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90LS8535 - Low-Power CMOS 8-Bit Microcontroller

Overview

The AT90S4434/8535 (including the 90LS8535 variant) is a low-power CMOS 8-bit microcontroller based on the AVR® enhanced RISC architecture. Designed for high performance and efficiency, it executes powerful instructions in a single clock cycle, achieving throughputs approaching 1 MIPS per MHz. This allows system designers to optimize power consumption while maintaining high processing speeds. The microcontroller is ideal for embedded applications requiring a balance of performance, power efficiency, and flexibility.

Key Features

• AVR® Enhanced RISC Architecture – High-performance, low-power RISC design with 118 powerful instructions, most executing in a single clock cycle.
• In-System Programmable Flash Memory –
  • 8K bytes (AT90S/LS8535) or 4K bytes (AT90S/LS4434)
  • SPI serial interface for in-system programming
  • Endurance: 1,000 write/erase cycles
• EEPROM Memory –
  • 512 bytes (AT90S/LS8535) or 256 bytes (AT90S/LS4434)
  • Endurance: 100,000 write/erase cycles
• Internal SRAM –
  • 512 bytes (AT90S/LS8535) or 256 bytes (AT90S/LS4434)
• 8-Channel, 10-Bit ADC – High-resolution analog-to-digital conversion for sensor interfacing.
• 32 x 8 General Purpose Working Registers – Efficient data handling and processing.
• 32 Programmable I/O Lines – Flexible interfacing with external devices.
• Programmable Serial UART – Supports serial communication protocols.
• Wide Operating Voltage Range –
  • 4.0V - 6.0V (AT90S4434/AT90S8535)
  • 2.7V - 6.0V (AT90LS4434/AT90LS8535)
• Speed Grades –
  • 0 - 8 MHz (AT90S4434/AT90S8535)
  • 0 - 4 MHz (AT90LS4434/AT90LS8535)
• Power-On Reset Circuit – Ensures reliable startup.
• Up to 8 MIPS Throughput at 8 MHz – High computational performance.
• Real-Time Counter (RTC) – Separate oscillator and counter mode.
• Multiple Timer/Counters –
  • Two 8-bit timer/counters with prescaler and compare mode
  • One 16-bit timer/counter with prescaler, compare, and capture modes
• 3 PWM Channels – Pulse-width modulation for motor control, LED dimming, etc.
• External and Internal Interrupt Sources – Flexible event handling.
• Programmable Watchdog Timer – On-chip oscillator for system reliability.
• On-Chip Analog Comparator – Simplifies analog signal processing.
• Three Sleep Modes – Idle, Power Save, and Power Down for energy efficiency.
• Programming Lock for Software Security – Protects firmware from unauthorized access.

Applications

The 90LS8535 microcontroller is suitable for a wide range of embedded applications, including but not limited to:

• Industrial Control Systems – Automation, sensor interfacing, and process control.
• Consumer Electronics – Smart home devices, remote controls, and wearable tech.
• Automotive Systems – Dashboard controls, lighting systems, and basic engine management.
• Medical Devices – Portable diagnostic equipment and patient monitoring systems.
• IoT and Wireless Devices – Low-power sensor nodes and communication modules.
• Motor Control – PWM-driven DC and stepper motor applications.
• Power Management – Battery-operated and energy-efficient systems.

Electrical Characteristics

Absolute Maximum Ratings

• Operating Voltage (VCC) – 2.7V to 6.0V (AT90LS variants), 4.0V to 6.0V (AT90S variants)
• Maximum Clock Frequency – 8 MHz (AT90S), 4 MHz (AT90LS)
• Operating Temperature Range – -40°C to +85°C (industrial grade)
• Storage Temperature Range – -65°C to +150°C

Power Consumption

• Active Mode (1 MHz, 3V) – ~0.6 mA (typical)
• Power-Down Mode – ~0.1 µA (typical)

ADC Characteristics

• Resolution – 10-bit
• Sampling Rate – Up to 15 kSPS (depending on clock speed)
• Input Voltage Range – 0V to VCC

Package Information

The 90LS8535 is available in multiple package options, including:

• PDIP (Plastic Dual In-Line Package) – 40 pins, through-hole mounting.
• TQFP (Thin Quad Flat Package) – 44 pins, surface-mount.
• PLCC (Plastic Leaded Chip Carrier) – 44 pins, J-lead design.

Pinout Summary

The microcontroller features 32 programmable I/O pins, organized into four ports (Port A, B, C, D). Key pin functions include:

• VCC / GND – Power supply and ground.
• RESET – Active-low reset input.
• XTAL1 / XTAL2 – Crystal oscillator connections.
• ADC0-ADC7 – Analog input channels.
• PWM Outputs – Three dedicated PWM channels.
• UART (TXD, RXD) – Serial communication pins.
• SPI (MOSI, MISO, SCK, SS) – In-system programming interface.

Conclusion

The 90LS8535 is a versatile, high-performance 8-bit microcontroller that combines the efficiency of the AVR®