ATMEGA645A-AUR - 8-bit AVR MCU 64KB Flash 16MHz TQFP-64 | Microchip
MPN: ATMEGA645A-AUR ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $6.39 | $6.39 |
| 10 | $5.85 | $58.50 |
| 100 | $5.42 | $542.00 |
| 500 | $5.05 | $2,525.00 |
| 1,000 | $4.68 | $4,680.00 |
ATMEGA645A-AUR Overview
An 8-bit AVR microcontroller is a single-chip computer built around the AVR enhanced RISC architecture, executing most instructions in a single clock cycle. Within the semiconductor hierarchy it belongs to the microcontroller (MCU) category under embedded processors, positioned as a mid-density member of the megaAVR family that spans flash sizes from 16 KB to 256 KB. MCUs of this class integrate CPU, program memory, data memory, timers, ADC, serial interfaces, and an on-chip LCD controller in one package, replacing multi-chip solutions in embedded designs.
Key features include a 16 MHz maximum operating frequency delivering up to 16 MIPS, 1 KB internal SRAM-backed plus external memory interfacing through the xmem bus on ports A and C, a 10-bit ADC with up to 8 single-ended channels, and an integrated segment-driver LCD controller with up to 25 segment outputs - a distinguishing feature versus LCD-less siblings such as ATmega64. The device also provides two USARTs, SPI, two-wire interface (I2C), a 16-bit Timer/Counter1, two 8-bit timers, an analog comparator, and JTAG for on-chip debugging and boundary scan.
Architecturally, the AVR core uses 32 general-purpose working registers directly connected to the ALU, allowing one-cycle execution and efficient C compilation. Read-while-write FLASH supports self-programming for boot-loader firmware updates. The picoPower-inherited A-series die offers improved power efficiency over the original ATmega645, with operating voltage from 2.5 V to 5.5 V per the datasheet family range.
Typical applications include industrial instrumentation with segment LCD displays, battery-powered metering, building automation panels, and consumer appliance human-machine interfaces, where the combination of LCD drive, 64 KB code space, and low idle power is decisive.
Design consideration: the LCD controller shares port pins with general I/O; if the LCD is unused, configure the LCDCR registers for full GPIO use and validate the 32.768 kHz timer oscillator routing for RTC accuracy.
This page adds value beyond the manufacturer datasheet by consolidating verified distributor pricing, drop-in family alternatives, application pairings, and practical design notes in one AI-citable reference.
Drop-in alternatives for ATMEGA645A-AUR — 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 ATMEGA645A-AUR (same form factor and footprint) — differing in EEPROM, Package, SRAM, Flash Memory, Operating Temperature.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
ATMEGA645A-AU
✅ Drop-In✓ In Stock
$3.95 / Unit
View Datasheet →ATMEGA645-16AUR
✅ Drop-In✓ In Stock
$5.4 / Unit
View Datasheet →ATMEGA6450A-AU
✅ Drop-In✓ In Stock
$5.95 / Unit
View Datasheet →ATMEGA649A-AU
✅ Drop-In📋 Reference alternative (not in catalog)
ATMEGA645-16AI
✅ Drop-In✓ In Stock
$6.45 / Unit
View Datasheet →ATMEGA640-16AUR
✅ Drop-In✓ In Stock
$5.9 / Unit
View Datasheet →ATMEGA645A-AUR Maximum Ratings & Electrical Characteristics
| Core Architecture | 8-bit AVR RISC |
| Max Operating Frequency | 16 MHz |
| Flash Memory | 64 KB (32K x 16) ISP FLASH |
| EEPROM | 2 KB |
| SRAM | 4 KB |
| Operating Voltage Range | 2.5 V / 3.3 V / 5 V (per datasheet family listing) |
| General Purpose I/O | 54 I/O lines |
| Working Registers | 32 x 8-bit |
| ADC | 10-bit, 8 channels |
| LCD Controller | Yes, segment driver (megaAVR LCD family) |
| Timers | Two 8-bit, one 16-bit |
| Serial Interfaces | 2 x USART, SPI, TWI (I2C compatible) |
| Debug / Programming | JTAG, ICSP (In-Circuit Serial Programming) |
| Package | 64-TQFP (14 x 14 mm) |
| Operating Temperature (Max) | 85 C |
| Mounting Type | Surface Mount |
| Packaging | Tape & Reel (R suffix) |
| RoHS Status | Compliant |
ATMEGA645A-AUR 64-tqfp (14 x 14 mm) Pin Configuration Guide
Pin configuration for ATMEGA645A-AUR (64-tqfp (14 x 14 mm) 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 ATMEGA645A-AUR.
