SLVS822F March   2009  – April 2024 TPS798-Q1

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  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 Dissipation Ratings
    7. 5.7 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagrams
    3. 6.3 Feature Description
      1. 6.3.1 Adjustable Operation
      2. 6.3.2 Output Capacitance and Transient Response
      3. 6.3.3 Calculating Junction Temperature
      4. 6.3.4 Protection Features
    4. 6.4 Device Functional Modes
      1. 6.4.1 Low-Voltage Tracking
  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
      3. 7.2.3 Application Curves
    3. 7.3 Power Supply Recommendations
      1. 7.3.1 Thermal Considerations
      2. 7.3.2 Thermal Layout Considerations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
      2. 7.4.2 Layout Example
  9. 8 Device and Documentation Support
    1. 8.1 Receiving Notification of Documentation Updates
    2. 8.2 Support Resources
    3. 8.3 Trademarks
    4. 8.4 Electrostatic Discharge Caution
    5. 8.5 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

Package Options

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

6.3.3 Calculating Junction Temperature

Given an output voltage of 5V, an input voltage range of 15V to 24V, an output current range of 0mA to 50mA, and a maximum ambient temperature of 50°C, the maximum junction temperature is calculated as follows.

The power dissipated (PDISS) by the DGN package is equal to:

Equation 2. IOUT(MAX)(VIN(MAX) – VOUT) + IGND(VIN(MAX))

where:

  • IOUT(MAX) = 50mA
  • VIN(MAX) = 24V
  • VOUT = 5V
  • IGND at (IOUT = 50mA, VIN = 24V) = 1mA

Therefore,

Equation 3. PDISS = 50mA (24V – 5V) + 1mA (24V) = 0.974W

The thermal resistance is approximately 60°C/W, based on JEDEC 51-5 profile. Therefore, the junction temperature rise above ambient is approximately equal to:

Equation 4. 0.974W × 60°C/W = 58.44°C

The maximum junction temperature is then equal to the maximum junction temperature rise above ambient plus the maximum ambient temperature or:

Equation 5. TJ max = 50°C + 58.44°C = 108.44°C