ATMEGA168A-AU - 8-Bit AVR MCU 16KB Flash 20MHz | Microchip
MPN: ATMEGA168A-AU β Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $2.19 | $2.19 |
| 10 | $1.98 | $19.80 |
| 100 | $1.76 | $176.00 |
| 500 | $1.58 | $790.00 |
| 1,000 | $1.42 | $1,420.00 |
ATMEGA168A-AU Overview
An AVR microcontroller is a Harvard-architecture 8-bit RISC device that executes most instructions in a single clock cycle, sitting in the hierarchy of microcontroller -> embedded processor -> integrated circuit -> semiconductor. The ATmega168A family is the second-generation "A" revision of the classic ATmega168, adding improved brown-out detection, a calibrated internal RC oscillator, and enhanced EEPROM endurance while retaining full pin and code compatibility with the original ATmega168 and the picoPower ATmega168P/PA devices.
Key features include 16 KB ISP flash with read-while-write capability, 512 B EEPROM rated for 100,000 write/erase cycles, 1 KB internal SRAM, 23 programmable I/O lines, 32 general-purpose working registers, three flexible timer/counters with compare modes, a serial programmable USART, a byte-oriented Two-Wire serial interface, and an SPI serial port. The device also integrates a 10-bit ADC, a programmable watchdog timer with internal oscillator, and six sleep modes for low-power operation.
The ATmega168A uses Microchip's high-performance, low-power AVR 8-bit RISC architecture with 131 powerful instructions, most executing in a single clock cycle, achieving throughput approaching 1 MIPS per MHz. This allows the system designer to optimize power consumption versus processing speed. The 32-TQFP package measures 7x7 mm with a 0.8 mm pitch, making it suitable for compact surface-mount assemblies.
Typical applications include Arduino-compatible development boards, industrial sensor nodes, battery-powered IoT endpoints, motor control, home automation, and portable instrumentation. The wide 2.7 V to 5.5 V supply range supports both 3.3 V and 5 V logic systems, and the integrated peripherals reduce external component count.
When designing with this device, decouple VCC and AVCC with 100 nF ceramic capacitors placed close to the pins, and connect the AREF pin through a low-pass filter when using the ADC. The RESET pin requires an external pull-up or the internal pull-up must be enabled.
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes not found in the manufacturer datasheet, providing engineers with a single reference for selection, replacement, and layout decisions.
Drop-in alternatives for ATMEGA168A-AU β 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 ATMEGA168A-AU (same form factor and footprint) β differing in Operating Temperature, Timers, Programming, Serial Interfaces, Package.
Quick Comparison Tool β Select alternative parts for side-by-side comparison:
ATMEGA168PA-AU
β Drop-Inπ Reference alternative (not in catalog)
ATMEGA168-20AU
β Drop-Inβ In Stock
$1.82 / Unit
View Datasheet βATMEGA168A-AUR
β Drop-Inβ In Stock
$1.45 / Unit
View Datasheet βATMEGA168PA-AUR
β Drop-Inπ Reference alternative (not in catalog)
ATMEGA328P-AU
β Drop-Inβ In Stock
$1.9 / Unit
View Datasheet βATMEGA88PA-AU
β Drop-Inπ Reference alternative (not in catalog)
ATMEGA168A-AU Maximum Ratings & Electrical Characteristics
| Core Architecture | 8-bit AVR RISC |
| Program Memory Size | 16 KB (8K x 16) Flash |
| Program Memory Type | Flash (ISP, read-while-write) |
| EEPROM Size | 512 B |
| SRAM Size | 1 KB |
| Maximum Clock Frequency | 20 MHz |
| Operating Voltage Range | 2.7 V to 5.5 V |
| Number of I/O Lines | 23 |
| General Purpose Registers | 32 |
| Instruction Set | 131 instructions, most single-cycle |
| Timers/Counters | 3 (two 8-bit, one 16-bit) with compare modes |
| Serial Interfaces | USART, SPI, Two-Wire (I2C) |
| ADC Resolution | 10-bit |
| Package | 32-TQFP (7x7 mm) |
| Mounting Type | Surface Mount |
| Operating Temperature | -40 C to +85 C |
| Sleep Modes | 6 (Idle, ADC Noise Reduction, Power-save, Power-down, Standby, Extended Standby) |
| RoHS Status | Compliant |
| Lifecycle Stage | Active |
ATMEGA168A-AU Pin Configuration
| Pin 1 | PD3 β Port D, bit 3 (also INT1, OC2B) |
| Pin 2 | PD4 β Port D, bit 4 (also T0, XCK) |
| Pin 3 | GND β Ground |
| Pin 4 | VCC β Digital supply voltage |
| Pin 5 | GND β Ground |
| Pin 6 | VCC β Digital supply voltage |
