74LS168-Synch Decade Up/Down Counter


The 74LS series of integrated circuits (ICs) was one of the most popular logic families of transistor-transistor logic (TTL) logic chips. 74LS series is a bipolar, low-power Schottky IC. The 74LS168 is a fully synchronous 4-stage up/down counter featuring a preset capability for programmable operation, carry lookahead for easy cascading, and a U/D input to control the direction of counting.

74LS168 Features

  • Low Power Dissipation 100 mW Typical
  • High-Speed Count Frequency 30 MHz Typical
  • Fully Synchronous Operation
  • Full Carry Lookahead for Easy Cascading
  • Single Up/Down Control Input
  • Positive Edge-Trigger Operation

74LS168 Specifications

Supply Voltage4.75 – 5.25Vdc
Maximum Clock Frequency40Mhz
Power Dissipation2mW/gate @100kHz
Minimum Output Current8mA
Propagation Delay10nS
Fan Out (TTL Loads)20

74LS168 Pinout Diagram

74LS168 Pin Description

Pin NoPin NameDescription
1U/DUp-Down Count Control Input
2CPClock Pulse (Active positive-going edge) Input
3P0Parallel Data Input Of Counter 0
4P1Parallel Data Input Of Counter 1
5P2Parallel Data Input Of Counter 2
6P3Parallel Data Input Of Counter 3
7CEPCount Enable Parallel (Active LOW) Input
9PE’Parallel Enable (Active LOW) Input
10CET’Count Enable Trickle (Active LOW) Input
11Q3Counter Output Q3
12Q2Counter Output Q2
13Q1Counter Output Q1
14Q0Counter Output Q0
15TC’Terminal Count (Active LOW) Output
16VCCPositive Supply


  • Clock generation
  • Clock division
  • Integrated oscillator
  • Low power CMOS
  • TTL compatible inputs
  • In frequency counting circuits

74LS168 Alternative Equivalent


Download 74LS168-Synch Decade Up/Down Counter Datasheet from the link given below.