ATMEGA645-16AI - 8-bit AVR MCU 64KB Flash 16MHz | Microchip
MPN: ATMEGA645-16AI ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $9.42 | $9.42 |
| 10 | $8.55 | $85.50 |
| 100 | $7.68 | $768.00 |
| 500 | $7.1 | $3,550.00 |
| 1,000 | $6.45 | $6,450.00 |
ATMEGA645-16AI Overview
A microcontroller of this class combines a processor core, program memory, data memory, and peripherals on a single chip, sitting at the device level of the semiconductor hierarchy: ATmega645 -> AVR 8-bit MCU -> microcontroller -> embedded processor. Such MCUs replace multi-chip CPU, RAM, and ROM solutions in cost-sensitive embedded designs where single-cycle instruction execution simplifies timing-critical code.
Key features include the advanced AVR RISC architecture with 130 powerful instructions, most executing in a single clock cycle; 32 general-purpose working registers directly connected to the ALU; In-System Programmable (ISP) Flash for field firmware updates; and on-chip JTAG for boundary-scan debugging. The 10-bit ADC with 8 multiplexed channels supports sensor acquisition, while SPI, USART, and TWI (I2C) interfaces cover most communication needs.
The AVR Harvard architecture fetches instructions and data over separate buses, enabling most instructions to complete in one 62.5 ns cycle at 16 MHz. Nested interrupt vectors, a two-cycle hardware multiplier, and sleep modes down to microamp-level idle currents round out the power-performance profile.
Typical applications include industrial control panels, building automation and HVAC controllers, consumer appliances with LCD segments, and data-acquisition nodes using the integrated 10-bit ADC.
Design tip: run the core at 5V when you need the full 16 MHz rating, since flash access time constrains low-voltage operation to lower clock speeds; decouple VCC with 0.1 uF per supply pin.
This page adds distributor pricing tiers, same-package drop-in alternatives, and practical design notes not found in the manufacturer datasheet alone.
Drop-in alternatives for ATMEGA645-16AI — 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 ATMEGA645-16AI (same form factor and footprint) — differing in Operating Temperature, Package, Core Architecture, EEPROM, In-System Programming.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
ATMEGA6450-16AU
✅ Drop-In ⚠️ 参数待验证📋 Reference alternative (not in catalog)
ATMEGA645-16AU
✅ Drop-In ⚠️ 参数待验证📋 Reference alternative (not in catalog)
ATMEGA645A-AU
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$3.95 / Unit
View Datasheet →ATMEGA645P-AU
✅ Drop-In ⚠️ 参数待验证📋 Reference alternative (not in catalog)
ATMEGA6450V-8AU
✅ Drop-In✓ In Stock
$2.31 / Unit
View Datasheet →ATMEGA325-16AU
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$2.4 / Unit
View Datasheet →ATMEGA645-16AI Maximum Ratings & Electrical Characteristics
| Core Architecture | 8-bit AVR RISC |
| Flash Program Memory | 64 KB (32K x 16) ISP |
| SRAM | 4 KB |
| EEPROM | 2 KB |
| Maximum Clock Frequency | 16 MHz |
| Throughput | 16 MIPS at 16 MHz |
| Operating Voltage Range | 2.7 V to 5.5 V |
| ADC | 8-channel, 10-bit |
| Programmable I/O | 68 (device), 54 available on 64-TQFP |
| JTAG Interface | Yes (on-chip debugging and boundary scan) |
| Instruction Set | 130 instructions, mostly single-cycle |
| Operating Temperature | -40C to +85C (industrial, I grade) |
| Package | 64-TQFP (14x14 mm) |
| Mounting Type | Surface Mount |
| Interfaces | USART, SPI, TWI (I2C) |
| ISP Capability | In-System Programmable Flash |
| RoHS Status | Compliant |
ATMEGA645-16AI 64-tqfp (14x14 mm) Pin Configuration Guide
Pin configuration for ATMEGA645-16AI (64-tqfp (14x14 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 ATMEGA645-16AI.
Refer to the datasheet for full pin configuration.
Typical Applications
ATMEGA645-16AI is suitable for 6 applications: Industrial Control Panels, Building Automation and HVAC Controllers, Appliance and Consumer Equipment Control, Data Acquisition and Sensor Nodes, Embedded Networking and Gateways, Instrumentation and Test Fixtures.
