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

9.1.6 Transient Protection

The bus terminals of the THVD1505 transceiver family possess on-chip ESD protection against ±16 kV HBM, ±8 kV IEC 61000-4-2 contact discharge and ±2 kV IEC 61000-4-4 EFT. The International Electrotechnical Commission (IEC) ESD test is far more severe than the HBM ESD test. The 50% higher charge capacitance, CS, and 78% lower discharge resistance, RD of the IEC model produce significantly higher discharge currents than the HBM model.

THVD1505 HBM_app_llse11.gifFigure 25. HBM and IEC ESD Models and Currents in Comparison (HBM Values in Parenthesis)

The on-chip implementation of IEC ESD and EFT protection significantly increases the robustness of equipment. Common discharge events occur because of human contact with connectors and cables. EFTs are generally caused by relay-contact bounce or the interruption of inductive loads.

Surge transients often result from lightning strikes (direct strike or an indirect strike which induce voltages and currents), or the switching of power systems, including load changes and short circuit switching. These transients are often encountered in industrial environments, such as factory automation and power-grid systems.

Figure 26 compares the pulse-power of the EFT and surge transients with the power caused by an IEC ESD transient. The left hand diagram shows the relative pulse-power for a 0.5-kV surge transient and 4-kV EFT transient, both of which dwarf the 10-kV ESD transient visible in the lower-left corner. 500-V surge transients are representative of events that may occur in factory environments in industrial and process automation. The right hand diagram shows the pulse-power of a 6-kV surge transient, relative to the same 0.5-kV surge transient. 6-kV surge transients are most likely to occur in power generation and power-grid systems.

Designers may choose to implement protection against longer duration surge transients. Figure 28 suggests two circuit designs providing protection against short and long duration surge transients. Table 3 lists the bill of materials for the external protection devices.

NOTE

The unit of the pulse-power changes from kW to MW, thus making the power of the 500-V surge transient almost dropping off the scale.

THVD1505 power_comp_llsed6.gifFigure 26. Power Comparison of ESD, EFT, and Surge Transients

In the case of surge transients, high-energy content is signified by long pulse duration and slow decaying pulse power.

The electrical energy of a transient that is dumped into the internal protection cells of the transceiver is converted into thermal energy. This thermal energy heats the protection cells and literally destroys them, thus destroying the transceiver. Figure 27 shows the large differences in transient energies for single ESD, EFT, and surge transients as well as for an EFT pulse train, commonly applied during compliance testing.

THVD1505 comp_trans_llsed6.gifFigure 27. Comparison of Transient Energies

Table 3. List of Components

DEVICE FUNCTION ORDER NUMBER(1) MANUFACTURER
XCVR 5-V, 1-Mbps RS-485 Transceiver THVD1505DR TI
R1, R2 10-Ω, Pulse-Proof Thick-Film Resistor CRCW0603010RJNEAHP Vishay
TVS Bidirectional 400-W Transient Voltage Suppressor CDSOT23-SM712 Bourns
TBU1, TBU2 Bidirectional 200mA Transient Blocking Unit TBU-CA-065-200-WH Bourns
MOV1, MOV2 200-mA Transient Blocking Unit 200-V, Metal-Oxide Varistor MOV-10D201K Bourns
THVD1505 prot_app_llse11.gifFigure 28. Transient Protections Against Surge Transients

The left circuit shown in Figure 28 provides surge protection of 1-kV transients, while the right protection circuits can withstand surge transients of 5 kV.