JAJS410O December   2005  – October 2024 TPS74201

PRODUCTION DATA  

  1.   1
  2. 1 特長
  3. 2 アプリケーション
  4. 3 概要
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
    6. 5.6 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 Enable and Shutdown
      2. 6.3.2 Power-Good (VQFN Packages Only)
      3. 6.3.3 Internal Current Limit
    4. 6.4 Device Functional Modes
      1. 6.4.1 Normal Operation
      2. 6.4.2 Dropout Operation
      3. 6.4.3 Disabled
  8. 7 Application and Implementation
    1. 7.1 Application Information
      1. 7.1.1 Input, Output, and Bias Capacitor Requirements
      2. 7.1.2 Transient Response
      3. 7.1.3 Dropout Voltage
      4. 7.1.4 Output Noise
      5. 7.1.5 Programmable Soft-Start
      6. 7.1.6 Sequencing Requirements
    2. 7.2 Typical Applications
      1. 7.2.1 Design Requirements
      2. 7.2.2 Detailed Design Procedure
      3. 7.2.3 Application Curves
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
      2. 7.4.2 Layout Example
      3. 7.4.3 Thermal Protection
      4. 7.4.4 Thermal Considerations
  9. 8 Device and Documentation Support
    1. 8.1 Device Support
      1. 8.1.1 Development Support
        1. 8.1.1.1 Evaluation Modules
        2. 8.1.1.2 Spice Models
    2. 8.2 Documentation Support
      1. 8.2.1 Related Documentation
      2. 8.2.2 Device Nomenclature
    3. 8.3 ドキュメントの更新通知を受け取る方法
    4. 8.4 サポート・リソース
    5. 8.5 Trademarks
    6. 8.6 静電気放電に関する注意事項
    7. 8.7 用語集
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

パッケージ・オプション

メカニカル・データ（パッケージ｜ピン）
サーマルパッド・メカニカル・データ
発注情報

7.4.4 Thermal Considerations

Using the thermal metrics ΨJT and ΨJB, shown in Section 5.4, the junction temperature can be estimated with corresponding formulas (given in Equation 6). For backwards compatibility, an older θJC,Top parameter is listed as well.

 

Equation 6. TPS74201

where

  • PD is the power dissipation given by PD = (VIN – VOUT) × IOUT
  • TT is the temperature at the center-top of the IC package
  • TB is the PCB temperature measured 1mm away from the IC package on the PCB surface (as Figure 7-10 shows).
Note:

Both TT and TB can be measured on actual application boards using a thermo‐gun (an infrared thermometer).

For more information about measuring TT and TB, see the Using New Thermal Metrics application note, available for download at www.ti.com.

TPS74201 Measuring Points for TT and TB
A. TT is measured at the center of both the X- and Y-dimensional axes.
B. TB is measured below the package lead on the PCB surface.
Figure 7-10 Measuring Points for TT and TB

Compared with θJA, the new thermal metrics ΨJT and ΨJB are less independent of board size, but the metrics do have a small dependency. Figure 7-11 shows characteristic performance of ΨJT and ΨJB versus board size.

Looking at Figure 7-11, the RGW package thermal performance has negligible dependency on board size. The KTW package, however, does have a measurable dependency on board size. This dependency exists because the package shape is not point‐symmetric to an IC center. In the KTW package, for example (see Figure 7-10), silicon is not beneath the measuring point of TT, which is the center of the X and Y dimension, so that ΨJT has a dependency. Also, because of that non-point‐symmetry, device heat distribution on the PCB is not point‐symmetric, either, so that ΨJB has a dependency.

TPS74201 ΨJT and ΨJB vs Board SizeFigure 7-11 ΨJT and ΨJB vs Board Size

For a more detailed discussion of why TI does not recommend using θJC,Top to determine thermal characteristics, refer to the Using New Thermal Metrics application note, available for download at www.ti.com. Also, refer to the IC Package Thermal Metrics application note (also available on the TI website) for further information.