ATMEGA644P-20MQR - 8-Bit AVR MCU 20MHz 64KB | Microchip
MPN: ATMEGA644P-20MQR ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $6.36 | $6.36 |
| 10 | $5.9 | $59.00 |
| 100 | $5.3 | $530.00 |
| 500 | $4.8 | $2,400.00 |
| 1,000 | $4.3 | $4,300.00 |
ATMEGA644P-20MQR Overview
An 8-bit AVR microcontroller is a single-chip computer that combines an enhanced RISC CPU, program and data memory, and a rich set of peripherals on one die. Within the broader product hierarchy, it belongs to the ATmega family of AVR MCUs, which in turn sit under the microcontroller and embedded-processor categories of the semiconductor taxonomy.
Key features include 131 powerful instructions with mostly single-clock-cycle execution, achieving close to 1 MIPS per MHz throughput. The 'P' variant adds a second USART, giving two full-duplex serial ports, plus SPI, two-wire interface (TWI/I2C), a 10-bit 8-channel ADC, two 8-bit and one 16-bit timers, and JTAG for on-chip debugging and boundary scan. picoPower technology supports low-power sleep modes for battery-sensitive designs.
Architecturally, the device executes powerful instructions in a single clock cycle, letting system designers optimize the trade-off between processing speed and power consumption. In-system programmable (ISP) Flash via In-Circuit Serial Programming (ICSP) simplifies field updates, and debugging is supported through the MPLAB Snap and compatible AVR tools using two I/O pins plus reset.
Typical applications include industrial automation controllers, dual-channel serial communication gateways using the twin USARTs, and precision analog sensor acquisition via the 8-channel 10-bit ADC.
Design consideration: full 20 MHz operation requires a supply of 4.5V to 5.5V; lower-voltage operation derates the maximum safe clock frequency, so verify the frequency-versus-voltage curve before clocking down.
This page synthesizes distributor pricing, drop-in alternatives, pinout data, and practical design notes not found in the manufacturer datasheet.
Drop-in alternatives for ATMEGA644P-20MQR — 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 ATMEGA644P-20MQR (same form factor and footprint) — differing in SRAM, Package, Debug Interface, Throughput, EEPROM.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
ATMEGA644P-20MQ
✅ Drop-In✓ In Stock
$2.48 / Unit
View Datasheet →ATMEGA644PA-MUR
✅ Drop-In📋 Reference alternative (not in catalog)
ATMEGA644PA-AU
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$2.49 / Unit
View Datasheet →ATMEGA64-16MI
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$4.48 / Unit
View Datasheet →ATMEGA644-20AU
✅ Drop-In✓ In Stock
$4.96 / Unit
View Datasheet →ATMEGA644P-20MQR Maximum Ratings & Electrical Characteristics
| Core Processor | AVR 8-bit RISC |
| Core Size | 8-bit |
| Speed (Max Clock) | 20 MHz |
| Flash Program Memory | 64 KB (32K x 16) |
| SRAM | 4 KB (4K x 8) |
| EEPROM | 2 KB |
| Number of I/O | 32 |
| Supply Voltage (VCC) | 4.5 V to 5.5 V (at 20 MHz) |
| Oscillator Type | Internal |
| USART Count | 2 (P variant dual USART) |
| Timers | Two 8-bit, one 16-bit |
| ADC | 8-channel, 10-bit |
| Communication Interfaces | USART x2, SPI, TWI (I2C) |
| Debug Interface | JTAG (on-chip debug, boundary scan) |
| Instruction Set | 131 instructions, mostly single-cycle |
| Low Power Technology | picoPower |
| Operating Temperature | -40C to +105C (extended, M grade) |
| Package / Case | 44-VQFN (7x7 mm) exposed pad (MLF) |
| Mounting Type | Surface Mount |
| Packaging | Tape & Reel (TR) |
| RoHS / Green Status | GREEN, RoHS compliant |
ATMEGA644P-20MQR Pin Configuration
| Pin 1 | PA4 (ADC4) — Port A bit 4 / ADC input 4 |
| Pin 2 | PA5 (ADC5) — Port A bit 5 / ADC input 5 |
| Pin 3 | PA6 (ADC6) — Port A bit 6 / ADC input 6 |
| Pin 7 | AREF — Analog reference for ADC |
| Pin 8 | PA3 (ADC3) — Port A bit 3 / ADC input 3 |
| Pin 9 | PA2 (ADC2) — Port A bit 2 / ADC input 2 |
| Pin 10 | PA1 (ADC1) — Port A bit 1 / ADC input 1 |
| Pin 11 | PA0 (ADC0) — Port A bit 0 / ADC input 0 |
| Pin 14 | PB0 (XCK0/T0) — Port B bit 0, USART0 external clock / Timer0 |
| Pin 15 | PB1 (T1/CLKO) — Port B bit 1, Timer1 / clock output |
| Pin 16 | PB2 (AIN0/INT2) — Port B bit 2, analog comparator / external interrupt 2 |