| Pin 7 | PB6 β Port B, bit 6 (also XTAL1/TOSC1) |
| Pin 8 | PB7 β Port B, bit 7 (also XTAL2/TOSC2) |
| Pin 9 | PD5 β Port D, bit 5 (also T1, OC0B) |
| Pin 10 | PD6 β Port D, bit 6 (also AIN0, OC0A) |
| Pin 11 | PD7 β Port D, bit 7 (also AIN1) |
| Pin 12 | PB0 β Port B, bit 0 (also ICP1, CLKO) |
| Pin 13 | PB1 β Port B, bit 1 (also OC1A) |
| Pin 14 | PB2 β Port B, bit 2 (also OC1B, SS) |
| Pin 15 | PB3 β Port B, bit 3 (also OC2A, MOSI) |
| Pin 16 | PB4 β Port B, bit 4 (also MISO) |
| Pin 17 | PB5 β Port B, bit 5 (also SCK) |
| Pin 18 | AVCC β Analog supply voltage for ADC |
| Pin 19 | ADC6 β Analog input channel 6 |
| Pin 20 | AREF β Analog reference voltage for ADC |
| Pin 21 | GND β Ground |
| Pin 22 | ADC7 β Analog input channel 7 |
| Pin 23 | PC0 β Port C, bit 0 (also ADC0) |
| Pin 24 | PC1 β Port C, bit 1 (also ADC1) |
| Pin 25 | PC2 β Port C, bit 2 (also ADC2) |
| Pin 26 | PC3 β Port C, bit 3 (also ADC3) |
| Pin 27 | PC4 β Port C, bit 4 (also ADC4, SDA) |
| Pin 28 | PC5 β Port C, bit 5 (also ADC5, SCL) |
| Pin 29 | PC6 β Port C, bit 6 (also RESET) |
| Pin 30 | PD0 β Port D, bit 0 (also RXD) |
| Pin 31 | PD1 β Port D, bit 1 (also TXD) |
| Pin 32 | PD2 β Port D, bit 2 (also INT0) |
Typical Applications
ATMEGA168A-AU is suitable for 6 applications: Arduino-Compatible Development Boards, Industrial Sensor Nodes, Battery-Powered IoT Endpoints, Motor Control and Robotics, Home Automation Controllers, Portable Instrumentation.
Arduino-Compatible Development Boards
The ATMEGA168A-AU is the exact MCU used on classic Arduino boards such as the Duemilanove and Diecimila, making it a natural fit for Arduino-compatible designs. Its 16 KB flash accommodates the Arduino bootloader plus a moderate sketch, while the 23 I/O lines map directly to the standard Arduino header layout. The 20 MHz maximum clock and 2.7 V to 5.5 V supply allow operation from either USB 5 V or a 3.3 V regulator. Designers typically pair it with an FT232RL USB-to-serial bridge for programming and a 16 MHz crystal for timing accuracy. The trade-off versus the ATMEGA328P-AU is half the flash and SRAM, so memory-intensive sketches may require the larger device.
Recommended
Industrial Sensor Nodes
The ATMEGA168A-AU suits industrial sensor nodes because its integrated 10-bit ADC, three timer/counters, and USART/SPI/I2C interfaces connect directly to temperature, pressure, and flow sensors without external interface logic. The -40 C to +85 C operating range covers most factory-floor environments, and the 2.7 V to 5.5 V supply tolerates the noisy rails typical of 24 V industrial systems after regulation. A typical node samples an analog sensor through the ADC, processes the reading, and transmits over RS-485 via the USART. The 16 KB flash limits complex protocol stacks, so designs needing TCP/IP or large buffers should migrate to the ATMEGA328P-AU or a 32-bit MCU.
Recommended
Battery-Powered IoT Endpoints
For battery-powered IoT endpoints, the ATMEGA168A-AU offers six sleep modes including Power-down and Power-save, allowing average current in the microamp range between transmissions. The 1 KB SRAM and 512 B EEPROM store sensor calibration data and network credentials without external memory. The integrated watchdog timer with independent oscillator improves reliability in unattended deployments. A typical endpoint wakes on a timer, reads a sensor via I2C, and transmits over a sub-GHz or BLE module through the USART or SPI. The main trade-off is that the A-revision draws more standby current than the picoPower ATMEGA168PA-AU, so power-critical designs should select the PA variant.
Recommended
Motor Control and Robotics
The ATMEGA168A-AU handles motor control and small robotics tasks using its three timer/counters with compare modes to generate PWM for H-bridge drivers. The 16-bit Timer/Counter1 provides precise PWM for motor speed control, while the 10-bit ADC reads potentiometers or current-sense shunts for closed-loop feedback. The 23 I/O lines drive limit switches, encoders, and status LEDs. At 20 MHz the core executes most instructions in one cycle, giving responsive control-loop timing. Designers should note that the 16 KB flash constrains complex motion-planning algorithms, so multi-axis robots typically use the ATMEGA328P-AU or a 32-bit device. Decouple the motor supply from the MCU rail to avoid brown-out resets.
