87C751 Microcontroller Technical Summary

Overview

The Philips 87C751 is an enhanced 80C51-based microcontroller that combines the familiar architecture of the 80C51 family with specialized features for efficient system integration. Designed for low-power operation and compact system designs, this microcontroller is particularly suited for applications requiring I2C bus communication and space-constrained implementations. The 87C751 variant provides One-Time Programmable (OTP) EPROM memory, offering flexibility for prototyping and low-to-medium volume production.

Key Features

Core Architecture

• 80C51 based architecture with enhanced features
• Boolean processor for efficient bit manipulation
• CMOS and TTL compatible I/O

Memory Configuration

• 2k × 8 EPROM (87C751 variant)
• 64 × 8 bytes of RAM
• One-Time Programmable plastic package option

Communication Interface

• Integrated Inter-Integrated Circuit (I2C) serial bus interface
• Supports standard I2C communication protocols

Timing and Counters

• 16-bit auto-reloadable counter/timer
• Fixed-rate timer for precise timing operations

Power Management

• Low power consumption design
• Normal operation: <11mA @ 5V, 12MHz
• Idle mode for reduced power consumption
• Power-down mode for minimal power draw

Package Options

• 24-pin DIP (300 mil "skinny DIP")
• 24-pin Shrink Small Outline Package (SSOP)
• 28-pin PLCC (Plastic Leaded Chip Carrier)

Applications

The 87C751 microcontroller is designed for a wide range of applications, particularly where space constraints, power efficiency, and I2C communication are important considerations:

• Consumer Electronics: Remote controls, small appliances, and entertainment systems
• Industrial Control: Sensor interfaces, small control systems, and monitoring devices
• Automotive Systems: Non-critical control functions and sensor interfaces
• Logic Replacement: Where discrete logic would otherwise be used
• Peripheral Control: Keyboard controllers, display interfaces, and small I/O subsystems
• Embedded Systems: Compact designs requiring microcontroller functionality with I2C capability

Electrical Characteristics

Absolute Maximum Ratings

• Supply Voltage (VCC): -0.5V to +7V
• Input Voltage (any pin): -0.5V to VCC+0.5V
• Operating Temperature Range: Commercial (0°C to +70°C) or Industrial (-40°C to +85°C)
• Storage Temperature Range: -65°C to +150°C

DC Characteristics (VCC = 5V ±10%, TA = 0°C to 70°C)

• Power Supply Current (Normal operation @ 12MHz): <11mA
• Power Supply Current (Idle mode @ 12MHz): <3.5mA
• Power Supply Current (Power-down mode): <50μA
• Input Low Voltage (VIL): -0.5V to 0.2VCC
• Input High Voltage (VIH): 0.2VCC to VCC+0.5V
• Output Low Voltage (IOL = 1.6mA): <0.45V
• Output High Voltage (IOH = -60μA): >2.4V

AC Characteristics

• Oscillator Frequency Range: DC to 12MHz
• Machine Cycle: 12 oscillator periods (1μs @ 12MHz)
• I2C Bus Frequency: Up to 100kHz (Standard mode)
• Port Rise/Fall Time: <10ns

Package Information

24-pin DIP (Dual In-line Package)

• Package Type: PDIP (Plastic Dual In-line Package)
• Pitch: 300 mil (7.62mm) - "skinny DIP"
• Dimensions: 32.0mm × 7.62mm × 4.57mm (typical)
• Pin Count: 24
• Operating Temperature: -40°C to +85°C

24-pin SSOP (Shrink Small Outline Package)

• Package Type: SSOP (Shrink Small Outline Package)
• Pitch: 0.65mm
• Dimensions: 8.65mm × 5.6mm × 1.85mm (typical)
• Pin Count: 24
• Operating Temperature: -40°C to +85°C

28-pin PLCC (Plastic Leaded Chip Carrier)

• Package Type: PLCC (Plastic Leaded Chip Carrier)
• Pitch: 1.27mm
• Dimensions: 11.43mm × 11.43mm × 3.05mm (typical)
• Pin Count: 28
• Operating Temperature: -40°C to +85°C

Design Considerations

Oscillator Configuration

The 87C751 can be driven by either a crystal oscillator or external clock source. When using a crystal, typical values range from 1MHz to 12MHz, with appropriate loading capacitors (typically 20-30pF) required for stable operation.

Power Supply Decoupling

Proper decoupling is essential for reliable operation. A 0.1μF ceramic capacitor should be placed as close as possible to the VCC and GND pins, with additional bulk capacitance (10-100μF) recommended for the power supply.

I2C Bus Implementation

The integrated I2C interface requires pull-up resistors on both SDA and SCL lines. Typical values range from 1kΩ to 10kΩ, depending on bus speed and capacitive loading. The bus should be properly terminated to prevent signal reflections in longer implementations.

EPROM Programming

The 87C751 OTP version requires special programming equipment that can provide the necessary programming voltages (typically 12.75V for EPROM programming). Programming should be performed according to the manufacturer's specifications to ensure proper device functionality.

Conclusion

The 87C751 microcontroller provides a cost-effective solution for applications requiring 80C51 compatibility with the added benefit of I2C interface in compact package options. Its low power consumption, flexible memory options, and robust feature set make it suitable for a wide range of embedded control applications. The availability in multiple package types allows designers to select the optimal form factor for their specific application requirements.