ATMEGA8535-16PI - 8-bit AVR MCU 16MHz 8KB Flash | Microchip
MPN: ATMEGA8535-16PI ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $2.49 | $2.49 |
| 10 | $2.24 | $22.40 |
| 100 | $1.99 | $199.00 |
| 500 | $1.79 | $895.00 |
| 1,000 | $1.65 | $1,650.00 |
ATMEGA8535-16PI Overview
An 8-bit AVR microcontroller is a single-chip processor built on the AVR enhanced RISC architecture, in which most of its instructions execute in a single clock cycle. Within the embedded-systems hierarchy, it belongs to the microcontroller unit (MCU) category: CPU, program memory, data memory, timers, serial interfaces, and analog-to-digital conversion integrated onto one die, replacing multi-chip processor-plus-peripheral designs in cost- and size-sensitive control applications.
Key differentiating specifications include up to 16 MIPS throughput at 16 MHz, 130 powerful instructions with mostly single-cycle execution, and 32 general-purpose working registers directly connected to the ALU. The device integrates three flexible timer/counters with compare modes, a programmable serial USART, a byte-oriented Two-wire Serial Interface (I2C-compatible TWI), and an SPI serial port, plus brown-out detection, power-on reset, PWM capability, and a watchdog timer.
Architecturally, the ATmega8535 uses a Harvard-structure AVR core with single-level pipelined instruction fetch, while the Flash program memory supports Read-While-Write self-programming for field firmware updates. The internal 10-bit successive-approximation ADC with 8 multiplexed channels (PA0-PA7) plus an internal bandgap reference input makes external signal-conditioning ICs unnecessary for many sensor tasks. An AT90S8535 compatibility mode, selected by the S8535C fuse, eases migration from the earlier AVR generation.
Typical applications include industrial control and automation panels, motorized motion platforms, HVAC and appliance controllers, and instrumentation front-ends that exploit the 8-channel 10-bit ADC. The 40-pin PDIP package also suits through-hole prototyping, educational boards, and repair of legacy equipment.
Design consideration: the -16PI speed grade requires a 4.5V to 5.5V supply, so it cannot run at 3.3V; plan level shifting for mixed-voltage systems and decouple AVCC/AGND separately for accurate ADC results.
This page synthesizes distributor pricing, drop-in alternative analysis, pinout data, and practical design notes not found in the manufacturer datasheet, with pricing referenced as of 2026-09-19.
Drop-in alternatives for ATMEGA8535-16PI — 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 ATMEGA8535-16PI (same form factor and footprint) — differing in Instructions, Package, Operating Temperature, Communication Interfaces, SRAM.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
ATMEGA8535-16PU
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$2.05 / Unit
View Datasheet →ATMEGA16-16PI
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$3.72 / Unit
View Datasheet →ATMEGA32A-PI
✅ Drop-In ⚠️ 参数待验证📋 Reference alternative (not in catalog)
ATMEGA8515-16PI
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$4.18 / Unit
View Datasheet →AT90S8535-16PI
✅ Drop-In📋 Reference alternative (not in catalog)
ATMEGA8535-16PI Maximum Ratings & Electrical Characteristics
| Core Processor | AVR |
| Core Size | 8-bit |
| Speed | 16 MHz |
| Program Memory Size | 8 KB (4K x 16) Flash |
| Program Memory Type | FLASH (In-System Programmable) |
| RAM Size | 512 x 8 |
| EEPROM Size | 512 x 8 |
| Number of I/O | 32 |
| ADC Channels | 8-channel 10-bit |
| Connectivity | I2C, SPI, UART/USART |
| Peripherals | Brown-out Detect/Reset, POR, PWM, WDT |
| Supply Voltage | 4.5 V to 5.5 V |
| Package | 40-PDIP (0.600 inch, 15.24 mm) |
| Mounting Type | Through Hole |
| MIPS Throughput | 16 MIPS at 16 MHz |
| Instructions | 130 powerful instructions, most single-cycle |
| General Purpose Registers | 32 x 8-bit |
| Timer/Counters | Three flexible timer/counters with compare modes |
ATMEGA8535-16PI Pin Configuration
| Pin 1 | PB5 (MOSI) — Port B, SPI Master Output Slave Input |
| Pin 2 | PB6 (MISO) — Port B, SPI Master Input Slave Output |
| Pin 3 | PB7 (SCK/UCSK) — Port B, SPI Serial Clock |
| Pin 4 | RESET — Reset input, active low |
| Pin 5 | VCC — Digital supply voltage |
| Pin 6 | GND — Digital ground |
| Pin 7 | XTAL2 — Oscillator amplifier output |
| Pin 8 | XTAL1 — Oscillator amplifier input / external clock |
| Pin 9 | PD0 (RXD) — Port D, USART receive |
| Pin 10 | PD1 (TXD) — Port D, USART transmit |
| Pin 11 | PD2 (INT0) — Port D, external interrupt 0 |
| Pin 12 | PD3 (INT1) — Port D, external interrupt 1 |
| Pin 13 | PD4 (OC1B) — Port D, Timer/Counter1 output compare B / PWM |
| Pin 14 | PD5 (OC1A) — Port D, Timer/Counter1 output compare A / PWM |
