SCDA060 May   2025 CD4053B

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
    1. 1.1 Demultiplexing Application Example in Solar System
    2. 1.2 Application Issue of Unwanted Voltage at OFF Channels
  5. 2OFF Channel Model Analysis
    1. 2.1 Channel Structure
    2. 2.2 Equivalent Resistor Model
  6. 3Fix OFF Channel Output Voltage to Ground
    1. 3.1 Pull-down Resistor
    2. 3.2 Pull-down Capacitor
    3. 3.3 Bleeder Resistor With a Switch
  7. 4Test and Measurement
    1. 4.1 Measurement Considerations
    2. 4.2 Test Result
  8. 5Summary
  9. 6References

1 Introduction

Texas Instruments offers a wide portfolio of analog switches and multiplexers. The general-purpose analog multiplexers CD405xB are digitally-controlled analog switches. Since this is bidirectional and each channel has very similar characteristics in both directions, this can also be used as a demultiplexer.

When these devices are used as multiplexers, the CHANNEL IN/OUT terminals are the inputs and the COMMON OUT/IN terminals are the outputs, and vice versa when used as demultiplexers. As shown in Figure 1-1, for multiplexing application, the unselected (OFF) channels are not connected to the common terminal, which is naturally isolated from the signal conditioning circuits after the multiplexer. However, for demultiplexing application, output channels are always connected to the signal conditioning circuit after the mux. For the OFF channels, this can get unwanted voltage if the output channels are not properly handled.

Typical Multiplexer and Demultiplexer ApplicationFigure 1-1 Typical Multiplexer and Demultiplexer Application