Recommended
Home Automation Controllers
The ATMEGA168A-AU is well suited to home automation controllers that manage relays, dimmers, and sensor inputs. Its 23 I/O lines directly drive relay driver transistors and read wall-switch and PIR inputs, while the Two-Wire serial interface connects to I2C temperature and humidity sensors. The USART can interface with a wireless module for remote control. The 512 B EEPROM stores scene settings and network addresses across power cycles. The 2.7 V to 5.5 V range allows operation from a 5 V USB supply or a 3.3 V regulator. For controllers needing more memory for scheduling logic or display graphics, the ATMEGA328P-AU is a pin-compatible upgrade.
Recommended
Portable Instrumentation
Portable instrumentation benefits from the ATMEGA168A-AU's integrated 10-bit ADC, low sleep-mode current, and compact 32-TQFP package. Handheld multimeters, data loggers, and environmental meters use the ADC to digitize sensor signals and the EEPROM to store calibration constants. The 20 MHz core processes readings and drives a character or segment LCD through the I/O ports. Six sleep modes extend battery life between measurements. The 7x7 mm TQFP footprint keeps the PCB small enough for handheld enclosures. The main limitation is the 16 KB flash, which restricts complex display or logging firmware; designs requiring graphics or large data buffers should use the ATMEGA328P-AU.
Recommended
Recommended Products Summary
Engineering reference data for ATMEGA168A-AU β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ATMEGA168PA-AU | ATMEGA168-20AU | ATMEGA328P-AU | ATMEGA88PA-AU |
|---|---|---|---|---|---|
| Package | 32-TQFP (7x7 mm) | 32-TQFP (7x7 mm) - same | 32-TQFP (7x7 mm) - same | 32-TQFP (7x7 mm) - same | 32-TQFP (7x7 mm) - same |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Flash Memory | 16 KB | 16 KB | 16 KB | 32 KB | 8 KB |
| SRAM | 1 KB | 1 KB | 1 KB | 2 KB | 512 B |
| EEPROM | 512 B | 512 B | 512 B | 1 KB | 512 B |
| Maximum Clock Frequency | 20 MHz | 20 MHz | 20 MHz | 20 MHz | 20 MHz |
| Operating Voltage | 2.7 V to 5.5 V | 1.8 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 |
| I/O Lines | 23 | 23 | 23 | 23 | 23 |
| Low-Power Technology | Standard low-power | picoPower | Standard low-power | picoPower | picoPower |
Key Differentiators
- A-revision brown-out detection and calibrated internal oscillator (vs ATMEGA168-20AU)
- Standard low-power core with full 20 MHz operation at 2.7 V (vs ATMEGA168PA-AU)
- Half the flash and SRAM of the ATMEGA328P-AU at lower cost (vs ATMEGA328P-AU)
- Double the flash and SRAM of the ATMEGA88PA-AU (vs ATMEGA88PA-AU)
Design Notes
Decouple both VCC and AVCC with 100 nF ceramic capacitors placed as close as possible to the respective pins, and add a 10 uF bulk capacitor near the regulator output. AVCC should be connected through a low-pass filter (10 uH inductor or ferrite bead plus 100 nF) when the ADC is used, per the Microchip ATmega168A datasheet recommendation. Keep the analog ground return separate from the digital ground and join them at a single point to minimize ADC noise.
Place the 16 MHz crystal (if used) within 10 mm of the XTAL1/XTAL2 pins and keep the trace lengths short and symmetric. Route the load capacitors (typically 22 pF) directly to the ground plane. Keep high-speed digital traces away from the crystal and AREF pins to avoid coupling. The 32-TQFP 0.8 mm pitch requires a minimum trace width of 0.15 mm and a solder mask dam between pads for reliable assembly.
The RESET pin (PC6) has an internal pull-up but an external 10 kOhm pull-up plus 100 nF capacitor to ground is recommended for noise immunity in industrial environments. Do not leave AREF floating when using the ADC; connect it to AVCC through a 100 nF capacitor or drive it with an external reference. Estimated: at 5 V and 20 MHz the active current is roughly 10-15 mA, so a 100 mA LDO provides adequate margin for the MCU plus peripherals.
When using the USART at high baud rates, keep the TXD/RXD traces short and avoid routing them parallel to switching regulator nodes. For SPI and I2C buses, add 4.7 kOhm pull-ups on SDA/SCL and keep bus capacitance below 400 pF for reliable 400 kHz operation. Series termination resistors (22-33 Ohm) on long SPI clock lines reduce ringing.
Compliance Information
RoHS and REACH compliance per Microchip product page and distributor listings. The ATmega168A is not AEC-Q100 qualified; automotive designs should use the ATmega168PA automotive-grade variants where available.
