74LS90 Decade 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. 74LS90 monolithic counters contain four master-slave flip-flops and additional gating to provide a divide-by-two counter and a three-stage binary counter.

74LS90 Features

  • Contains a divide-by-two Counter and a Three Stage Binary Counter
  • Count Frequency 42MHz
  • Low Power Dissipation
  • Operating Temperature up to 70°C
  • Standard TTL Switching Voltages

74LS90 Specifications

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

74LS90 Pinout Diagram

74LS90 Pin Description

Pin NoPin NameDescription
1CP1′Invert Clear Pin 1
2MR1Master Reset 1
3MR2Master Reset 2
4NCNot Connected
5VCCPositive Supply
6MS1Master Set 1
7MS2Master Set 2
8Q2Output Q2
9Q1Output Q1
10GNDGround Pin
11Q3Output Q3
12Q0Output Q0
13NCNot Connected
14CP0′Invert Clear Pin 0

74LS90 Circuit

Here is a simple circuit of Mod 10 Counter using 74LS90 IC.


  • Clock generation
  • Clock division
  • Integrated oscillator
  • Low power cmos
  • TTL compatible inputs
  • In frequency counting circuit

74LS90 Alternative Equivalent

74LS162, 74LS190

Download 74LS90 Decade Counter Datasheet from the link given below.