SN74LS138N

Product Overview

• Category: Integrated Circuit (IC)
• Use: Decoder/Demultiplexer
• Characteristics:
  • Low-power Schottky (LS) technology
  • 3-to-8 line decoder/demultiplexer
  • Active low outputs
• Package: DIP (Dual In-line Package)
• Essence: Decodes a three-bit binary input to eight mutually exclusive outputs
• Packaging/Quantity: Available in tubes or reels, quantity varies based on supplier

Specifications

• Supply Voltage: 4.75V to 5.25V
• Input Voltage: 0V to Vcc
• Output Voltage: 0V to Vcc
• Operating Temperature Range: -40°C to +85°C
• Propagation Delay Time: 15ns (max)
• Power Dissipation: 45mW (max)

Detailed Pin Configuration

The SN74LS138N has a total of 16 pins, which are assigned as follows:

1. GND (Ground)
2. A0 (Input A0)
3. A1 (Input A1)
4. A2 (Input A2)
5. E1 (Enable Input 1)
6. E2 (Enable Input 2)
7. E3 (Enable Input 3)
8. Y0 (Output Y0)
9. Y1 (Output Y1)
10. Y2 (Output Y2)
11. Y3 (Output Y3)
12. Y4 (Output Y4)
13. Y5 (Output Y5)
14. Y6 (Output Y6)
15. Y7 (Output Y7)
16. Vcc (Supply Voltage)

Functional Features

• Decodes a three-bit binary input to one of the eight mutually exclusive outputs
• Active low outputs allow easy interfacing with other digital circuits
• Enables individual output selection using the enable inputs (E1, E2, and E3)
• Provides a versatile solution for addressing multiple devices or memory locations

Advantages and Disadvantages

Advantages: - Low-power consumption due to LS technology - Compact DIP package for easy integration into circuit boards - Wide operating temperature range allows usage in various environments

Disadvantages: - Limited to 3-to-8 decoding functionality - Active low outputs may require additional level shifting in certain applications

Working Principles

The SN74LS138N operates based on the principle of binary decoding. It takes a three-bit binary input (A0, A1, and A2) and activates one of the eight outputs (Y0 to Y7) based on the input combination. The enable inputs (E1, E2, and E3) control the output selection. When an enable input is low, the corresponding output is active.

Detailed Application Field Plans

The SN74LS138N finds applications in various fields, including:

1. Address Decoding: Used in microprocessors and memory systems to select specific addresses.
2. Data Multiplexing: Enables data routing in communication systems by selecting different channels.
3. Code Conversion: Converts binary codes to other formats, such as BCD (Binary-Coded Decimal).
4. Control Logic: Implements complex control functions by combining multiple decoders.

Detailed and Complete Alternative Models

1. SN74LS138D: Similar to SN74LS138N but available in SOIC (Small Outline Integrated Circuit) package.
2. CD74HC138E: High-speed CMOS version with similar functionality.
3. 74HC238: Another CMOS decoder/demultiplexer with 3-to-8 functionality.

These alternative models provide similar decoding capabilities and can be used as substitutes for the SN74LS138N in various applications.

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