| Pin 15 | PD6 (ICP1) — Port D, Timer/Counter1 input capture |
| Pin 16 | PD7 (OC2) — Port D, Timer/Counter2 output compare / PWM |
| Pin 17 | PC0 (SCL) — Port C, TWI serial clock |
| Pin 18 | PC1 (SDA) — Port C, TWI serial data |
| Pin 19 | PC2 (TCK) — Port C, JTAG test clock |
| Pin 20 | PC3 (TMS) — Port C, JTAG test mode select |
| Pin 21 | PC4 (TDO) — Port C, JTAG test data output |
| Pin 22 | PC5 (TDI) — Port C, JTAG test data input |
| Pin 23 | PC6 (TOSC1) — Port C, Timer oscillator input (32.768 kHz) |
| Pin 24 | PC7 (TOSC2) — Port C, Timer oscillator output |
| Pin 25 | AVCC — ADC supply voltage |
| Pin 26 | GND — Ground (ADC) |
| Pin 27 | AREF — ADC analog reference voltage |
| Pin 28 | PA7 (ADC7) — Port A, analog channel 7 / digital I/O |
| Pin 29 | PA6 (ADC6) — Port A, analog channel 6 / digital I/O |
| Pin 30 | PA5 (ADC5) — Port A, analog channel 5 / digital I/O |
| Pin 31 | PA4 (ADC4) — Port A, analog channel 4 / digital I/O |
| Pin 32 | PA3 (ADC3) — Port A, analog channel 3 / digital I/O |
| Pin 33 | PA2 (ADC2) — Port A, analog channel 2 / digital I/O |
| Pin 34 | PA1 (ADC1) — Port A, analog channel 1 / digital I/O |
| Pin 35 | PA0 (ADC0) — Port A, analog channel 0 / digital I/O |
| Pin 36 | PB0 (XCK/T0) — Port B, USART external clock / Timer0 clock |
| Pin 37 | PB1 (T1) — Port B, Timer/Counter1 external clock |
| Pin 38 | PB2 (INT2/AIN0) — Port B, external interrupt 2 / analog comparator positive input |
| Pin 39 | PB3 (OC0/AIN1) — Port B, Timer0 output compare / analog comparator negative input |
| Pin 40 | PB4 (SS) — Port B, SPI slave select |
Typical Applications
ATMEGA8535-16PI is suitable for 6 applications: Industrial Control and Automation, Motion Control Platforms, Sensor Data Acquisition, Appliance and HVAC Controllers, Legacy Equipment Repair and Maintenance, Education and Prototyping.
Industrial Control and Automation
The ATMEGA8535-16PI fits industrial control panels because its 4.5V to 5.5V tolerance suits legacy 5V industrial rails, its 32 I/O lines drive relays, contactors, and status LEDs directly at 20 mA per pin, and brown-out detection plus a watchdog timer provide the reset integrity demanded by unattended equipment. The 16 MIPS AVR core executes PID loops and sequential logic without an RTOS. In a typical panel, Port A reads analog setpoints via the 8-channel 10-bit ADC while Ports B and D handle keypad scanning and actuator control over TWI or SPI to peripheral expanders. The industrial -40C temperature grade ensures reliability in unheated enclosures.
Recommended
Motion Control Platforms
Motorized motion platforms, including the well-known AC motor controller community designs, historically used the ATMEGA8535-16PI because its three flexible timer/counters with compare modes generate three independent PWM channels for multi-axis motor drives, while the 8-channel 10-bit ADC reads potentiometer joysticks and current-sense shunts for closed-loop feedback. At 16 MIPS, the AVR core executes the position-estimation math for gyro/accelerometer stabilization in real time. The through-hole 40-pin PDIP package simplifies repair and prototyping on hand-soldered control boards, a decisive factor for hobbyist and service-friendly motion systems that must remain maintainable in the field.
Recommended
Sensor Data Acquisition
The on-chip 8-channel 10-bit successive-approximation ADC with an internal bandgap reference makes the ATMEGA8535-16PI a compact acquisition front-end for temperature, pressure, and potentiometer arrays: up to eight single-ended analog inputs are multiplexed to Port A (PA0-PA7) without external converter ICs. For accuracy, AVCC should be decoupled and AREF stabilized, and the ADC prescaler set so the ADC clock stays within the datasheet limit for 10-bit resolution. Sampled data is buffered in the 512-byte SRAM and logged to the 512-byte EEPROM or streamed over USART at 16 MHz-clocked baud rates, giving a single-chip data logger for slowly varying industrial signals.
Recommended
Appliance and HVAC Controllers
White-goods and HVAC control boards benefit from the ATMEGA8535-16PI combination of power-on reset, brown-out detection, watchdog timer, and EEPROM parameter storage, which together deliver the fault recovery and configuration retention these products require. The three timers generate phase-correct PWM for fan and blower control while the ADC reads NTC thermistors on multiple channels for multi-zone temperature monitoring. The 5V-only supply matches the transformer-derived rails common in appliance power supplies, and the industrial temperature grade covers attic, basement, and outdoor unit environments. The 512-byte EEPROM holds calibration and user settings through power cycles without external memory.
