SLLSF68 September   2019 THVD1505

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Typical Network Application With Polarity Correction (POLCOR)
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 ESD Ratings [IEC]
    4. 6.4 Recommended Operating Conditions
    5. 6.5 Thermal Information
    6. 6.6 Electrical Characteristics
    7. 6.7 Power Dissipation Characteristics
    8. 6.8 Switching Characteristics
    9. 6.9 Typical Characteristics
  7. 7 Parameter Measurement Information
    1. 7.1 Driver
    2. 7.2 Receiver
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Bus Polarity Correction
        1. 8.3.1.1 Passive Polarity Definition Using Fail-Safe Biasing Network
        2. 8.3.1.2 Active Polarity Definition by the Master Node
    4. 8.4 Device Functional Modes
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Device Configuration
      2. 9.1.2 Bus Design
      3. 9.1.3 Fail-Safe Biasing for Passive Polarity Definition
      4. 9.1.4 Cable Length Versus Data Rate
      5. 9.1.5 Stub Length
      6. 9.1.6 Transient Protection
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
      3. 9.2.3 Application Curve
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
      1. 11.1.1 Design and Layout Considerations For Transient Protection
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Third-Party Products Disclaimer
    2. 12.2 Receiving Notification of Documentation Updates
    3. 12.3 Community Resources
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

11.1.1 Design and Layout Considerations For Transient Protection

Robust and reliable bus node design often requires the use of external transient protection devices in order to protect against surge transients that may occur in industrial environments. Since these transients have a wide frequency bandwidth (from approximately 3 MHz to 300 MHz), high-frequency layout techniques should be applied during PCB design.

  1. Place the protection circuitry close to the bus connector to prevent noise transients from propagating across the board.
  2. Use Vcc and ground planes to provide low inductance. Note that high frequency currents follow the path of least impedance and not the path of least resistance.
  3. Design the protection components into the direction of the signal path. Do not force the transients currents to divert from the signal path to reach the protection device.
  4. Apply 100 to 220-nF decoupling capacitors as close as possible to the VCC pins of transceiver and UART or controller ICs on the board.
  5. Use at least two vias for VCC and ground connections of decoupling capacitors and protection devices to minimize effective via inductance.
  6. Use 1 to 10-k pull-up or pull-down resistors for enable lines to limit noise currents in theses lines during transient events.
  7. Insert pulse-proof resistors into the A and B bus lines if the TVS clamping voltage is higher than the specified maximum voltage of the transceiver bus terminals. These resistors limit the residual clamping current into the transceiver and prevent it from latching up.
    • While pure TVS protection is sufficient for surge transients up to 1 kV, higher transients require metal-oxide varistors (MOVs) which reduce the transients to a few-hundred volts of clamping voltage, and transient blocking units (TBUs) that limit transient current to about 200 mA.