SLLS562M August   2009  – February 2022 SN65HVD3082E , SN65HVD3085E , SN65HVD3088E , SN75HVD3082E


  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Pin Configuration and Functions
  6. Specifications
    1. 6.1  Absolute Maximum Ratings
    2. 6.2  ESD Ratings
    3. 6.3  Recommended Operating Conditions
    4. 6.4  Thermal Information, SN65HVD308xE
    5. 6.5  Thermal Information, SNx5HVD3082E
    6. 6.6  Electrical Characteristics: Driver
    7. 6.7  Electrical Characteristics: Receiver
    8. 6.8  Electrical Characteristics
    9. 6.9  Switching Characteristics: Driver
    10. 6.10 Switching Characteristics
    11. 6.11 Typical Characteristics
  7. Parameter Measurement Information
  8. Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
    4. 8.4 Device Functional Modes
  9. Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
        1. Data Rate and Bus Length
        2. Stub Length
        3. Bus Loading
        4. Receiver Fail-safe
      2. 9.2.2 Detailed Design Procedure
        1. Power Usage in an RS-485 Transceiver
        2. Low-Power Shutdown Mode
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
    3. 11.3 Thermal Considerations for IC Packages
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Third-Party Products Disclaimer
    2. 12.2 Related Links
    3. 12.3 Receiving Notification of Documentation Updates
    4. 12.4 Support Resources
    5. 12.5 Trademarks
    6. 12.6 Electrostatic Discharge Caution
    7. 12.7 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

Thermal Considerations for IC Packages

θJA (Junction-to-Ambient Thermal Resistance) is defined as the difference in junction temperature to ambient temperature divided by the operating power.

θJA is not a constant and is a strong function of:

  • the PCB design (50% variation)
  • altitude (20% variation)
  • device power (5% variation)

θJA can be used to compare the thermal performance of packages when the specific test conditions are defined and used. Standardized testing includes specification of PCB construction, test chamber volume, sensor locations, and the thermal characteristics of holding fixtures. θJA is often misused when it is used to calculate junction temperatures for other installations.

TI uses two test PCBs as defined by JEDEC specifications. The low-k board gives average in-use condition thermal performance and consists of a single trace layer 25-mm long and 2-oz thick copper. The high-k board gives best case in-use condition and consists of two 1-oz buried power planes with a single trace layer 25-mm long with 2-oz thick copper. A 4% to 50% difference in θJA can be measured between these two test cards.

θJC (Junction-to-Case Thermal Resistance) is defined as the difference in junction temperature to case divided by the operating power. It is measured by putting the mounted package up against a copper block cold plate, to force heat to flow from the die through the mold compound and into the copper block.

θJC is a useful thermal characteristic when a heat sink is applied to package. It is NOT a useful characteristic to predict junction temperature, as it provides pessimistic numbers if the case temperature is measured in a non-standard system and junction temperatures are backed out. It can be used with θJB in 1-dimensional thermal simulation of a package system.

θJB (Junction-to-Board Thermal Resistance) is defined to be the difference in the junction temperature and the PCB temperature at the center of the package (closest to the die) when the PCB is clamped in a cold-plate structure. θJB is only defined for the high-k test card.

θJB provides an overall thermal resistance between the die and the PCB. It includes a bit of the PCB thermal resistance (especially for BGAs with thermal balls) and can be used for simple 1-dimensional network analysis of package system (see Figure 11-2).

GUID-16CDFCBE-99B5-45E3-B4AD-2C389490393B-low.gifFigure 11-2 Thermal Resistance