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556-dual-timer-ic

4 min read

Important Note

This entire repo was AI created - including all of the data within. The intent was to A) help me with my personal electronics inventory; and B) see how I could use AI to make that process a bit easier. DO NOT TRUST!

556 Dual Timer IC - Dual Precision Timing Circuit

Details

  • Location: Cabinet-3, Bin 36, Section B
  • Category: Analog ICs
  • Brand: Various (TI, STMicroelectronics, etc.)
  • Part Number: NE556 / LM556
  • Package: 14-DIP
  • Quantity: 6
  • Status: Available
  • Price Range: $0.50-1.25
  • Datasheet: NE556 Datasheet
  • Product URL: https://www.ti.com/product/NE556

Description

The 556 timer is a dual version of the popular 555 timer IC, containing two independent 555 timer circuits in a single 14-pin package. Each timer section operates identically to a standard 555 timer and can be configured independently as astable multivibrators (oscillators), monostable multivibrators (one-shots), or bistable multivibrators (flip-flops). This IC is ideal for applications requiring two timing functions in a compact package.

Specifications

Electrical Characteristics

  • Operating Voltage: 4.5V ~ 16V
  • Supply Current: 6mA (typical, both timers)
  • Output Current: 200mA per timer (source/sink)
  • Frequency Range: 0.1Hz to 500kHz per timer
  • Temperature Stability: 50ppm/°C
  • Timing Accuracy: ±1% (with proper components)

Physical Characteristics

  • Package: 14-DIP (0.300”, 7.62mm)
  • Dimensions: Standard 14-pin DIP package
  • Operating Temperature: 0°C ~ 70°C (commercial), -55°C ~ 125°C (military)
  • Mounting Type: Through Hole

Key Features

  • Two independent 555 timer circuits in one package
  • Each timer can operate in astable or monostable mode
  • High output current capability (200mA per timer)
  • Wide supply voltage range (4.5V-16V)
  • Temperature stable operation
  • TTL and CMOS compatible outputs
  • Shared power supply pins
  • Independent control for each timer

Image

Image needed - Standard 14-pin DIP package IC with NE556 or LM556 markings on top. Consider taking a photo of actual component for documentation.

Pinout Diagram

Pin Descriptions (14-DIP Package)

PinNameFunction
1GNDGround (shared)
2TRIGGER 1Timer 1 trigger input (active low)
3OUTPUT 1Timer 1 output
4RESET 1Timer 1 reset input (active low)
5CONTROL 1Timer 1 control voltage input
6THRESHOLD 1Timer 1 threshold input
7DISCHARGE 1Timer 1 open collector discharge output
8VCCPositive power supply (shared)
9DISCHARGE 2Timer 2 open collector discharge output
10THRESHOLD 2Timer 2 threshold input
11CONTROL 2Timer 2 control voltage input
12RESET 2Timer 2 reset input (active low)
13OUTPUT 2Timer 2 output
14TRIGGER 2Timer 2 trigger input (active low)

Applications

Common use cases and applications for this component:

  • Dual LED flashers with different rates
  • Sequential timing circuits
  • Dual tone generators
  • PWM circuits with two channels
  • Clock generators for digital systems
  • Dual delay circuits
  • Missing pulse detectors (dual channel)
  • Complementary oscillators

Circuit Examples

Dual Astable Oscillator (Different Frequencies)

VCC (Pin 8) ---- +5V to +15V
GND (Pin 1) ---- Ground

Timer 1:
RESET 1 (Pin 4) -- VCC
CONTROL 1 (Pin 5) - 0.01µF capacitor to ground
TRIGGER 1 (Pin 2) - Connected to THRESHOLD 1 (Pin 6)
THRESHOLD 1 (Pin 6) - R1A+R2A to VCC, C1A to ground
DISCHARGE 1 (Pin 7) - R2A to THRESHOLD 1
OUTPUT 1 (Pin 3) -- Output signal 1

Timer 2:
RESET 2 (Pin 12) -- VCC
CONTROL 2 (Pin 11) - 0.01µF capacitor to ground
TRIGGER 2 (Pin 14) - Connected to THRESHOLD 2 (Pin 10)
THRESHOLD 2 (Pin 10) - R1B+R2B to VCC, C1B to ground
DISCHARGE 2 (Pin 9) - R2B to THRESHOLD 2
OUTPUT 2 (Pin 13) -- Output signal 2

Sequential Timer (One-Shot Chain)

Timer 1 configured as astable (clock generator)
Timer 2 configured as monostable (triggered by Timer 1 output)
OUTPUT 1 (Pin 3) -> TRIGGER 2 (Pin 14) through coupling capacitor
Creates sequential timing pulses

Technical Notes

Important technical considerations and features:

  • Each timer section operates independently with identical characteristics to 555
  • Use 0.01µF bypass capacitors on both CONTROL pins (Pins 5 & 11)
  • RESET pins (Pins 4 & 12) should be tied to VCC if not used for control
  • Each output can source or sink up to 200mA independently
  • Shared power supply pins reduce package size but both timers share supply current
  • Cross-coupling between timers can create complex timing relationships
  • Maximum frequency per timer limited by propagation delays (~500kHz)
  • Both DISCHARGE pins provide paths to discharge respective timing capacitors
  • Can be used to create complementary or sequential timing signals

Tags

timer-ic, analog-ic, dual-timer, precision-timer, astable, monostable, 556 cabinet-3 bin-36 status-available

Notes

The 556 dual timer is essentially two 555 timers in a single package, making it ideal for applications requiring two timing functions. It’s particularly useful for creating sequential timing circuits, dual-rate flashers, or complementary oscillators. The shared power supply pins make it more compact than using two separate 555 ICs, while maintaining full independence of each timer section. Having 6 of these ICs provides good flexibility for complex timing projects that require multiple synchronized or independent timing functions.

Graph View

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