Industrial Control Panels
The ATMEGA645-16AI fits industrial control panels because its -40C to +85C industrial temperature grade, 2.7V-5.5V tolerance, and JTAG-based debugging survive the electrical noise and thermal swings of factory cabinets. The 64KB ISP Flash holds large ladder-logic interpreters or Modbus stacks, while the 8-channel 10-bit ADC reads potentiometers, current shunts, and temperature sensors directly. In a typical panel, the MCU scans inputs at 16 MIPS headroom, drives relays via Port pins, and reports over the USART to SCADA. Unlike smaller ATmega parts, the 64-pin footprint leaves ample GPIO for front-panel switches and LED indication without port expanders, reducing BOM count and board layers.
Recommended
Building Automation and HVAC Controllers
HVAC and building-automation controllers benefit from the ATMEGA645-16AI's combination of 64KB Flash for protocol stacks, TWI (I2C) for sensor networks, and the industrial -40C to +85C rating for rooftop and mechanical-room installations. The 8-channel 10-bit ADC samples temperature sensors, humidity transmitters, and pressure inputs, while the USART connects to RS-485 transceivers for BACnet-style multidrop buses. Sleep modes let the controller drop power between 1 Hz sampling ticks, cutting average consumption in battery-backed zones. The 64-TQFP footprint supports the LED-segment and relay driver GPIO counts typical of thermostat and damper boards, all within a single-chip solution that avoids external memory or ADC companion ICs.
Recommended
Appliance and Consumer Equipment Control
White-goods and appliance control boards use the ATMEGA645-16AI where a single chip must drive displays, read touch or potentiometer inputs, and sequence motors. The 64KB Flash accommodates localization strings and multi-mode wash/dry state machines; the 10-bit ADC handles NTC thermistor linearization and over-current detection from shunt resistors. Running from a 5V rail at 16 MHz gives responsive button scanning at 62.5 ns per instruction cycle, and the hardware TWI peripheral reads external EEPROMs or capacitive-touch controllers. The commercial-temp ATMEGA645-16AU variant can be substituted in 0C to +70C consumer enclosures for lower cost, while the industrial-grade AI part covers dishwasher and oven interior sensor nodes.
Recommended
Data Acquisition and Sensor Nodes
Distributed data-acquisition nodes exploit the ATMEGA645-16AI's integrated 8-channel 10-bit ADC and SPI interface to external flash or SD-card media. Each of the eight multiplexed inputs digitizes thermocouple amplifiers, 4-20 mA receiver circuits, or bridge sensors at up to the ADC's full datasheet rate, and the 4KB SRAM buffers sample blocks before SPI burst transfers. The JTAG interface allows in-field firmware updates and boundary-scan verification of assembled boards through the same 64-TQFP header. Because the ADC reference can be switched between AVCC and AREF, ratiometric measurements track supply drift automatically. The industrial temperature grade and 2.7V operation also permit 3.3V sensor front ends with a reduced clock frequency per the voltage-frequency curve.
Recommended
Embedded Networking and Gateways
The ATMEGA645-16AI serves as a protocol-conversion gateway between USART, TWI, and SPI domains in embedded networking equipment. Its 16 MIPS single-cycle RISC core sustains software UART bridges and Modbus RTU framing while the 64KB Flash stores dual firmware banks for failsafe OTA-style updates via ISP. The 68 programmable I/O lines of the device family provide chip-selects for ENC-style Ethernet companion chips or multiple RS-485 transceivers, and hardware SPI runs at half the core clock for fast peripheral transfers. The 64-TQFP 14x14 mm footprint fits standard industrial gateway PCBs with four-layer impedance-controlled routing for the SPI bus, and the JTAG port accelerates bring-up when correlating logic-analyzer captures with firmware execution.
Recommended
Instrumentation and Test Fixtures
Bench instruments and automated test fixtures choose the ATMEGA645-16AI for its JTAG on-chip debugging, 10-bit ADC for measurement channels, and generous 64KB Flash for test scripting. The MCU sequences relay matrices, digitizes DUT responses through the 8-channel ADC, and streams results over USART to a host PC. Because most AVR instructions execute in one cycle, timing-critical stimulus generation achieves deterministic pulse widths at the 62.5 ns granularity of a 16 MHz clock, eliminating bit-bang jitter. The 64-TQFP package's JTAG boundary-scan chain verifies solder joints on the fixture PCB itself, a genuine production benefit. For cost-optimized fixtures with shorter programs, the pin-compatible ATMEGA325-16AU halves Flash while preserving the identical footprint.
