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Home Products Integrated Circuits (ICs)Embedded - Microcontrollers~~ATMEGA168P-20MQR~~

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ATMEGA168P-20MQR - Atmel

Name: Atmel ATMEGA168P-20MQR
Brand: Atmel
SKU: ATMEGA168P-20MQR
Availability: InStock
Rating: 5 (8 reviews)

Manufacturer Part Number: ATMEGA168P-20MQR

Manufacturer: Atmel

Allelco Part Number: 98D-ATMEGA168P-20MQR

Warranty: 1 Year Allelco Warranty - Find out more

Stock Status:: 10,399 pcs available, New & Original

Parts Description: IC MCU 8BIT 16KB FLASH 32VQFN

Package: 32-VQFN (5x5)

Data sheet: -

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In stock: 10399

Specifications

ATMEGA168P-20MQR Tech Specifications
Atmel - ATMEGA168P-20MQR technical specifications, attributes, parameters and parts with similar specifications to Atmel - ATMEGA168P-20MQR

Product Attribute	Attribute Value
Manufacturer	Atmel
Voltage - Supply (Vcc/Vdd)	2.7V ~ 5.5V
Supplier Device Package	32-VQFN (5x5)
Speed	20MHz
Series	AVR® ATmega
RAM Size	1K x 8
Program Memory Type	FLASH
Program Memory Size	16KB (8K x 16)
Peripherals	Brown-out Detect/Reset, POR, PWM, WDT
Package / Case	32-VFQFN Exposed Pad
Package	Bulk

Product Attribute	Attribute Value
Oscillator Type	Internal
Operating Temperature	-40°C ~ 105°C (TA)
Number of I/O	23
Mounting Type	Surface Mount
EEPROM Size	512 x 8
Data Converters	A/D 8x10b
Core Size	8-Bit
Core Processor	AVR
Connectivity	I²C, SPI, UART/USART
Base Product Number	ATMEGA168

Environmental & Export Classifications

ATTRIBUTE	DESCRIPTION
ECCN	EAR99
HTSUS	8542.31.0001

Frequently Asked Questions(FAQ)

What are the key performance trade-offs when selecting between internal and external clock sources for the ATMEGA168P-20MQR in a battery-powered embedded application?: The ATMEGA168P-20MQR supports an internal calibrated RC oscillator that operates at 20MHz with ±10% accuracy, making it suitable for low-power designs where precision timing is not critical. However, this internal oscillator may drift with temperature and voltage variations, potentially affecting communication protocols like UART or I²C. In contrast, using an external crystal or resonator provides higher stability (±20–100 ppm), which is essential for reliable serial communication over longer durations or across environmental changes. For applications requiring accurate baud rates or synchronization, an external clock source is preferable despite the increased component count and power consumption from driving the external resonator.

How does the ATMEGA168P-20MQR handle brownout detection during voltage sags, and what design considerations should be made to ensure system reliability under power fluctuations?: The ATMEGA168P-20MQR includes a programmable Brown-out Detection (BOD) feature that monitors VCC and resets the microcontroller if the supply voltage drops below a user-defined threshold—typically selectable in steps around 2.7V, 4.3V, or 4.0V depending on configuration. During a brownout event, the BOD triggers a hardware reset, preventing erratic behavior from undervoltage conditions. Designers must consider the BOD level relative to their system’s minimum operating voltage (2.7V to 5.5V). Setting the BOD too high risks premature resets during brief dips, while setting it too low may allow operation outside safe logic levels. Proper decoupling capacitance and transient protection circuits should also complement BOD functionality to enhance robustness.

Can the ATMEGA168P-20MQR support real-time clock (RTC) functionality without an external timer, and what limitations apply when relying solely on its internal peripherals?: No, the ATMEGA168P-20MQR does not include a dedicated RTC module; however, real-time tracking can be implemented using Timer/Counter2 in asynchronous mode with an external 32.768 kHz crystal connected to the TOSC1/TOSC2 pins. This allows the watchdog timer (WDT) or a software loop to measure elapsed time with reasonable accuracy. The internal oscillator cannot maintain long-term timekeeping due to drift, so external crystals are required for precision. Additionally, powering the MCU in idle or power-save modes reduces current draw but increases wake-up latency, which must be accounted for in time-sensitive applications.

