SCHS147J November   1998  – November 2021 CD54HC138 , CD54HC238 , CD54HCT138 , CD54HCT238 , CD74HC138 , CD74HC238 , CD74HCT138 , CD74HCT238

PRODUCTION DATA  

  1. 1 Features
  2. 2 Description
  3. 3 Revision History
  4. 4 Pin Configuration and Functions
    1.     5
  5. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 Recommended Operating Conditions
    3. 5.3 Thermal Information
    4. 5.4 Electrical Characteristics
    5. 5.5 Switching Characteristics (2)
  6. 6 Parameter Measurement Information
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Device Functional Modes
  8. 8 Power Supply Recommendations
  9. 9 Layout
    1. 9.1 Layout Guidelines
  10. 10Device and Documentation Support
    1. 10.1 Documentation Support
      1. 10.1.1 Related Documentation
    2. 10.2 Receiving Notification of Documentation Updates
    3. 10.3 Support Resources
    4. 10.4 Trademarks
    5. 10.5 Electrostatic Discharge Caution
    6. 10.6 Glossary
  11. 11Mechanical, Packaging, and Orderable Information

Package Options

Refer to the PDF data sheet for device specific package drawings

Mechanical Data (Package|Pins)
  • PW|16
  • NS|16
  • N|16
  • D|16
Thermal pad, mechanical data (Package|Pins)
Orderable Information

7.1 Overview

The CDx4HC(T)138 and '238 are high speed silicon gate CMOS decoders well suited to memory address decoding or data routing applications. They contain a single 3:8 decoder.

The CDx4HC(T)138 and '238 have three address select inputs (A2, A1, and A0). The circuit functions as a normal one-of-eight decoder.

Three strobe inputs (G2, G1 and G0) are provided to simplify cascading and to facilitate demultiplexing. When any input strobe is active, all outputs are forced into the high state for the '138 function. When any input strobe is active, all outputs are forced into the low state for the '238 function.

The demultiplexing function is accomplished by first using the select inputs to choose the desired output, and then using one of the strobe inputs as the data input.

The outputs for the CDx4HC(T)138 are normally low when selected. The outputs for the CDxHC(T)238 are normally high when selected.