SCDA008C June   2021  – November 2021 CD4052B , TS3A225E , TS3A44159

 

  1.   Trademarks
  2. 1Introduction
  3. 2Semiconductor Switches
    1. 2.1 NMOS Switch
    2. 2.2 PMOS Switch
  4. 3Basic Signal-Switch Structures
    1. 3.1 NMOS Series Switch
    2. 3.2 NMOS/PMOS Parallel Switch
    3. 3.3 NMOS Series Switch with the Charge Pump
  5. 4Key Concerns in Digital-Switch Applications
    1. 4.1  Power and Control Voltage Requirements
    2. 4.2  Rail-to-Rail Operation
    3. 4.3  Undershoot
    4. 4.4  ron
    5. 4.5  Cio(off)
    6. 4.6  Cio(on)
    7. 4.7  Ci (Control Input Capacitance)
    8. 4.8  Leakage Current
    9. 4.9  Enable and Disable Delays and Propagation Delay
    10. 4.10 Partial Power Down
    11. 4.11 Voltage Translation
  6. 5Signal Switch Families
    1. 5.1 CBT-C Family
      1. 5.1.1 Characteristics of CBT-C Family
        1. 5.1.1.1 VOvs VI
        2. 5.1.1.2 ron vs VI
        3. 5.1.1.3 Undershoot Protection
      2. 5.1.2 Application of CBT-C Family
        1. 5.1.2.1 Bus Isolation
    2. 5.2 CBTLV Family
      1. 5.2.1 Characteristics of the CBTLV Family
    3. 5.3 CB3Q Family
      1. 5.3.1 Characteristics of the CB3Q Family
        1. 5.3.1.1 VOvs VI
        2. 5.3.1.2 ron vs VI
        3. 5.3.1.3 Operation at High Frequency
        4. 5.3.1.4 Output Skew
        5. 5.3.1.5 Frequency Response
        6. 5.3.1.6 Adjacent Channel Crosstalk
      2. 5.3.2 Application of the CB3Q Family
        1. 5.3.2.1 Multiplexer in USB Applications
    4. 5.4 CB3T Family
      1. 5.4.1 Characteristics of the CB3T Family
        1. 5.4.1.1 VO vs VI
        2. 5.4.1.2 ron vs VI
        3. 5.4.1.3 Operation at High Frequency
      2. 5.4.2 Application of the CB3T Family
        1. 5.4.2.1 Voltage Translation for an External Monitor Terminal in a Notebook PC
  7. 6Applications
    1. 6.1 Multiplexing USB Peripherals
    2. 6.2 Multiplexing Ethernet
    3. 6.3 Notebook Docking Station
  8. 7Conclusion
  9. 8References
  10. 9Revision History
  11.   A Test Measurement Circuits
    1.     A.1 Measurement Setup for ron
    2.     A.2 Measurement Setup for VO vs VI Characteristics
    3.     A.3 Voltage-Time Waveform Measurement (Switch On)
    4.     A.4 Voltage-Time Waveform Measurement (Switch Off)
    5.     A.5 Output-Skew Measurement
    6.     A.6 Simulation Setup for Undershoot Measurement
    7.     A.7 Laboratory Setup for Attenuation Measurement
    8.     A.8 Laboratory Setup for Off Isolation Measurement
    9.     A.9 Laboratory Setup for Crosstalk Measurement

4.1 Power and Control Voltage Requirements

One of the first considerations that must be made when selecting a switch is the supply rail voltage and the allowable input range of the signals passed through the switch. As shown in Figure 4-1, the CBT/CBT-C family of devices supports 5 V supply rails, while the CB3T, CBTLV, and CB3Q families support 2.5 V and 3.3 V rails. The dark blue regions indicate the voltage range of signals that are able to be passed through the switch. In some cases, these ranges match the supply voltage (CBT/CBT-C and CBTLV), while other switch families may pass signals that extend beyond the supply rail (CB3T and CB3Q). System requirements may dictate which devices can be used in a particular application. For example, designs implementing a 5 V supply rail and a 5 V signal are likely best served by a device in the CBT/CBT-C family, while a design using a 3.3 V supply rail and a 4 V signal are best served by a device in the CB3T or CB3Q family.

GUID-20211102-SS0I-Z7GC-BRQX-R9Q8XFXJ7GHR-low.gifFigure 4-1 Control Signal Levels (VIH, VIL) and Supply Voltage

The input thresholds of these devices allow users to implement 3.3 V logic or 5 V logic, regardless of the supply voltage or signal voltage being used in design. The red bars in Figure 4-1 show the logic level voltage thresholds for the different digital switch families.