How does the 32-VQFN (5x5) package of the ATMEGA168P-20MQR impact thermal management and layout complexity compared to larger QFP alternatives?: The compact 32-VQFN (5x5 mm) package offers high pin density and space efficiency, ideal for portable or densely populated PCBs. However, its exposed thermal pad enhances heat dissipation but requires careful PCB layout: the pad must be soldered directly to a solid ground plane with multiple vias to avoid thermal resistance buildup. Without proper thermal relief, localized heating near the IC could affect reliability, especially during sustained operation at 20MHz. Compared to 32-pin QFPs, the VQFN reduces board area by up to 40%, but designers must account for stricter soldering profiles (e.g., reflow oven control) and potential challenges in manual assembly or rework.

What is the significance of the Moisture Sensitivity Level (MSL) rating of 3 for the ATMEGA168P-20MQR, and how does it influence manufacturing process planning?: With an MSL of 3, the ATMEGA168P-20MQR is classified as moisture-sensitive and requires bake-out before reflow soldering if stored beyond 168 hours above 30°C/60% RH. This precaution prevents popcorning—delamination-induced cracking from trapped moisture expanding during thermal cycling. Manufacturers must track shelf life using FIFO (first-in, first-out) inventory practices and follow J-STD-033 guidelines for handling. Failure to adhere to MSL requirements can lead to field failures even if initial tests pass, particularly in humid environments or high-temperature operations up to 105°C.

In what scenarios would using the ATMEGA168P-20MQR’s internal ADC with 10-bit resolution be insufficient, and what external components might improve measurement accuracy?: While the internal 8-channel, 10-bit ADC provides adequate resolution for many analog sensing tasks (e.g., thermistor readings or battery voltage monitoring), its accuracy is limited by reference voltage stability and input impedance. Without an external precision voltage reference (e.g., ADR391), the ADC may exhibit errors greater than ±2 LSB due to Vcc fluctuations. Additionally, signal conditioning such as op-amp buffers or low-pass filters is often necessary to prevent aliasing and reduce noise. For applications demanding <1% linearity or multi-point calibration, pairing the ATMEGA168P-20MQR with discrete components significantly enhances measurement fidelity beyond what the MCU alone can deliver.

How should interrupt handling be configured to minimize latency when using multiple peripherals like UART and SPI simultaneously on the ATMEGA168P-20MQR?: To optimize interrupt response times, prioritize interrupts based on real-time requirements—assign higher priority to time-critical events such as SPI data reception or UART receive complete. The ATMEGA168P-20MQR uses a fixed-priority vector table where lower-numbered interrupts have precedence. Disable global interrupts briefly during ISR entry/exit to prevent race conditions, and keep ISRs concise to avoid delaying higher-priority tasks. Using the sleep modes (e.g., idle) reduces power but increases wake-up latency; thus, balancing responsiveness and energy efficiency requires careful analysis of task deadlines versus power budget constraints.

What are the implications of operating the ATMEGA168P-20MQR at the upper end of its temperature range (-40°C to +105°C) on oscillator stability and flash memory endurance?: At elevated temperatures approaching 105°C, the internal RC oscillator of the ATMEGA168P-20MQR may experience frequency drift beyond typical specifications, impacting timing-sensitive operations. Flash memory retention decreases exponentially with temperature, reducing expected data lifetime from ~10 years at 25°C to possibly months at 105°C without periodic refresh cycles. Additionally, leakage currents increase, raising quiescent power consumption slightly. For mission-critical systems, derating the operating temperature or adding external compensation (e.g., temperature-stabilized oscillators) becomes necessary to maintain reliability over the full industrial range.

How does the choice between internal pull-ups versus external resistors affect noise immunity and power consumption in digital input lines driven by the ATMEGA168P-20MQR?: Internal pull-up resistors on the ATMEGA168P-20MQR are typically 20kΩ to 50kΩ and consume negligible current when active, making them convenient for open-collector or high-impedance sensor interfaces. However, their weak drive strength increases susceptibility to electromagnetic interference (EMI) and capacitive coupling, especially in long traces or noisy environments. External pull-ups (e.g., 1kΩ to 10kΩ) offer stronger assertion levels and faster rise times but draw more current (e.g., 3.3V / 1kΩ = 3.3mA), increasing standby power. The optimal selection depends on trace length, ambient noise, and battery life targets, requiring trade-offs between signal integrity and energy efficiency.

