ATMEGA645V-8AI - 64KB AVR MCU, 8MHz, TQFP-64 | Microchip
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ATMEGA645V-8AI Overview
An AVR ATmega microcontroller is an 8-bit reduced-instruction-set (RISC) MCU that executes most of its instructions in a single clock cycle, positioning it in the embedded microcontroller hierarchy above simple 4-bit controllers and below 32-bit ARM-class devices. The ATmega645V belongs to the megaAVR family and integrates program memory, data memory, peripherals, and CPU on one die, making it a complete embedded processing solution for standalone control tasks.
Key features include the advanced AVR RISC architecture with 130 powerful instructions, 64KB (32K x 16 organization) ISP Flash with Read-While-Write capability, 2KB EEPROM for non-volatile parameter storage, 4KB internal SRAM, and an 8-channel 10-bit ADC. A JTAG interface provides on-chip debugging and Boundary-scan capability, while three flexible Timer/Counters support PWM and event timing. The V-grade speed/voltage class permits operation from 2.7V to 5.5V, allowing use on 3.3V or 5V rails.
Architecturally, the device pairs a fast-access register file of 32 general-purpose working registers with single-cycle execution, achieving approximately 8 MIPS throughput at the 8 MHz maximum frequency. In-System Programmability permits firmware updates on the assembled board through SPI or JTAG.
Typical applications include industrial control panels, sensor data loggers, metering front ends leveraging the 10-bit ADC, and legacy embedded systems requiring 5V-tolerant I/O with ample Flash for protocol stacks or user interfaces.
Design consideration: the 8 MHz ceiling means timing-critical loops must be budgeted accordingly; if 16 MHz operation or a wider 4.5V-5.5V-only supply is acceptable, the ATMEGA645-16AI variant provides identical pinout at double throughput.
This page synthesizes verified distributor data, drop-in same-family alternatives, and practical design notes not consolidated in the manufacturer datasheet.
Drop-in alternatives for ATMEGA645V-8AI — 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 ATMEGA645V-8AI (same form factor and footprint) — differing in Package, Operating Temperature, RoHS Status, Throughput, Program Memory Size.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
ATMEGA645V-8AU
✅ Drop-In📋 Reference alternative (not in catalog)
ATMEGA645A-AUR
✅ Drop-In✓ In Stock
$4.68 / Unit
View Datasheet →ATMEGA645-16AI
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$6.45 / Unit
View Datasheet →ATMEGA645-16AU
✅ Drop-In ⚠️ 参数待验证📋 Reference alternative (not in catalog)
ATMEGA64-16AU
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$7.23 / Unit
View Datasheet →ATMEGA645V-8AI Maximum Ratings & Electrical Characteristics
| Core Architecture | 8-bit AVR RISC |
| Program Memory Size | 64 KB (32K x 16) ISP Flash |
| SRAM Size | 4 KB |
| EEPROM Size | 2 KB |
| Maximum Clock Frequency | 8 MHz |
| Operating Voltage Range | 2.7 V to 5.5 V |
| Instructions | 130 (most single-cycle) |
| Throughput | up to 8 MIPS at 8 MHz |
| General Purpose I/O | 54 I/O lines (64-pin package) |
| ADC | 8-channel, 10-bit |
| Timers/Counters | 3 flexible Timer/Counters |
| Debug Interface | JTAG (on-chip debug, Boundary-scan, programming) |
| Operating Temperature | -40C to +85C (industrial, I suffix) |
| Package | 64-TQFP (14 x 14 mm) |
| Mounting Type | Surface Mount |
| In-System Programming | Yes (ISP Flash, Read-While-Write) |
ATMEGA645V-8AI 64-tqfp (14 x 14 mm) Pin Configuration Guide
Pin configuration for ATMEGA645V-8AI (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 ATMEGA645V-8AI.
Refer to the datasheet for full pin configuration.
Typical Applications
ATMEGA645V-8AI is suitable for 6 applications: Industrial Control Panels, Battery-Powered Data Loggers, Metering and Analog Front Ends, Human-Machine Interfaces and Displays, Legacy System Maintenance and BOM Continuity, Sensor Nodes and IoT Edge Devices.