| Pin 17 | PB3 (AIN1/OC0A) — Port B bit 3, comparator / PWM output 0A |
| Pin 18 | PB4 (SS) — Port B bit 4, SPI slave select |
| Pin 19 | PB5 (MOSI) — Port B bit 5, SPI master output |
| Pin 20 | PB6 (MISO) — Port B bit 6, SPI master input |
| Pin 21 | PB7 (SCK) — Port B bit 7, SPI clock |
| Pin 24 | PC0 (SCL) — Port C bit 0, TWI clock |
| Pin 25 | PC1 (SDA) — Port C bit 1, TWI data |
| Pin 26 | PC2 (TCK) — Port C bit 2, JTAG test clock |
| Pin 27 | PC3 (TMS) — Port C bit 3, JTAG test mode select |
| Pin 28 | PC4 (TDO) — Port C bit 4, JTAG test data out |
| Pin 29 | PC5 (TDI) — Port C bit 5, JTAG test data in |
| Pin 30 | PC6 (TOSC1) — Port C bit 6, timer oscillator input |
| Pin 31 | PC7 (TOSC2) — Port C bit 7, timer oscillator output |
| Pin 34 | PD0 (RXD0) — Port D bit 0, USART0 receive |
| Pin 35 | PD1 (TXD0) — Port D bit 1, USART0 transmit |
| Pin 36 | PD2 (RXD1/INT0) — Port D bit 2, USART1 receive / interrupt 0 |
| Pin 37 | PD3 (TXD1/INT1) — Port D bit 3, USART1 transmit / interrupt 1 |
| Pin 38 | PD4 (XCK1/OC1B) — Port D bit 4, USART1 clock / PWM 1B |
| Pin 39 | PD5 (OC1A) — Port D bit 5, PWM output 1A |
| Pin 40 | PD6 (OC2A/ICP1) — Port D bit 6, PWM 2A / input capture |
| Pin 41 | PD7 (OC0B/RT0) — Port D bit 7, PWM 0B |
| Pin 42 | RESET — Active-low reset input |
| Pin 43 | XTAL1 — External clock / crystal input |
| Pin 44 | XTAL2 — Crystal output |
Typical Applications
ATMEGA644P-20MQR is suitable for 6 applications: Industrial Automation Controllers, Dual-Channel Serial Communication Gateways, Analog Sensor Data Acquisition, Embedded Prototyping and Education Platforms, Appliance and Consumer Control Boards, Motor Control and Actuation Systems.
Industrial Automation Controllers
The ATMEGA644P-20MQR fits industrial control panels and programmable logic nodes because its extended -40C to +105C temperature rating and 4.5V to 5.5V 5V-tolerant supply match harsh factory-floor conditions where standard commercial parts fail. The 64 KB Flash accommodates state-machine and communication firmware with headroom for OTA-style field updates via ICSP, while 32 GPIO lines drive relays, read limit switches, and interface to HMI peripherals. The 8-channel 10-bit ADC digitizes thermistors and 4-20 mA-derived signals at up to 10-bit resolution, and JTAG enables on-chip debugging during commissioning. Placed on a 5V rail with 100 nF decoupling per supply pin, its single-cycle 20 MHz execution handles PID loops and sequential control with deterministic timing.
Recommended
Dual-Channel Serial Communication Gateways
The dual USART of the ATmega644P 'P' variant is the defining feature for protocol gateways: one USART bridges an RS-485 Modbus network while the second services RS-232 diagnostics or a cellular module, all without software UART emulation overhead. Running at 20 MHz with single-cycle execution, the core sustains simultaneous baud rates up to 1 Mbps on both ports with error checking via frame and parity flags. The 44-VQFN (7x7 mm) package keeps the gateway PCB compact, and the extended -40C to +105C range suits unenclosed outdoor cabinets. The 4 KB SRAM buffers packet frames, and 2 KB EEPROM stores node addresses and configuration parameters through power cycles. Level shifters or transceivers on the USART pins complete a robust, self-contained bridge design.
Recommended
Analog Sensor Data Acquisition
The integrated 8-channel 10-bit ADC makes the ATMEGA644P-20MQR a compact data-logger front end: up to eight sensor channels (temperature, humidity, pressure bridges, potentiometers) are multiplexed internally at up to 15 kSPS at full resolution. The AREF pin supports external precision references for improved absolute accuracy, and the internal bandgap option suits ratiometric measurements. With picoPower sleep modes, battery-powered loggers sample periodically at microamp-level sleep current, waking via timer interrupt. The 4 KB SRAM stores sample windows before block writes to external Flash over SPI, and 2 KB EEPROM retains calibration coefficients. The 7x7 mm VQFN with exposed pad grounds the analog die attach for low-noise operation, and the extended temperature rating supports outdoor and cold-chain monitoring hardware.