Recommended
Legacy Equipment Repair and Maintenance
Because the ATMEGA8535-16PI populated countless 1990s-2000s industrial and medical boards, it remains a staple for repair services. Rochester Electronics' authorized continuation means new-original units are still purchasable, avoiding risky remarked parts. The device's pin compatibility with AT90S8535, ATmega16, ATmega32, and ATmega8515 lets a repair shop substitute whichever same-footprint part is available, reprogramming the S8535C fuse when replacing the older AT90S8535. The through-hole PDIP package permits desolder-and-replace repair with basic tools, and identical ISP programming restores firmware extracted from a donor unit or held in service archives.
Recommended
Education and Prototyping
The ATMEGA8535-16PI is well suited to embedded-systems teaching labs and breadboard prototyping: the 0.6-inch 40-pin PDIP inserts directly into sockets and breadboards without adapters, the 5V supply tolerates student wiring errors better than 3.3V parts, and the full peripheral set - USART, TWI, SPI, three timers, PWM, and an 8-channel 10-bit ADC - supports an entire semester of progressively complex laboratories from blink to data acquisition. Programs load via a simple ISP programmer costing a few dollars, and free AVR-GCC toolchains run on any platform, keeping the complete learning setup within a typical education budget.
Recommended
Recommended Products Summary
Engineering reference data for ATMEGA8535-16PI — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ATMEGA8535-16PU | ATMEGA16-16PI | ATMEGA32A-PI | ATMEGA8515-16PI | AT90S8535-16PI |
|---|---|---|---|---|---|---|
| Package | 40-PDIP (0.600 inch) | 40-PDIP - same | 40-PDIP - same | 40-PDIP - same | 40-PDIP - same | 40-PDIP - same |
| Brand | Microchip Technology (Atmel) | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Atmel (now Microchip) |
| Flash Memory | 8 KB | 8 KB | 16 KB | 32 KB | 8 KB | 8 KB |
| SRAM | 512 B | 512 B | 1 KB | 2 KB | 512 B | 512 B |
| Max Speed | 16 MHz | 16 MHz | 16 MHz | 16 MHz | 16 MHz | 16 MHz |
| Supply Voltage | 4.5 V to 5.5 V | 4.5 V to 5.5 V | 4.5 V to 5.5 V | 4.5 V to 5.5 V | 4.5 V to 5.5 V | 4.0 V to 6.0 V |
| ADC | 8-ch 10-bit | 8-ch 10-bit | 8-ch 10-bit | 8-ch 10-bit | None | 8-ch 10-bit |
Key Differentiators
- Industrial temperature grade in through-hole package (vs ATMEGA8535-16PU)
- Integrated 8-channel 10-bit ADC (vs ATMEGA8515-16PI)
- AT90S8535 migration path with compatibility fuse (vs AT90S8535-16PI)
Design Notes
Estimated: when powering from a 7805-type regulator, budget VCC (up to 20 mA core at 16 MHz) plus per-pin I/O loads (20 mA each) against the regulator rating; keep VCC within 4.5V to 5.5V or the 16 MHz clocking guarantee is void. Decouple each VCC/AVCC pin with 100 nF ceramic caps placed within a few millimeters, plus one bulk 10 uF per board. Ensure RESET (pin 4) has a 10k pull-up; an uncontrolled reset line is the most common field-failure cause on AVR boards.
Separate analog and digital grounds: AGND (pin 26 area) should connect to digital GND at a single star point, and AVCC must be filtered (ferrite bead plus 100 nF) from VCC for the ADC to reach full 10-bit accuracy. Route ADC traces on Port A away from PWM and crystal lines. For the XTAL pair (pins 7-8), keep the crystal and its load capacitors within 10 mm of the pins with guard ground around them to prevent spurious clocking at 16 MHz.
When substituting an ATmega16/ATmega32 on an ATmega8535 board, remember the ATmega16/32 fuse map and register addresses differ from the ATmega8535 - a firmware rebuild, not just reflash, is required, and JTAG enable on PC2-PC5 (fused on by default on ATmega16/32) will steal TWI pins unless disabled. When replacing AT90S8535, set the S8535C compatibility fuse per datasheet 2502S. Also verify EEPROM wear: 100k erase/write endurance is per cell; do not log data every loop iteration.
All 32 I/O lines on the ATmega8535-16PI can source or sink substantial current, but switching many pins simultaneously at 5V causes ground bounce visible on the ADC. Limit simultaneous port-wide switching, or use series resistors (47-100 ohm) on long unshielded outputs driving cables. For USART lines exceeding roughly 30 cm at 115200 baud, add a series resistor and consider an RS-485 transceiver; the internal AVR protection diodes tolerate only small negative ringing on inputs.
Compliance Information
Compliance status not stated in the provided verified web data; the PI suffix denotes industrial temperature grade, not RoHS status. Consult Microchip product page or certificate of conformance for RoHS/REACH declarations.
