ZHCSSO4D September   2010  – December 2023 TPS74801-Q1

PRODUCTION DATA  

  1.   1
  2. 1 特性
  3. 2 应用
  4. 3 说明
  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: IOUT = 50 mA
    7. 5.7 Typical Characteristics: IOUT = 1 A
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 Programmable Soft-Start
      2. 6.3.2 Sequencing Requirements
      3. 6.3.3 Output Noise
      4. 6.3.4 Enable and Shutdown
      5. 6.3.5 Power Good
      6. 6.3.6 Internal Current Limit
      7. 6.3.7 Thermal Protection
    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
    2. 7.2 Typical Application
      1. 7.2.1 Design Requirements
      2. 7.2.2 Detailed Design Procedure
        1. 7.2.2.1 Input, Output, and Bias Capacitor Requirements
        2. 7.2.2.2 Transient Response
      3. 7.2.3 Application Curves
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
        1. 7.4.1.1 Layout Recommendations and Power Dissipation
        2. 7.4.1.2 Estimating Junction Temperature
      2. 7.4.2 Layout Example
  9. 8 Device and Documentation Support
    1. 8.1 Documentation Support
      1. 8.1.1 Related Documentation
      2. 8.1.2 Device Nomenclature
    2. 8.2 接收文档更新通知
    3. 8.3 支持资源
    4. 8.4 Trademarks
    5. 8.5 静电放电警告
    6. 8.6 术语表
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

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7.4.1.2 Estimating Junction Temperature

Using the thermal metrics ΨJT and ΨJB, as shown in the Thermal Information table, the junction temperature can be estimated with corresponding formulas (given in Equation 7). For backwards compatibility, an older RθJC,Top parameter is listed as well.

Equation 7. GUID-DA650505-F492-4806-9E0F-5D59BED771A0-low.gif

Where PD is the power dissipation shown by Equation 7, TT is the temperature at the center-top of the device package, and TB is the PCB temperature measured 1mm away from the device package on the PCB surface (see Figure 7-6).

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.

In reference to Figure 7-5, the new thermal metrics (ΨJT and ΨJB) have very little dependency on board size. That is, using ΨJT or ΨJB with Equation 7 is a good way to estimate TJ by simply measuring TT or TB, regardless of the application board size.

GUID-20230807-SS0I-MBBP-KLGF-0PSVSGTWBLNQ-low.gif Figure 7-5 ΨJT and ΨJB vs Board Size

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

GUID-20230807-SS0I-9NNN-BGWK-M8MQZD4LXH8R-low.jpg
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 7-6 Measuring Points for TT and TB