Can the ATMEGA168P-20MQR run code directly from EEPROM, and what are the practical limitations of this approach compared to executing from flash?: No, the ATMEGA168P-20MQR executes instructions exclusively from its 16KB flash memory; the 512-byte EEPROM is strictly for non-volatile data storage. Attempting to execute code from EEPROM will result in undefined behavior or hard faults because the CPU fetches machine instructions only from flash. While EEPROM offers faster write endurance (up to 100,000 cycles vs. 10,000 for flash) and byte-level updates, it lacks the instruction set compatibility required for direct program execution. Thus, developers must always load firmware into flash and use EEPROM sparingly for configuration parameters or logging data.

What considerations apply when cascading multiple SPI devices with the ATMEGA168P-20MQR, particularly regarding clock polarity and chip select management?: When connecting multiple SPI slaves, the ATMEGA168P-20MQR’s SPI master must match each device’s CPOL and CPH settings via the SPCR register. Mismatched configurations cause data misalignment or failed transfers. Each slave requires a separate SS (Slave Select) line driven low during transactions, with strict adherence to setup/hold times around SCK edges. Since the ATMEGA168P-20MQR has only one hardware SS pin, software-controlled GPIOs must manage additional CS lines. Proper isolation using tri-state buffers or level shifters is also recommended if interfacing mixed-voltage slaves within the 2.7V–5.5V range.

How does the ATMEGA168P-20MQR’s single-supply operation (2.7V–5.5V) simplify power architecture compared to dual-voltage MCUs, and what constraints arise from this design?: Operating across a wide supply range eliminates the need for separate regulators for logic and peripherals, reducing BOM cost and board complexity. The ATMEGA168P-20MQR can interface with 5V sensors or 3.3V subsystems without level shifting, provided all inputs stay within VIH/VIL thresholds for the chosen Vcc. However, at lower voltages (e.g., 2.7V), drive strength decreases, potentially causing signal degradation on long traces or capacitive loads. Additionally, analog performance (ADC, comparators) degrades near the minimum supply, necessitating careful calibration or voltage margining in low-power designs.

What role does Watchdog Timer (WDT) play in enhancing system resilience for the ATMEGA168P-20MQR, and how should it be configured to balance fault recovery and false triggers?: The WDT provides automatic system reset if the firmware hangs or enters an infinite loop, acting as a last-resort safety net. Configurable timeout periods range from 16ms to 8s, allowing tuning based on application responsiveness needs. Shorter intervals detect soft locks quickly but risk nuisance resets from delayed tasks; longer intervals conserve power but delay recovery from deadlocks. Best practice involves enabling WDT early in initialization and periodically clearing it (“petting” the dog) in normal operation. Pairing WDT with BOD and software heartbeat monitoring creates a robust failure containment strategy without overburdening the main code path.

Is it possible to reprogram the ATMEGA168P-20MQR while mounted on the final PCB, and what interface options support in-system programming (ISP)?: Yes, the ATMEGA168P-20MQR supports in-system programming via the standard SPI-compatible ISP header (MOSI, MISO, SCK, RESET, Vcc, GND). As long as these pins remain accessible and unconflicted by other peripherals, the device can be reprogrammed using tools like AVRISP mkII or USBasp without desoldering. However, during programming, the RESET pin must be pulled low to enter programming mode, so any downstream circuitry (e.g., reset controllers) must allow this interaction. Bootloader-based approaches further simplify field updates but require allocating flash space and implementing communication protocols like UART or I²C.

How does the absence of a built-in CAN transceiver affect integration of automotive or industrial communication stacks using the ATMEGA168P-20MQR?: The ATMEGA168P-20MQR lacks native CAN controller functionality, so implementing CAN bus communication demands either an external CAN controller chip (e.g., MCP2515) with SPI interface or software-based bit-banging with significant CPU overhead. Real-time CAN arbitration and error handling become challenging at 20MHz, potentially limiting throughput to non-critical messaging. For industrial applications requiring deterministic communication, pairing the MCU with a dedicated CAN transceiver (e.g., TJA1050) adds complexity but enables compliance with protocols like CANopen or DeviceNet, trading simplicity for functional capability.

