ATMEGA16A-AU from Microchip, in a TQFP-44(10x10). Pinout and pin descriptions extracted from the manufacturer datasheet by ds2sf; symbol, footprint, and 3D from KiCad-official CAD.

Pinout

Pin	Name	Type	Function
1	PB5/MOSI	bidirectional	Port B bit 5. Alternate function: SPI bus Master-Out-Slave-In. Also serves as slave data input during serial programming.
2	PB6/MISO	bidirectional	Port B bit 6. Alternate function: SPI bus Master-In-Slave-Out. Also serves as slave data output during serial programming.
3	PB7/SCK	bidirectional	Port B bit 7. Alternate function: SPI bus serial clock. Also serves as clock during serial programming.
4	RESET	input	Active-low external reset input. A low level longer than the minimum pulse (see datasheet spec) generates a reset even if the clock is not running.
5	VCC	power_in	Digital supply voltage, 2.7-5.5 V.
6	GND	power_in	Ground reference (0 V).
7	XTAL2	output	Output from the inverting oscillator amplifier. Connect to the far side of an external crystal/resonator across XTAL1-XTAL2.
8	XTAL1	input	Input to the inverting oscillator amplifier and internal clock operating circuit. Also the external clock input when using an external clock source.
9	PD0/RXD	bidirectional	Port D bit 0. Alternate function: USART receive data input.
10	PD1/TXD	bidirectional	Port D bit 1. Alternate function: USART transmit data output.
11	PD2/INT0	bidirectional	Port D bit 2. Alternate function: External interrupt source 0 (INT0).
12	PD3/INT1	bidirectional	Port D bit 3. Alternate function: External interrupt source 1 (INT1).
13	PD4/OC1B	bidirectional	Port D bit 4. Alternate function: Timer/Counter1 Output Compare B match output (OC1B), typically used for PWM.
14	PD5/OC1A	bidirectional	Port D bit 5. Alternate function: Timer/Counter1 Output Compare A match output (OC1A), typically used for PWM.
15	PD6/ICP1	bidirectional	Port D bit 6. Alternate function: Timer/Counter1 Input Capture pin (ICP1).
16	PD7/OC2	bidirectional	Port D bit 7. Alternate function: Timer/Counter2 Output Compare match output (OC2), typically used for PWM.
17	VCC	power_in	Digital supply voltage (second VCC pin on TQFP package). Bypass locally with 100 nF.
18	GND	power_in	Ground reference (second GND pin on TQFP package).
19	PC0/SCL	bidirectional	Port C bit 0. Alternate function: Two-wire Serial Interface clock line (SCL). Requires an external pull-up resistor when used as TWI.
20	PC1/SDA	bidirectional	Port C bit 1. Alternate function: Two-wire Serial Interface data line (SDA). Requires an external pull-up resistor when used as TWI.
21	PC2/TCK	bidirectional	Port C bit 2. Alternate function: JTAG Test Clock (TCK). Held by JTAG when the JTAGEN fuse is programmed.
22	PC3/TMS	bidirectional	Port C bit 3. Alternate function: JTAG Test Mode Select (TMS).
23	PC4/TDO	bidirectional	Port C bit 4. Alternate function: JTAG Test Data Out (TDO).
24	PC5/TDI	bidirectional	Port C bit 5. Alternate function: JTAG Test Data In (TDI).
25	PC6/TOSC1	bidirectional	Port C bit 6. Alternate function: Timer Oscillator pin 1 (TOSC1) for the asynchronous Timer/Counter2 when driven by an external 32.768 kHz watch crystal.
26	PC7/TOSC2	bidirectional	Port C bit 7. Alternate function: Timer Oscillator pin 2 (TOSC2) for the asynchronous Timer/Counter2.
27	AVCC	power_in	Analog supply pin for Port A and the ADC. Should be connected to VCC through a filter (typically an LC network) even when the ADC is not used; must not differ from VCC by more than ±0.3 V.
28	GND	power_in	Ground reference (analog GND on TQFP package).
29	AREF	passive	Analog reference input pin for the A/D converter. Decouple with a capacitor to GND (typically 100 nF); may be driven externally or configured internally.
30	PA7/ADC7	bidirectional	Port A bit 7 / ADC channel 7 input. When the ADC is enabled the pin operates as an analog input; otherwise it is a general-purpose digital I/O.
31	PA6/ADC6	bidirectional	Port A bit 6 / ADC channel 6 input.
32	PA5/ADC5	bidirectional	Port A bit 5 / ADC channel 5 input.
33	PA4/ADC4	bidirectional	Port A bit 4 / ADC channel 4 input.
34	PA3/ADC3	bidirectional	Port A bit 3 / ADC channel 3 input.
35	PA2/ADC2	bidirectional	Port A bit 2 / ADC channel 2 input.
36	PA1/ADC1	bidirectional	Port A bit 1 / ADC channel 1 input.
37	PA0/ADC0	bidirectional	Port A bit 0 / ADC channel 0 input.
38	VCC	power_in	Digital supply voltage (third VCC pin on TQFP package).
39	GND	power_in	Ground reference (third GND pin on TQFP package).
40	PB0/XCK/T0	bidirectional	Port B bit 0. Alternate functions: USART external clock (XCK) and Timer/Counter0 external clock input (T0).
41	PB1/T1	bidirectional	Port B bit 1. Alternate function: Timer/Counter1 external clock input (T1).
42	PB2/AIN0/INT2	bidirectional	Port B bit 2. Alternate functions: Analog comparator positive input (AIN0) and external interrupt source 2 (INT2).
43	PB3/AIN1/OC0	bidirectional	Port B bit 3. Alternate functions: Analog comparator negative input (AIN1) and Timer/Counter0 Output Compare match output (OC0), typically used for PWM.
44	PB4/SS	bidirectional	Port B bit 4. Alternate function: SPI slave select input (SS, active low). Must be held high when the SPI is configured as master unless driven as an output.

Key specifications

Parameter	Value
Manufacturer	Microchip
Package	TQFP-44(10x10)
Category	MCU
Pins	44

Ordering variants

ATMEGA16A-AUAU
ATMEGA16A-AUAUR
ATMEGA16A-AUPU
ATMEGA16A-AUMU
ATMEGA16A-AUMUR

CAD (KiCad official)

Symbol: ATMEGA16A-AU
Footprint: Package_QFP:LQFP-44_10x10mm_P0.8mm
3D model: TQFP-44(10x10) (KiCad packages3D, STEP)

Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

Datasheet: Microchip datasheet (19 pp, sha256 191fad2628376ab8, retrieved 2026-08-17, tier: lcsc)
Extractor: ds2sf (Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate.
CAD: KiCad official libraries (CC-BY-SA 4.0).

Datasheet PDF