Industrial Control Panels
The ATMEGA645V-8AI fits industrial panel controllers because its 54 GPIO lines, three Timer/Counters, and industrial -40C to +85C temperature rating cover the switch, relay, and timing needs of machine front-ends without external I/O expanders. Its 2.7V-5.5V tolerance rides out noisy 5V industrial rails, and the 64KB ISP Flash accommodates protocol handling, state machines, and OTA-style bootloader code. A JTAG port enables Boundary-scan production testing of assembled boards, a practical benefit for panel-level QA. Placed as the master MCU driving shift registers and reading the 10-bit ADC for potentiometer or sensor feedback, it executes deterministic single-cycle instructions at up to 8 MIPS; the trade-off versus a 16 MHz sibling is half the throughput, acceptable for most panel logic but verify loop timing on computationally heavy PID code.
Recommended
Battery-Powered Data Loggers
For battery-fed loggers, the ATMEGA645V-8AI's low-voltage speed grade is decisive: it runs directly from a 2.7V-5.5V rail at a full 8 MHz, so a single 3V lithium cell with a small LDO suffices, with no boost converter. The 2KB EEPROM stores calibration constants and rolling log indices across power cycles, while 64KB Flash holds logging firmware plus a bootloader for field updates via its In-System Programming capability. The 8-channel 10-bit ADC samples multiple analog sensors (temperature, pressure, current shunt) without an external converter. The engineering trade-off is power: as a mature megaAVR part it draws more quiescent current than modern picoPower AVRs, so designs should exploit sleep modes aggressively, gate the ADC between conversions, and size the battery from the datasheet power tables at the exact 3.3V operating point rather than from typical active-current figures alone.
Recommended
Metering and Analog Front Ends
The 8-channel, 10-bit ADC of the ATMEGA645V-8AI makes it a compact single-chip metering front end for energy meters, water/gas instruments, and process transducers. Eight analog inputs allow multi-phase or multi-channel measurement in one device, and the integrated programmable-gain-capable ADC with internal reference paths reduces bill-of-materials compared with a separate ADC. The 2KB EEPROM keeps per-device calibration coefficients through power loss, which is mandatory in revenue metering. Operating from 2.7V-5.5V supports legacy 5V meter rails common in industrial installations. Use an averaged/oversampled conversion scheme to push effective resolution beyond 10 bits at the cost of sample rate, and reserve the JTAG-enabled ADC pins (PF4-PF7) carefully: enabling JTAG removes four analog channels, so disable the JTAGEN fuse in production hardware unless Boundary-scan test coverage is required.
Recommended
Human-Machine Interfaces and Displays
With 54 GPIO and 64KB Flash, the ATMEGA645V-8AI drives segment LCDs via external drivers, LED matrices, or character displays while simultaneously scanning keypads, all from one chip. The generous Flash budget accommodates font tables, localized string sets, and menu frameworks alongside the control firmware, while 4KB SRAM buffers display frames. Single-cycle execution keeps scan and refresh interrupt jitter low at 8 MHz, which matters for flicker-free multiplexed LED driving. The wide 2.7V-5.5V supply matches both 3.3V and 5V display logic families, though level-shifting is needed when mixing rails. Designers should budget Timer/Counter resources: with three timers total, one typically drives the display multiplex, one handles keypad debouncing, and one remains for application timing; if the interface also needs advanced PWM backlighting, verify timer allocation early in the schematic phase to avoid conflicts.
Recommended
Legacy System Maintenance and BOM Continuity
A significant ongoing use of the ATMEGA645V-8AI is sustaining legacy ATmega-based products whose firmware depends on the mega645 memory map and peripheral set. Because the die, 64-TQFP footprint, and ISP Flash programming interface are unchanged across the ATmega645 family (V-8AI, V-8AU, 16AI, 16AU, A-series), maintenance engineers can qualify a second source within the family without PCB respin or firmware recompilation risk. The JTAG interface permits on-chip debugging of inherited code even without original source documentation, and Boundary-scan supports board-level retest of repaired units. For end-of-life risk management, dual-source between the V-grade part (3.3V-capable legacy builds) and the 16 MHz A-series (5V builds), matching the exact temperature suffix (I for -40C to +85C) of the original bill of materials to preserve environmental qualification of the finished assembly.
