LM556N

LM556N Dual Timing Circuit Technical Summary

Overview

The LM556N is a highly stable dual timing circuit capable of generating precise time delays or oscillations. It consists of two independent 555 timer circuits integrated into a single package, sharing only the V_CC and ground connections. Each timer operates independently, allowing for flexible configuration in various timing applications. The device is designed for direct replacement of SE556/NE556 timers, ensuring compatibility with existing designs.

The LM556N is widely used in applications requiring accurate timing control, such as pulse generation, frequency division, and sequential timing. Its robust design and stable performance make it suitable for industrial, automotive, and consumer electronics applications.

Features

• Dual 555 Timers: Two independent 555 timer circuits in a single package.
• Wide Operating Voltage Range: Operates from 4.5V to 16V, making it versatile for various power supply configurations.
• High Output Current: Sink or source up to 200mA per timer, enabling direct drive of relays, LEDs, and other loads.
• Adjustable Duty Cycle: Allows precise control over the output pulse width and frequency.
• Temperature Stability: Performance remains stable over a wide temperature range (-55°C to 125°C).
• Trigger and Reset Capability: Each timer can be independently triggered or reset for flexible operation.
• Direct Replacement: Compatible with SE556/NE556 timers, ensuring easy upgrades or replacements in existing designs.

Applications

The LM556N is suitable for a broad range of timing and pulse generation applications, including:

• Pulse Generation: Produces accurate pulses for digital systems and communication devices.
• Time Delay Circuits: Used in applications requiring precise delays, such as power sequencing and automation.
• Frequency Division: Divides input frequencies for clock generation and signal processing.
• Oscillators: Functions as a square wave oscillator for tone generation and timing references.
• Industrial Control Systems: Provides timing control for relays, motors, and sensors.
• Automotive Electronics: Used in lighting control, wiper timing, and other automotive systems.
• Consumer Electronics: Integrated into toys, timers, and household appliances.

Electrical Characteristics

The following table summarizes the key electrical specifications of the LM556N under typical operating conditions (V_CC = 5V to 15V, T_A = 25°C unless otherwise noted):

• Supply Voltage Range: 4.5V to 16V
• Supply Current (Idle): 10mA (typical) at V_CC = 15V
• Output Current (Sink/Source): 200mA per timer
• Trigger Voltage: 1.67V (typical) at V_CC = 5V
• Threshold Voltage: 3.33V (typical) at V_CC = 5V
• Reset Voltage: 0.4V (max) to ensure proper reset functionality
• Operating Temperature Range: -55°C to 125°C
• Timing Error: ±2% (typical) over full temperature range

Package Information

The LM556N is available in a standard 14-pin DIP (Dual In-line Package) and SOIC (Small Outline Integrated Circuit) package, providing flexibility for through-hole and surface-mount applications. Key package details include:

• Package Type: 14-Pin PDIP (Plastic Dual In-line Package) and 14-Pin SOIC
• Pin Pitch: 2.54mm (PDIP), 1.27mm (SOIC)
• Dimensions:
  • PDIP: 19.3mm x 6.35mm x 4.57mm (L x W x H)
  • SOIC: 8.65mm x 3.91mm x 1.58mm (L x W x H)
• Lead Material: Tin-plated copper for reliable solderability
• Moisture Sensitivity Level (MSL): MSL 1 (Unlimited floor life at ≤30°C/85% RH)

Functional Description

The LM556N integrates two independent 555 timer circuits, each capable of operating in monostable (one-shot) or astable (oscillator) modes. In monostable mode, the timer generates a single pulse of a defined duration when triggered. In astable mode, it produces a continuous square wave with adjustable frequency and duty cycle.

Each timer's operation is determined by external resistors and capacitors connected to the timing pins (R_A, R_B, and C). The trigger and reset inputs provide additional control, allowing for precise timing adjustments and synchronization with other circuits.

Conclusion

The LM556N is a versatile and reliable dual timing circuit, offering two independent 555 timers in a single package. Its wide operating voltage range, high output current, and temperature stability make it suitable for a variety of industrial, automotive, and consumer applications. With its direct replacement compatibility for SE556/NE556 timers, the LM556N simplifies design upgrades and maintenance.