TQFP (14x14 mm) - same | 100-TQFP (14x14 mm) - same | 100-TQFP (14x14 mm) - same | 100-TQFP (14x14 mm) - same |
| Brand | Microchip Technology (Atmel) | Microchip Technology | Microchip Technology (Atmel) | Microchip Technology (Atmel) | Microchip Technology (Atmel) |
| Max Clock Speed | 20 MHz | 20 MHz | 16 MHz | 20 MHz | 8 MHz |
| Flash / SRAM / EEPROM | 32 KB / 2 KB / 1 KB | 32 KB / 2 KB / 1 KB | 32 KB / 2 KB / 1 KB | 32 KB / 2 KB / 1 KB | 32 KB / 2 KB / 1 KB |
| Supply Voltage | 4.5 V to 5.5 V | 1.8 V to 5.5 V (picoPower) | 4.5 V to 5.5 V | 4.5 V to 5.5 V | 2.7 V to 5.5 V |
| LCD Controller | No | No | No | Yes (segment LCD) | No |
| picoPower Technology | No | Yes | No | No | No |
| JTAG Debug / Boundary Scan | Yes | Yes | Yes | Yes | Yes |
Key Differentiators
- Highest standard speed grade in the family (vs ATMEGA3250-16AU)
- LCD-free pin utilization (vs ATMEGA3290A-AU)
- Simpler legacy process characteristics (vs ATMEGA3250PA-AU)
Design Notes
The ATMEGA3250A-AU is a 5V speed grade rated 4.5V-5.5V at 20MHz. Do not attempt 3.3V operation at full clock; if the rail is 3.3V, migrate to the ATMEGA3250V-8AI (2.7V-5.5V) or reduce f_CPU and verify timing against the datasheet voltage-frequency curve. Estimated: at 5V/20MHz with heavy I/O switching, active current can reach the tens-of-mA range, so size the 5V regulator with margin and place a 100nF ceramic capacitor at each of the multiple VCC/GND pin pairs of the 100-TQFP plus one 10uF bulk capacitor.
The 100-TQFP (14x14 mm, 0.8 mm pitch) requires careful escape routing. Fan out on 0.127 mm (5 mil) trace/Space if the router allows, or use two signal layers with short dog-bones. Decouple every VCC pin pair with a nearby 100nF capacitor, and connect the exposed power ring solidly to the ground plane. JTAG pins (TDI/TDO/TMS/TCK) should route to a 2x5 header for in-system debug and boundary-scan production testing, which is highly valuable at this pin count.
The A-suffix is a drop-in replacement for the original ATmega3250, but per Microchip application note AVR540 the manufacturing process differs, so some electrical characteristics (timing margins, current figures) differ slightly - re-verify critical analog measurements after migration. Also note that firmware written for the non-A part runs unchanged, but erase/program cycle limits and calibration bytes should be re-read via ISP on first power-up. Finally, do not exceed 20MHz at 5V; overclocking voids AC timing guarantees for USART and SPI baud accuracy.
Compliance Information
Distributor data (FindIC) classifies the part as Green, indicating RoHS compliance and lead-free construction. AEC-Q100 qualification is not claimed for this ordering code.
