SLLSFF7B May   2021  – August 2026 ISOW1044

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison Table
  6. 5 Pin Configuration and Functions
  7. 6 Specifications
    1. 6.1  Absolute Maximum Ratings
    2. 6.2  ESD Ratings
    3. 6.3  Recommended Operating Conditions
    4. 6.4  Thermal Information
    5. 6.5  Power Ratings
    6. 6.6  Insulation Specifications
    7. 6.7  Safety-Related Certifications
    8. 6.8  Safety Limiting Values
    9. 6.9  Electrical Characteristics
    10. 6.10 Supply Current Characteristics
    11. 6.11 Switching Characteristics
    12. 6.12 Insulation Characteristics Curves
    13. 6.13 Typical Characteristics
  8. 7 Parameter Measurement Information
  9. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Power Isolation
    3. 8.3 Signal Isolation
    4. 8.4 CAN Transceiver
    5. 8.5 Remote Wake Request Using Wake-Up Pattern (WUP) in Standby Mode
    6. 8.6 Functional Block Diagram
    7. 8.7 Feature Description
      1. 8.7.1 CAN Bus States
      2. 8.7.2 Digital Inputs and Outputs: TXD (Input) and RXD (Output)
      3. 8.7.3 TXD Dominant Timeout (DTO)
      4. 8.7.4 Power-Up and Power-Down Behavior
      5. 8.7.5 Protection Features
      6. 8.7.6 Floating Pins, Unpowered Device
      7. 8.7.7 Glitch-Free Power Up and Power Down
    8. 8.8 Device Functional Modes
    9. 8.9 Device I/O Schematics
  10. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Bus Loading, Length and Number of Nodes
        2. 9.2.2.2 CAN Termination
      3. 9.2.3 Application Curve
        1. 9.2.3.1 Insulation Lifetime
    3. 9.3 Power Supply Recommendations
    4. 9.4 Layout
      1. 9.4.1 Layout Guidelines
      2. 9.4.2 Layout Example
  11. 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
  12. 11Revision History
  13. 12Mechanical, Packaging, and Orderable Information

8.7.6 Floating Pins, Unpowered Device

The ISOW1044 is designed to be best when passive or with no load to the CAN bus if the device is unpowered. The bus pins (CANH, CANL) have extremely low leakage currents when the device is unpowered to avoid loading down the bus which is critical if some nodes of the network are unpowered while the rest of the of network remains in operation.

The device has internal pull-ups on critical pins (TXD and STB) which places the device into known states if the pin floats. This internal bias must not be relied upon by design though, especially in noisy environments, but instead must be considered a failsafe protection feature. When a CAN controller supporting open drain outputs is used, an adequate external pullup resistor must be used to verify that the TXD output of the CAN controller maintains adequate bit timing to the input of the CAN transceiver. See Table 8-3 for more details.