What factors determine whether the ATMEGA168P-20MQR meets EMC requirements in consumer electronics, and how can emissions be mitigated during layout?: The ATMEGA168P-20MQR itself contributes minimal radiated emissions due to its moderate-speed operation (20MHz max), but poor PCB layout amplifies EMI. Key mitigation strategies include minimizing loop areas for high-current paths, placing decoupling capacitors within 2mm of Vcc/GND pins, using ground planes to reduce impedance, and avoiding parallel routing of clock and data lines. Clock harmonics above 20MHz (from fast edges) can radiate unless filtered. Shielding sensitive analog sections and ensuring proper return paths help meet FCC Part 15 or EN 55022 standards, though full certification often requires external filtering and enclosure design beyond the MCU alone.

Parts with Similar Specifications

The three parts on the right have similar specifications to Atmel ATMEGA168P-20MQR

Product Attribute
Part Number	ATMEGA168P-20MQR	ATMEGA168P-20MQ	ATMEGA168P-20MUR	ATMEGA168P-20MQ
Manufacturer	Microchip Technology	Microchip Technology	Atmel	Atmel
Voltage - Supply (Vcc/Vdd)	-	-	-	-
Package / Case	-	196-LFBGA	16-DIP (0.300', 7.62mm)	64-VFQFN Exposed Pad
Series	-	-	-	-
Core Size	-	-	-	-
Supplier Device Package	-	196-NFBGA (12x12)	16-PDIP	64-VQFN (9x9)
Data Converters	-	-	-	-
Operating Temperature	-	-40°C ~ 85°C	0°C ~ 70°C	-40°C ~ 85°C
EEPROM Size	-	-	-	-
Program Memory Size	-	-	-	-
Base Product Number	-	DAC34H84	MAX500	ADS62P42
Peripherals	-	-	-	-
Oscillator Type	-	-	-	-
Speed	-	-	-	-
Package	-	Tape & Reel (TR)	Tube	Tape & Reel (TR)
RAM Size	-	-	-	-
Program Memory Type	-	-	-	-
Number of I/O	-	-	-	-
Mounting Type	-	Surface Mount	Through Hole	Surface Mount
Core Processor	-	-	-	-
Connectivity	-	-	-	-

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Customer Reviews

Evaluation: 10 Articles

Dani***alkerTech

Jun 1, 2026

Product works, but setup took more effort than expected. Once configured the MCU ran reliably, although documentation support felt older compared with newer platforms. Fine for maintenance projects.
Yuki***aka88

May 26, 2026

信号通信プロジェクトでこのRS-485トランシーバーを使用しました。設置は簡単で、長距離ケーブルでも通信は安定していました。消費電力も、以前使用していたものより低くなっています。
Stev***aker

May 20, 2026

Solid diode for power rectification. Works well in switching circuits.
Bran***Lewis

May 11, 2026

Compact FPGA with good performance. Suitable for basic signal processing tasks.
Oliv***arris

May 7, 2026

Reliable I/O expander. Works well in embedded control applications.
Jess***Jones

Apr 17, 2026

It offers good value for the price, and the specifications match the description. I’ve been using it for two days with no issues, and I’ll definitely buy it again if I need it in the future.
Mich***Smith

Apr 17, 2026

Shipping was on time, the component pins are neatly aligned, and I tested 10 of them with a multimeter—all readings were within the specified range. Highly recommended.
Aman***arris

Apr 3, 2026

It was great—the entire process, from placing the order to receiving the package, went very smoothly. The components were consistent, the price was fair, and I had a very pleasant shopping experience.
Mike***nch

Apr 3, 2026

Better than expected! The resistance and capacitance readings were spot-on, and it passed the test on the first try. The service was reliable, and the packaging was thoughtful—I highly recommend it.
Daic***K.

Mar 23, 2026

Very good. No issue after long time testing.

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