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

3 Fix OFF Channel Output Voltage to Ground

As shown in Figure 3-1, the output voltage of OFF channel can be defined by applying any voltage level between VDD and VSS on this (for voltage greater than VDD or less than VSS, the output can be clamped by ESD diodes at VDD or VSS).

Define Output Voltage of OFF Channel Figure 3-1 Define Output Voltage of OFF Channel

The output voltage can be calculated by solving Kirchhoff's Current Law equation:

Equation 3. V D D - V O U T R o f f , u p + V S S - V O U T R o f f , d o w n = V O U T - V X R X

Usually, the recommendation is fix the uncertain OFF-channel voltage to ground so that no unwanted voltage can be read by MCU.

The following three designs are proposed to satisfy this need.