Refer to the datasheet for full pin configuration.
Typical Applications
ATMEGA645A-AUR is suitable for 6 applications: Segment LCD Instrumentation Panels, Battery-Powered Metering and Data Loggers, Building Automation Control Nodes, Appliance Human-Machine Interfaces, Portable Test and Measurement Instruments, Access Control and Security Keypads.
Segment LCD Instrumentation Panels
The ATMEGA645A-AUR fits utility meters, HVAC controllers, and industrial panel meters because its integrated LCD segment driver eliminates a standalone LCD controller IC such as a discrete 7-segment driver chain, saving board area and BOM cost. The 10-bit ADC with 8 channels digitizes sensor inputs directly, while the 64 KB FLASH leaves ample room for multi-language display tables and communication stacks. In a typical circuit the LCD runs from the internal 32.768 kHz-synchronized controller with software-set duty and bias, and the remaining ports drive relays and keys. Unlike solutions pairing a small MCU with an external driver, this integration cuts quiescent current and removes an I2C bus failure point, at the cost of reserving shared GPIO for LCD use.
Recommended
Battery-Powered Metering and Data Loggers
For battery-operated water, heat, and energy meters, the ATMEGA645A-AUR combines a wide 2.5 V to 5.5 V operating range with the megaAVR idle and power-down sleep modes, allowing multi-year coin-cell or lithium-thionyl-chloride operation. The 2 KB EEPROM stores accumulated consumption and calibration constants through power cycles without external NVRAM, and the 4 KB SRAM buffers logged samples. The on-chip LCD stays active in low-power states so consumption is continuously visible. Placed in a 64-TQFP with RTC sourced from a 32.768 kHz crystal, the design achieves a duty-cycled profile where sleep current dominates battery budget; engineers should size pull-ups and LCD bias networks carefully, as they often exceed MCU sleep current by an order of magnitude.
Recommended
Building Automation Control Nodes
The ATMEGA645A-AUR suits room controllers, damper actuators, and thermostat nodes where a small display meets moderate control logic. The two USARTs permit simultaneous RS-485 fieldbus (via external transceiver) and a service/debug port; the TWI interface reads humidity or temperature sensors over I2C. JTAG enables production boundary-scan testing of the dense 64-pin board and on-chip debugging during firmware bring-up with MPLAB SNAP or JTAGICE tools. Its 64 KB FLASH accommodates a Modbus RTU stack plus PID control loops with headroom for OTA boot-loader code, leveraging read-while-write FLASH to update firmware without losing RAM state. The trade-off versus ARM Cortex-M0 parts is lower clock performance, but the single-cycle AVR core and deterministic interrupts simplify real-time control.
Recommended
Appliance Human-Machine Interfaces
In ovens, washing machines, and coffee machines, the ATMEGA645A-AUR drives the segment or bar-graph LCD, scans the key matrix, controls relays or TRIAC firing through port pins, and monitors a thermistor via the 10-bit ADC - all in one 64-TQFP. The 85 C maximum operating rating covers typical appliance ambient conditions near the control board, though parts adjacent to heating elements need thermal derating review. The A-series die's improved efficiency helps with always-on clock display requirements. Firmware benefits from the 2 KB EEPROM for cycle counters and user preferences. Compared with a two-chip MCU-plus-LCD-driver approach, the single-chip solution shortens the display update path and removes inter-chip communication latency, which visibly improves key-press responsiveness on low-cost designs.
Recommended
Portable Test and Measurement Instruments
Handheld capacitance, insulation-resistance, and environmental meters benefit from the ATMEGA645A-AUR's ADC, LCD driver, and JTAG debug in a compact 14 x 14 mm TQFP. The 8-channel 10-bit ADC samples sensor front-ends, while software oversampling extends effective resolution for quasi-static measurements - a common AVR technique trading sample rate for bits. The 64 KB FLASH holds calibration tables, USB or UART reporting firmware, and multi-range scaling logic. Sleep-mode operation between readings extends battery service intervals, and the integrated LCD keeps measurement output live even in deep sleep profiles. Designers should route the ADC ground reference away from LCD drive lines, since segment-driver switching injects small charge spikes that can degrade sub-LSB measurement repeatability without careful layout.
Recommended
Access Control and Security Keypads
Door controllers and alarm keypads use the ATMEGA645A-AUR to combine a status LCD, keypad scanning across the plentiful GPIO, EEPROM-backed credential or code storage, and a USART link to the central panel over RS-485. The 54 I/O lines support a 4x4 or larger key matrix plus backlight and buzzer control while still driving the display. The 64 KB FLASH holds encryption routines (AES software implementations fit comfortably) for challenge-response authentication with the master controller. JTAG boundary scan supports ICT coverage on the dense keypad PCB. Against simpler no-display controllers, the integrated LCD removes an external driver; against Linux-based touch panels, this part wins on boot time (milliseconds), cost, and deterministic watchdog behavior required for fail-secure door logic.
