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74LS90 BCD Counter IC

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Pin Configuration

Pin No.

Pin Name

Description

1

CLKB

Clock Input 2

2

R1

Reset 1

3

R2

Reset 2

4

NC

Not Connected

5

Vcc

Positive Supply Input

6

R3

Reset 3

7

R4

Reset 4

8

Qc

Output Pin 3

9

Qb

Output Pin 2

10

Gnd

Ground

11

Qd

Output Pin 4

12

Qa

Output Pin 1

13

NC

Not Connected

14

CLKA

Clock Input 1

 

Features and Specifications

  • Typical power dissipation: 45mW
  • High count rates: 42MHz
  • Choice of counting modes
  • Input Clamp Diodes Limit High-Speed Termination Effect
  • Supply voltage: 5V
  • Operating Ambient Temperature Range: –55 to 125°C

 

Equivalents

74LS92, 74LS93

 

Brief About 7490 IC

74LS90 is basically a MOD-10 decade counter that generate a BCD output code. It consists of four master-slave JK flip-flop, which are internally connected to provide MOD-2 (count to 2) counter and MOD-5 counter. 74LS90 also have an independent toggle JK flip-flop by CLKA and other three are driven by the CLKB.

Internal Logic Diagram

 74LS90 IC Internal Block Diagram

 

How to Use Decade Counter IC?

The below circuit diagram is for BCD decade counter, by giving HIGH and LOW logic to the CLKA pin, IC start counts from zero to 8 at every HIGH logic. If you want to display the number on a 7-segment display you need a seven segment display driver IC.

 Circuit using 74LS90 BCD counter IC

 

2D-model

74LS90 2D-model





Download Datasheet PDF:
74LS90 BCD Counter IC Datasheet