Complete Guide to Logic Gates
Decade counter (SN74LS90)
The SN74LS90 is a decade counter (divide by 10). It consists of four master-slave flip-flops and logic for binary/BCD counting. It provides QA...QD outputs; can obtain a square wave of 10 (or cycle of 10) by connecting QD to the clock input. It has synchronous reset and preset. Widely used for BCD digit counters in educational projects.
Datasheet and Pin Diagram
The datasheet provides crucial technical information about this integrated circuit, including pin diagram, electrical characteristics and package information.
The SN74LS90 decade counter is a fundamental component in digital electronics. Its configuration is 4 BCD outputs, 2 clock inputs. Its operation is based on the logic function .
Applications
- BCD digit counters
- Frequency dividers
- Digital clocks
- Event counters
- Sequence generators
This integrated circuit is used in various digital logic applications and embedded systems.
Truth Table
The truth table illustrates the output of the SN74LS90 decade counter for each possible combination of its logic inputs.
| Count | QD | QC | QB | QA |
|---|---|---|---|---|
| 0 | 0 | 0 | 0 | 0 |
| 1 | 0 | 0 | 0 | 1 |
| 2 | 0 | 0 | 1 | 0 |
| 3 | 0 | 0 | 1 | 1 |
| 4 | 0 | 1 | 0 | 0 |
| 5 | 0 | 1 | 0 | 1 |
| 6 | 0 | 1 | 1 | 0 |
| 7 | 0 | 1 | 1 | 1 |
| 8 | 1 | 0 | 0 | 0 |
| 9 | 1 | 0 | 0 | 1 |
Technical Specifications
General Information
BCD Counter (mod-10)
4 BCD outputs, 2 clock inputs
Electrical Characteristics
4.75V - 5.25V
20mA
15ns typ
0掳C to 70掳C
Package Information
DIP-14
0.1" (2.54mm)
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Additional Information
To deepen your understanding of the SN74LS90 decade counter, you can consult additional resources on Boolean algebra and digital circuit design. Experimenting with circuit simulators or building physical circuits will help you consolidate your understanding.