8-bit AVR RISC microcontroller in a SOIC-8 (EIAJ 8S2) package, with 8 KB in-system programmable flash, 512 B EEPROM, and 512 B SRAM. Six I/O lines carry a 4-channel 10-bit ADC, two timer/counters with PWM, a USI for I2C/SPI, an analog comparator, and debugWIRE. It runs 2.7-5.5 V up to 20 MHz (1.8-5.5 V to 10 MHz on the V suffix). The default tiny MCU for small embedded tasks. Every pin is multiplexed; consult the pinout for alternate functions.

Pinout

Pin	Name	Type	Function
1	PB5/PCINT5/RESET/ADC0/dW	bidirectional	Port B bit 5. Multiplexed with active-low external RESET input, PCINT5 pin-change interrupt, ADC channel 0, and debugWIRE (dW) single-wire debug I/O. When the RSTDISBL fuse is programmed, it can serve as a (weak) I/O pin; otherwise it is the reset input.
2	PB3/PCINT3/XTAL1/CLKI/OC1B̄/ADC3	bidirectional	Port B bit 3. Multiplexed with XTAL1 crystal oscillator input, external clock input (CLKI), inverted Timer/Counter1 output-compare B (/OC1B), ADC channel 3, and PCINT3 pin-change interrupt.
3	PB4/PCINT4/XTAL2/CLKO/OC1B/ADC2	bidirectional	Port B bit 4. Multiplexed with XTAL2 crystal oscillator output, system clock output (CLKO), Timer/Counter1 output-compare B (OC1B), ADC channel 2, and PCINT4 pin-change interrupt.
4	GND	power_in	Ground reference (0 V).
5	PB0/MOSI/DI/SDA/AIN0/OC0A/OC1Ā/AREF/PCINT0	bidirectional	Port B bit 0. Heavily multiplexed: SPI MOSI (programming), USI Data-Input (DI, three-wire) / SDA (I2C two-wire), analog comparator positive input (AIN0), Timer/Counter0 output-compare A (OC0A), inverted Timer/Counter1 output-compare A (/OC1A), external ADC voltage reference (AREF), and PCINT0 pin-change interrupt.
6	PB1/MISO/DO/AIN1/OC0B/OC1A/PCINT1	bidirectional	Port B bit 1. Multiplexed with SPI MISO (programming), USI Data-Output (DO, three-wire), analog comparator negative input (AIN1), Timer/Counter0 output-compare B (OC0B), Timer/Counter1 output-compare A (OC1A), and PCINT1 pin-change interrupt.
7	PB2/SCK/USCK/SCL/ADC1/T0/INT0/PCINT2	bidirectional	Port B bit 2. Multiplexed with SPI SCK (programming clock), USI clock (USCK three-wire) / SCL (I2C two-wire clock), ADC channel 1, Timer/Counter0 external clock input (T0), external interrupt 0 (INT0), and PCINT2 pin-change interrupt.
8	VCC	power_in	Supply voltage. 2.7–5.5 V for ATtiny85 (0–20 MHz), 1.8–5.5 V for ATtiny85V (0–10 MHz). Decouple with a 100 nF ceramic close to the pin.

Key specifications

Parameter	Value
Type	8-bit AVR RISC microcontroller
Flash	8 KB (in-system programmable)
EEPROM	512 B
SRAM	512 B
I/O lines	6
ADC	4-channel 10-bit
Timers	Two 8-bit with PWM
Interfaces	USI (I2C / SPI), debugWIRE
Supply / clock	2.7-5.5 V, 0-20 MHz
Package	SOIC-8 (EIAJ 8S2)
Body (L×W×H)	5.3 × 5.3 × 1.75 mm

Ordering variants

ATtiny85-20SU (SOIC-8, 20 MHz)
ATtiny85V-10SU (SOIC-8, 10 MHz, 1.8 V)

CAD (KiCad official)

Symbol: MCU_Microchip_ATtiny:ATtiny85-20S
Footprint: Package_SO:SOIC-8_5.3x5.3mm_P1.27mm
3D model: SOIC-8 wide / EIAJ (KiCad packages3D)

Provenance

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

Datasheet: Microchip Technology datasheet (234 pp, sha256 0e3fa6a7d608de9b, retrieved 2026-08-17, tier: manufacturer)
Extractor: ds2sf (Claude) — every pin and dimension is cited to a datasheet page; refuses to fabricate.
CAD: KiCad official libraries (CC-BY-SA 4.0).

Datasheet PDF