SLLSEY2G March   2017  – August 2021 ISOW7840 , ISOW7841 , ISOW7842 , ISOW7843 , ISOW7844

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Description (continued)
  6. 6 Pin Configuration and Functions
    1.     Pin Functions
  7. 7 Specifications
    1. 7.1  Absolute Maximum Ratings
    2. 7.2  ESD Ratings
    3. 7.3  Recommended Operating Conditions
    4. 7.4  Thermal Information
    5. 7.5  Power Ratings
    6. 7.6  Insulation Specifications
    7. 7.7  Safety-Related Certifications
    8. 7.8  Safety Limiting Values
    9. 7.9  Electrical Characteristics—5-V Input, 5-V Output
    10. 7.10 Supply Current Characteristics—5-V Input, 5-V Output
    11. 7.11 Electrical Characteristics—3.3-V Input, 5-V Output
    12. 7.12 Supply Current Characteristics—3.3-V Input, 5-V Output
    13. 7.13 Electrical Characteristics—5-V Input, 3.3-V Output
    14. 7.14 Supply Current Characteristics—5-V Input, 3.3-V Output
    15. 7.15 Electrical Characteristics—3.3-V Input, 3.3-V Output
    16. 7.16 Supply Current Characteristics—3.3-V Input, 3.3-V Output
    17. 7.17 Switching Characteristics—5-V Input, 5-V Output
    18. 7.18 Switching Characteristics—3.3-V Input, 5-V Output
    19. 7.19 Switching Characteristics—5-V Input, 3.3-V Output
    20. 7.20 Switching Characteristics—3.3-V Input, 3.3-V Output
    21. 7.21 Insulation Characteristics Curves
    22. 7.22 Typical Characteristics
  8. 8 Parameter Measurement Information
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 Electromagnetic Compatibility (EMC) Considerations
      2. 9.3.2 Power-Up and Power-Down Behavior
      3. 9.3.3 Current Limit, Thermal Overload Protection
    4. 9.4 Device Functional Modes
      1. 9.4.1 Device I/O Schematics
  10. 10Application and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
      3. 10.2.3 Application Curve
        1. 10.2.3.1 Insulation Lifetime
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
      1. 12.1.1 PCB Material
    2. 12.2 Layout Example
  13. 13Device and Documentation Support
    1. 13.1 Device Support
      1. 13.1.1 Development Support
    2. 13.2 Documentation Support
      1. 13.2.1 Related Documentation
    3. 13.3 Related Links
    4. 13.4 Receiving Notification of Documentation Updates
    5. 13.5 Support Resources
    6. 13.6 Trademarks
    7. 13.7 Electrostatic Discharge Caution
    8. 13.8 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

12.1 Layout Guidelines

A minimum of four layers is required to accomplish a low-EMI PCB design (see Figure 12-1). Layer stacking should be in the following order (top-to-bottom): high-speed signal layer, ground plane, power plane, and low-frequency signal layer.

  • Routing the high-speed traces on the top layer avoids the use of vias (and the introduction of their inductances) and allows for clean interconnects between the isolator and the transmitter and receiver circuits of the data link.
  • Placing a solid ground plane next to the high-speed signal layer establishes controlled impedance for transmission line interconnects and provides an excellent low-inductance path for the return current flow.
  • Placing the power plane next to the ground plane creates additional high-frequency bypass capacitance of approximately 100 pF/in2.
  • Routing the slower speed control signals on the bottom layer allows for greater flexibility as these signal links usually have margin to tolerate discontinuities such as vias.
  • Keep decoupling capacitors as close as possible to the VCC and VISO pins.

If an additional supply voltage plane or signal layer is needed, add a second power or ground plane system to the stack to keep it symmetrical. This makes the stack mechanically stable and prevents it from warping. Also the power and ground plane of each power system can be placed closer together, thus increasing the high-frequency bypass capacitance significantly.

Because the device has no thermal pad to dissipate heat, the device dissipates heat through the respective GND pins. Ensure that enough copper is present on both GND pins to prevent the internal junction temperature of the device from rising to unacceptable levels.

The integrated signal and power isolation device simplifies system design and reduces board area. The use of low-inductance micro-transformers in the device necessitates the use of high frequency switching, resulting in higher radiated emissions compared to discrete solutions. The device uses on-chip circuit techniques to reduce emissions compared to competing solutions. For further reduction in radiated emissions at system level, refer to the Low-Emission Designs With ISOW7841 Integrated Signal and Power Isolator application report.