Recommended
Sensor Nodes and IoT Edge Devices
For wired sensor nodes on industrial buses, the ATMEGA645V-8AI offers an economical 8-bit edge controller: its 64KB Flash holds sensor drivers plus a communication stack, 4KB SRAM buffers packet payloads, and the 10-bit ADC digitizes local analog sensors directly. Single-cycle RISC execution provides deterministic response to sensor interrupts at 8 MHz, and In-System Programming supports fleet firmware updates over the bus via a bootloader. The 2.7V-5.5V range suits bus-powered or battery nodes on 3.3V logic. As an 8-bit MCU without integrated radio, wireless connectivity requires an external module over UART/SPI, which adds BOM cost but keeps the certification burden on the module. For computation-heavy edge analytics, the 4KB SRAM is the binding constraint; partition buffers carefully or move feature extraction to the hub rather than the node.
Recommended
Recommended Products Summary
Engineering reference data for ATMEGA645V-8AI — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ATMEGA645V-8AU | ATMEGA645A-AUR | ATMEGA645-16AI | ATMEGA64-16AU |
|---|---|---|---|---|---|
| Package | 64-TQFP (14 x 14 mm) | 64-TQFP - same | 64-TQFP - same | 64-TQFP - same | 64-TQFP - same |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Program Flash | 64 KB | 64 KB | 64 KB | 64 KB | 64 KB |
| SRAM | 4 KB | 4 KB | 4 KB | 4 KB | 4 KB |
| Max Clock Frequency | 8 MHz | 8 MHz | 16 MHz | 16 MHz | 16 MHz |
| Operating Voltage | 2.7 V to 5.5 V | 2.7 V to 5.5 V | 4.5 V to 5.5 V | 4.5 V to 5.5 V | 4.5 V to 5.5 V |
| Peripheral Set | 8-ch 10-bit ADC, 3 timers, JTAG, USI-family serial | Identical to this product | Identical to this product (A-refresh) | Identical to this product | 2x UART, different timer configuration - firmware port needed |
Key Differentiators
- Widest supply range in the ATmega645 family (vs ATMEGA645-16AI)
- Modern A-series process option without respin (vs ATMEGA645A-AUR)
- Direct 645-family firmware compatibility (vs ATMEGA64-16AU)
Design Notes
JTAG pin sharing is the most common ATmega645 design pitfall: the TCK/TMS/TDO/TDI signals are multiplexed with ADC4-ADC7 on Port F (pins PF4-PF7). If the JTAGEN fuse is programmed (default on fresh parts), those four ADC channels are unavailable to the application. Decide at design time whether Boundary-scan/debug access or full 8-channel analog coverage is required; for production boards needing all eight ADC inputs, clear JTAGEN via ISP programmer before relying on ADC4-ADC7, and remember that the change only takes effect after a power cycle.
The V speed grade (2.7V-5.5V, 8 MHz) exists precisely because maximum safe frequency falls with supply voltage on the megaAVR process. Never clock this part above 8 MHz even at 5V, where the 16 MHz grades are the correct choice. Conversely, at 3.3V the 16 MHz variants are out of specification. For battery designs, derate conservatively: estimate worst-case active current from the datasheet DC characteristics at your minimum battery voltage, add per-peripheral loads (ADC reference, timer outputs), and size decoupling (100 nF ceramic per VCC pin plus bulk) to handle ADC conversion transient currents.
The 64-TQFP (14 x 14 mm) has 0.5 mm pin pitch; specify a solder-mask-defined or non-solder-mask-defined pad per your assembler's capability and use 1:1 stencil apertures with 0.1 mm reduction to prevent bridging. Place 100 nF decoupling capacitors within 2-3 mm of each VCC pin with a solid ground return, and tie AVCC to VCC through an LC filter (ferrite plus 100 nF/10 uF) when using the ADC to keep digital noise out of conversions. Route the crystal as short as possible with guard ground, and provide a 6-pin ISP header plus optional 2x5 JTAG header (2.54 mm or 1.27 mm) for in-system updates and debug.
Compliance Information
RoHS/REACH status was not stated in the verified web data for the AI suffix (the GREEN designation was only confirmed for the AU suffix on FindIC). Verify current compliance certificates on the Microchip product page before procurement.
