SCAS291W MARCH   1993  – October 2016 SN54LVC138A , SN74LVC138A

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Switching Characteristics—SN54LVC138A
    7. 6.7 Switching Characteristics—SN74LVC138A
    8. 6.8 Operating Characteristics
    9. 6.9 Typical Characteristics
  7. 7 Parameter Measurement Information
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 3-Line to 8-Line Decoder
      2. 8.3.2 1.65-V to 3.6-V Operation With Inputs up to 5.5 V
    4. 8.4 Device Functional Modes
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
      3. 9.2.3 Application Curve
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Related Links
    2. 12.2 Receiving Notification of Documentation Updates
    3. 12.3 Community Resources
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

封装选项

请参考 PDF 数据表获取器件具体的封装图。

机械数据 (封装 | 引脚)
  • W|16
散热焊盘机械数据 (封装 | 引脚)
订购信息

8 Detailed Description

8.1 Overview

The SNx4LVC138A devices are 3-to-8 decoders and demultiplexers. The three input pins, A, B, and C, select which output is active. The selected output is pulled LOW, while the remaining outputs are all HIGH. The conditions at the binary-select inputs at the three enable inputs select one of eight output lines. Two active-low and one active-high enable inputs reduce the requirement for external gates or inverters when expanding. A 24-line decoder can be implemented without external inverters, and a 32-line decoder requires only one inverter. An enable input can be used as a data input for demultiplexing applications.

The conditions at the binary-select inputs and the three enable inputs select one of eight output lines. Two active-low enable inputs and one active-high enable input reduce the need for external gates or inverters when expanding. A 24-line decoder can be implemented without external inverters, and a 32-line decoder requires only one inverter. An enable input can be used as a data input for demultiplexing applications.

8.2 Functional Block Diagram

SN54LVC138A SN74LVC138A ld_cas291.gif

8.3 Feature Description

8.3.1 3-Line to 8-Line Decoder

This device features three binary inputs to select a single active-low output. Three enable pins are also available to enable or disable the outputs. One active high enable and two active low enable pins are available, and any enable pin can be deactivated to force all outputs high. All three enable pins must be active for the output to be enabled.

8.3.2 1.65-V to 3.6-V Operation With Inputs up to 5.5 V

The SN54LVC138A 3-line to 8-line decoder demultiplexer is designed for 2.7-V to 3.6-V VCC operation, and the SN74LVC138A 3-line to 8-line decoder demultiplexer is designed for 1.65-V to 3.6-V VCC operation.

Inputs can be driven from either 3.3-V or 5-V devices. This feature allows the use of these devices as translators in a mixed 3.3-V and 5-V system environment.

8.4 Device Functional Modes

Table 2 lists the outputs of the SNx4LVC138A devices based on the possible input configurations.

Table 2. Function Table

ENABLE INPUTS SELECT INPUTS OUTPUTS
G1 G2A G2B C B A Y0 Y1 Y2 Y3 Y4 Y5 Y6 Y7
X H X X X X H H H H H H H H
X X H X X X H H H H H H H H
L X X X X X H H H H H H H H
H L L L L L L H H H H H H H
H L L L L H H L H H H H H H
H L L L H L H H L H H H H H
H L L L H H H H H L H H H H
H L L H L L H H H H L H H H
H L L H L H H H H H H L H H
H L L H H L H H H H H H L H
H L L H H H H H H H H H H L
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