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LM556 Dual Timer IC

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The LM556 IC is the dual LM555 IC, meaning the LM556 has two timers inside it. Similar to the LM555 IC, LM556 can also be used for all those applications additionally, since this works with CMOS technology, we can have two timers inside a single package with improved characteristics.

 

LM556 Pin Configuration

Pin Number

Pin Name

Description

1,13

Discharge

Open collector output which discharges a capacitor between intervals (in phase with output). 7 I toggle the output from high to low when the voltage reaches 2/3 of the supply voltage

2,12

Threshold

Compares the voltage applied to the terminal with a reference voltage of 2/3 Vcc. The 6 I amplitude of the voltage applied to this terminal is responsible for the set state of the flip-flop

3,11

Control Voltage

Controls the threshold and trigger levels. It determines the pulse width of the output 5 Voltage I waveform. An external voltage applied to this pin can also be used to modulate the output waveform

4,10

Reset

A negative pulse applied to this pin to disable or reset the timer. When not used for reset 4 I purposes, it should be connected to VCC to avoid false triggering

5,9

Out

This pin is normally connected to load as it is the only pin with output-driven waveform

6,8 Trigger Responsible for the transition of the flip-flop from set to reset. The output of the timer depends 2 I on the amplitude of the external trigger pulse applied to this pin
7 Ground Ground Reference Voltage 0V
14 Vcc Supply Voltage (Typical = 5V, Maximum = 18V)

 

Features

  • Two precision Timers in one single package
  • Typical operating voltage is +5V, can withstand a maximum of +18V.
  • The source/sink current of the output pin is 200mA
  • Supply Current: 10mA
  • Operating Temperature: 0 to 70°C
  • Available in 14-pin SOIC, and MDIP packages

 

Note: Complete Technical Details can be found in the LM556 datasheet given at the end of this page.

 

Other Dual Timer IC: NE556

 

Where to use the LM556 IC

The LM556 IC is the dual LM555 IC, meaning the LM556 has two timers inside it. Similar to the LM555 IC, LM556 can also be used for all those applications additionally, since this works with CMOS technology, we can have two timers inside a single package with improved characteristics.

So if you are looking for a modern replacement for the 555 Timer IC, then LM556 might be the right choice for you.

 

Difference between NE556 and LM556 IC

There is no difference between LM556 and NE556 except the source/sink current of the output pin. According to the LM556 TI datasheet, it is the direct replacement for NE556. So you can use LM556 in place of NE556 without changing anything.

 

How to use the LM556 IC

Application wise both 555 and 556 are the same. Since the LM556 is a 14-pin dual timer package there are two sets of all the timer pins (Threshold, Out, Trigger, Control Voltage, Discharge), and both the timer share the same Vcc and ground pins.

 

Timer IC’s are the most commonly used ICs for timing and Pulse generation applications. They can adapt themselves to various applications due to its different operating modes. They are very simple to understand and if we take a look at the components present inside as shown below

LM556 Internal Circuit

There are three resistors of value 5K, which gives this IC the iconic name “555 Timer”. It has dual comparators and flip-flop which will make this IC operated in three different modes such as Astable, Monostable, and Bistable(Schmitt) Mode. 

 

Applications

  • Time Delay Generation
  • Pulse Width Modulation
  • Pulse generation
  • Precision Timing
  • Sequential Timing circuits

 

2D model (PDIP)         

LM556 Dimensions

Component Datasheet

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