Recommended
Embedded Prototyping and Education Platforms
The ATmega644P is a popular core for teaching and maker platforms (for example, Sanguino-class boards) because the AVR architecture is well documented, the 64 KB Flash removes size pressure during experimentation, and ICSP programming needs only four signal pins. The 32 GPIOs mapped across four 8-bit ports give students immediate access to buttons, LEDs, LCDs, and servo banks, while SPI and TWI host shields and sensors. The internal oscillator allows clock-less bring-up before an external 20 MHz crystal is fitted, and JTAG permits step-level debugging with standard AVR tools on one header. With 1 MIPS per MHz throughput, timing exercises behave predictably. The VQFN-44 package suits both custom two-layer student PCBs and pre-assembled trainer boards.
Recommended
Appliance and Consumer Control Boards
White-goods and appliance control boards benefit from the ATMEGA644P-20MQR's combination of 5V robustness, large 64 KB program space for multi-language UI and fault-logging firmware, and low-cost peripheral integration that eliminates external UART, EEPROM, and ADC chips. The 32 I/O lines drive seven-segment displays, relays, triac triggers, and touch or rotary inputs directly. The 2 KB EEPROM preserves user settings and cycle counters through mains interruptions, and the 10-bit ADC reads NTC thermistors and mains-sense dividers. The extended -40C to +105C rating covers unventilated motor compartments. Because the part is in tape-and-reel packaging, high-volume SMT lines feed it directly into pick-and-place, and the exposed-pad VQFN aids heat spreading within sealed enclosures.
Recommended
Motor Control and Actuation Systems
DC and stepper motor controllers exploit the ATMEGA644P-20MQR's one 16-bit timer (dual-slope PWM for precise speed control) plus two 8-bit timers for auxiliary PWM channels and scheduling. The 20 MHz single-cycle core executes FOC-lite or sensorless algorithms fast enough for small-motor applications, while the ADC samples current shunts and back-EMF. The 32 GPIOs drive gate drivers, H-bridge modules, and quadrature inputs, and external interrupts handle encoder counting. Operating from a 5V rail with the -40C to +105C grade, the controller survives enclosure heat near power stages; the exposed VQFN pad bonds to the PCB ground plane for thermal relief. JTAG on-chip debug lets engineers tune current-loop constants directly on the running motor hardware.
Recommended
Recommended Products Summary
Engineering reference data for ATMEGA644P-20MQR — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ATMEGA644P-20MQ | ATMEGA644PA-MUR | ATMEGA644PA-AU | ATMEGA64-16MI | ATMEGA644-20AU |
|---|---|---|---|---|---|---|
| Package | 44-VQFN (7x7 mm, MLF) exposed pad | 44-VQFN (7x7 mm, MLF) - same | 44-VQFN (7x7 mm, MLF) - same | 44-TQFP (10x10 mm) - different footprint | 44-VQFN (MLF) - same | 44-TQFP (10x10 mm) - different footprint |
| Brand | Microchip Technology (Atmel) | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Max Clock Frequency | 20 MHz | 20 MHz | 20 MHz | 20 MHz | 16 MHz | 20 MHz |
| Flash Program Memory | 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 |
| USART Count | 2 (dual, P variant) | 2 | 2 | 2 | 2 | 1 |
| Operating Temperature | -40C to +105C (extended) | -40C to +105C | -40C to +105C | -40C to +85C | -40C to +105C | -40C to +85C |
Key Differentiators
- Dual USART for two simultaneous serial links (vs ATMEGA644-20AU)
- Extended -40C to +105C temperature grade (vs ATMEGA644PA-AU)
- Official active successor available with same footprint (vs ATMEGA644PA-MUR)
Design Notes
The ATMEGA644P-20MQR requires 4.5V to 5.5V for guaranteed 20 MHz operation; at 3.3V the safe maximum frequency is significantly lower per the frequency-versus-voltage curve in the datasheet. Estimated: a typical load of 32 GPIOs at 20 mA each plus core current of roughly 25 mA can draw over 600 mA, so size the 5V regulator accordingly and place 100 nF ceramic capacitors on every VCC pin with one 10 uF bulk capacitor at the board entry.
The 44-VQFN (MLF) package has an exposed die-attach pad on the underside that must be soldered to a ground-plane keepout array of thermal vias - it is the primary ground connection, not just thermal relief. Use a 3x3 or 4x4 via farm under the pad and a solder-paste stencil with about 50-70% coverage to avoid float during reflow. JTAG (PC2-PC5) and ICSP (PB5-PB7, RESET) should be routed to test points for programming and debug access.
Do not treat the ATmega644P as a long-term sourcing strategy: Microchip designates it a mature product not recommended for new designs, replaced by the ATmega644PA. For new layouts, design directly with ATMEGA644PA-MUR to secure future supply. Also note the second USART (PD2/PD3) exists only on 'P'-suffix parts - firmware written for it will fail silently on standard ATmega644 silicon, so verify the die variant at incoming inspection when dual-sourcing.
Compliance Information
Described as GREEN per Microchip/Atmel product data (FindIC listing), which denotes RoHS-compliant lead-free, halogen-free packaging. REACH and conflict-minerals status not stated in provided data.