Recommended
Recommended Products Summary
Engineering reference data for ATMEGA645A-AUR — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ATMEGA645A-AU | ATMEGA645-16AUR | ATMEGA6450A-AU | ATMEGA649A-AU | ATMEGA645-16AI | ATMEGA640-16AUR |
|---|---|---|---|---|---|---|---|
| Package | 64-TQFP (14 x 14 mm) | 64-TQFP - same | 64-TQFP - same | 64-TQFP - same | 64-TQFP - same | 64-TQFP - same | 64-TQFP - same |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology (Atmel) | Microchip Technology (Atmel) | Microchip Technology (Atmel) | Microchip Technology (Atmel) | Microchip Technology (Atmel) |
| Flash Memory | 64 KB | 64 KB | 64 KB | 64 KB | 64 KB | 64 KB | 64 KB |
| SRAM | 4 KB | 4 KB | 4 KB | 4 KB | 4 KB | 4 KB | 8 KB |
| EEPROM | 2 KB | 2 KB | 2 KB | 2 KB | 2 KB | 2 KB | 4 KB |
| LCD Controller | Yes, segment driver | Yes, segment driver | Yes, segment driver | Yes, wider segment count | Yes, largest segment count | Yes, segment driver | No |
| Max Clock | 16 MHz | 16 MHz | 16 MHz | 16 MHz | 16 MHz | 16 MHz | 16 MHz |
| Drop-in vs This Part | Reference | Identical (packaging variant) | Drop-in per AVR543 | Family drop-in, LCD width differs | Family drop-in, GPIO/LCD trade-off | Drop-in per AVR543 | Pin-compatible, peripheral remap needed |
Key Differentiators
- Integrated LCD segment driver with full GPIO count (vs ATMEGA649A-AU)
- A-series die power efficiency (vs ATMEGA645-16AUR)
- On-chip LCD saves an external driver IC (vs ATMEGA640-16AUR)
- JTAG on-chip debug and boundary scan (vs ATMEGA644-20AU)
Design Notes
For the 64-TQFP (0.8 mm pitch) land pattern, follow IPC-compatible SOF/TH gross dimensions from the Microchip packaging drawer and connect the die-attached paddle area (if present in the selected footprint) or leave thermal relief per the datasheet. Place 100 nF ceramic decoupling capacitors within 3 mm of each VCC pin pair (pins 17/46 region and AVCC pin 37), plus a 10 uF bulk capacitor per supply rail. Route AVCC and AREF separately from digital VCC with a ferrite bead or RC filter when ADC accuracy below 2 LSB matters, and keep LCD bias resistors away from the crystal.
The ATmega645A shares port pins between the LCD controller and general-purpose I/O. If your design uses these pins as GPIO, disable the LCD (clear LCD enable bits and set LCD-related configuration registers correctly) at reset, otherwise floating LCD drive stages cause unpredictable pin behavior and excess current. Also note the migration from ATmega645 to ATmega645A involves minor electrical characteristic changes listed in Microchip app note AVR543 (doc8423) - recheck DC characteristics and brown-out thresholds when swapping dies in existing designs.
Estimated: for a 5 V, 16 MHz active-mode configuration, typical megaAVR active current of roughly 10-15 mA yields 50-75 mW of core power, well within TQFP-64 thermal capability with no heatsink. Sleep modes dominate battery designs: budget external pull-ups, LCD bias networks, and watchdog current into the sleep budget, as they frequently exceed the microcontroller's own power-down current by an order of magnitude. Use the power-down mode with the asynchronous 32.768 kHz Timer/Counter2 running only when an RTC is required.
If the external memory interface on ports A and C (xmem) is used, keep address/data traces under 10 cm and match strobe timing per the datasheet external memory access timing tables at 16 MHz; add 22-33 ohm series resistors on the data bus to control ringing on long traces. Unused GPIO should be configured as inputs with internal pull-ups enabled or driven low outputs per Microchip's AVR hardware design considerations application guidance, to prevent floating-pin EMI and excess current in noisy industrial environments.
Compliance Information
RoHS compliance and lead-free (U suffix matte-tin) finish per distributor listings (DigiKey, Mouser, Datasheets.com). REACH, halogen-free, and conflict-minerals declarations not present in provided data - obtain from Microchip environmental documentation.
