SBVS099H november   2007  – april 2023 TPS74701

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 6 Specifications
    1. 6.1  Absolute Maximum Ratings
    2. 6.2  ESD Ratings
    3. 6.3  Recommended Operating Conditions
    4. 6.4  Thermal Information
    5. 6.5  Electrical Characteristics: Other Orderable Devices (non-M3 Suffix)
    6. 6.6  Electrical Characteristics: Orderable Device (M3 Suffix)
    7. 6.7  Typical Characteristics: VEN = VIN (All Other Orderable Devices, Non-M3 Suffix)
    8. 6.8  Typical Characteristics: VEN = VIN = 1.8 V, VOUT = 1.5 V (All Other Orderable Devices, Non-M3 Suffix)
    9. 6.9  Typical Characteristics: IOUT = 50 mA (M3 Suffix)
    10. 6.10 Typical Characteristics: VEN = VIN = 1.8 V, VOUT = 1.5 V (M3 Suffix)
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Programmable Soft-Start
      2. 7.3.2 Enable and Shutdown
      3. 7.3.3 Power Good
      4. 7.3.4 Internal Current Limit
      5. 7.3.5 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Normal Operation
      2. 7.4.2 Dropout Operation
      3. 7.4.3 Disabled
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Input, Output, and Bias Capacitor Requirements
      2. 8.1.2 Transient Response
      3. 8.1.3 Dropout Voltage
      4. 8.1.4 Sequencing Requirements
      5. 8.1.5 Output Noise
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
      3. 8.2.3 Application Curves
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
        1. 8.4.1.1 Power Dissipation
        2. 8.4.1.2 Estimating Junction Temperature
      2. 8.4.2 Layout Example
  9. 9 Device and Documentation Support
    1. 9.1 Device Support
      1. 9.1.1 Development Support
        1. 9.1.1.1 Evaluation Module
        2. 9.1.1.2 Spice Models
      2. 9.1.2 Device Nomenclature
    2. 9.2 Documentation Support
      1. 9.2.1 Related Documentation
    3. 9.3 Receiving Notification of Documentation Updates
    4. 9.4 Support Resources
    5. 9.5 Trademarks
    6. 9.6 Electrostatic Discharge Caution
    7. 9.7 Glossary
  10. 10Mechanical, Packaging, and Orderable Information

8.4.1.2 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 6). For backwards compatibility, an older RθJC, Top parameter is listed as well.

Equation 6. GUID-DA650505-F492-4806-9E0F-5D59BED771A0-low.gif

where:

  • PD is the power dissipation shown by Equation 5
  • TT is the temperature at the center-top of the device package
  • TB is the PCB temperature measured 1mm away from the device package on the PCB surface (as Figure 8-9 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.

From Figure 8-8, the new thermal metrics (ΨJT and ΨJB) obviously have very little dependency on board size. That is, using ΨJT or ΨJB with Equation 6 is a good way to estimate TJ by simply measuring TT or TB, regardless of the application board size.

GUID-C72FE35D-07EB-4546-BFAC-C56E3C4BD09B-low.gifFigure 8-8 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-75A11547-BD55-44E2-9FCE-0073B905D367-low.gifFigure 8-9 Measuring Points for TT and TB