Recommended
Recommended Products Summary
Engineering reference data for ATMEGA645-16AI — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ATMEGA6450-16AU | ATMEGA645-16AU | ATMEGA645A-AU | ATMEGA645P-AU | ATMEGA6450V-8AU | ATMEGA325-16AU |
|---|---|---|---|---|---|---|---|
| Package | 64-TQFP (14x14) | 64-TQFP (14x14) - same | 64-TQFP (14x14) - same | 64-TQFP (14x14) - same | 64-TQFP (14x14) - same | 64-TQFP (14x14) - same | 64-TQFP (14x14) - same |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Flash Memory | 64 KB | 64 KB | 64 KB | 64 KB | 64 KB | 64 KB | 32 KB |
| SRAM | 4 KB | 4 KB | 4 KB | 4 KB | 4 KB | 4 KB | 2 KB |
| Maximum Clock Speed | 16 MHz | 16 MHz | 16 MHz | 16 MHz | 20 MHz | 8 MHz | 16 MHz |
| Operating Voltage | 2.7 V to 5.5 V | 4.5 V to 5.5 V | 2.7 V to 5.5 V | 1.8 V to 5.5 V | 1.8 V to 5.5 V | 1.8 V to 5.5 V | 2.7 V to 5.5 V |
| Temperature Grade | -40C to +85C (industrial) | -40C to +85C | 0C to +70C (commercial) | -40C to +85C | -40C to +85C | -40C to +85C | -40C to +85C |
| PicoPower / Low Power Option | No (standard core) | No | No | No | Yes (picoPower) | No (V-grade low voltage) | No |
Key Differentiators
- 64KB Flash in the 64-pin megaAVR footprint (vs ATMEGA325-16AU)
- Industrial temperature rating (vs ATMEGA645-16AU)
- JTAG on-chip debugging and boundary scan (vs ATMEGA325-16AU)
- Honest trade-off: lower voltage flexibility than P/V variants (vs ATMEGA645P-AU)
Design Notes
Decouple every VCC pin of the 64-TQFP with a 0.1 uF ceramic capacitor placed within 3 mm of the pin, plus one 4.7 uF to 10 uF bulk capacitor near the package. Power AVCC separately through an RC or ferrite filter from the digital rail, because AVCC also feeds the 10-bit ADC; ADC noise degrades visibly when AVCC shares digital switching current. Keep the supply within 2.7V-5.5V and remember the datasheet derates the safe clock frequency at lower voltages, so 16 MHz operation requires operation near 5V.
Use an unbroken ground plane under the 64-TQFP and connect all GND pins to it with short vias. Route the JTAG header (TCK, TMS, TDI, TDO) as a short bus with series 33-100 ohm resistors if the debugger cable is longer than 10 cm, to control ringing on TCK edges. Keep XTAL1/XTAL2 crystal traces under 10 mm with guard grounding and load capacitors per the crystal specification. Reserve the RESET pin pull-up (10 k-ohm) and pad for an ISP header so field firmware updates remain possible without JTAG.
Do not assume the 16 MHz rating applies at 3.3V: flash write and execution timing require reduced clock frequency at low supply voltage, per the frequency-versus-voltage curve in the manufacturer datasheet. Second, the ATMEGA645-16AI differs from the commercial ATMEGA645-16AU only in temperature grade, but substituting the commercial part in outdoor or cabinet designs risks failure above +70C. Finally, if migrating to the ATMEGA645P picoPower variant, re-verify ADC calibration and sleep-mode current since peripherals were re-characterized.
Group SPI, TWI, and USART routing away from the ADC input traces on ports used for analog sensing. For the 10-bit ADC, source impedance above 10 k-ohm increases sample-and-hold acquisition error; buffer high-impedance sensors with an op-amp or lengthen the ADC sampling time by reducing the ADC prescaler clock per the datasheet prescaler table. Keep series termination on clock lines leaving the board to limit emissions from the 16 MHz system clock.
Compliance Information
RoHS compliance per standard Microchip megaAVR product classification; specific REACH, halogen-free, and conflict-minerals statements should be confirmed from the Microchip product page environmental documents.
