SLVS647J August   2006  – May 2025 TLE4275-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 Timing Diagrams
    7. 5.7 Typical Characteristics
  7. 6 Parameter Measurement Information
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagrams
    3. 7.3 Feature Description
      1. 7.3.1 Power-Good Reset (RESET)
      2. 7.3.2 Adjustable Power-Good RESET Delay Timer (DELAY)
        1. 7.3.2.1 Setting the Adjustable Power-Good Reset Delay
      3. 7.3.3 Undervoltage Lockout
      4. 7.3.4 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
  9. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Input and Output Capacitor Selection
        1. 8.1.1.1 Legacy Chip Capacitor Selection
        2. 8.1.1.2 New Chip Capacitor Selection
          1. 8.1.1.2.1 Output Capacitor
          2. 8.1.1.2.2 Input Capacitor
      2. 8.1.2 Dropout Voltage
      3. 8.1.3 Reverse Current
      4. 8.1.4 Power Dissipation (PD)
        1. 8.1.4.1 Thermal Performance Versus Copper Area
        2. 8.1.4.2 Power Dissipation Versus Ambient Temperature
      5. 8.1.5 Estimating Junction Temperature
      6. 8.1.6 Setting the Adjustable Power-Good Reset Delay
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Input Capacitor
        2. 8.2.2.2 Output Capacitor
      3. 8.2.3 Application Curves
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
      2. 8.4.2 Layout Examples
  10. 9 Device and Documentation Support
    1. 9.1 Device Support
      1. 9.1.1 Device Nomenclature
      2. 9.1.2 Development Support
    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
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

8.1.4 Power Dissipation (PD)

Circuit reliability requires consideration of the device power dissipation, location of the circuit on the printed circuit board (PCB), and correct thermal plane sizing. Make sure the PCB area around the regulator has few or no other heat-generating devices that cause added thermal stress.

To first-order approximation, power dissipation in the regulator depends on the input-to-output voltage difference and load conditions. The following equation calculates power dissipation (PD).

Equation 3. PD = (VIN – VOUT) × IOUT
Note:

Power dissipation is minimized, and therefore greater efficiency achieved, by correct selection of the system voltage rails. For the lowest power dissipation use the minimum input voltage required for correct output regulation.

For devices with a thermal pad, the primary heat conduction path for the device package is through the thermal pad to the PCB. Solder the thermal pad to a copper pad area under the device. Make sure this pad area contains an array of plated vias that conduct heat to additional copper planes for increased heat dissipation.

The maximum power dissipation determines the maximum allowable ambient temperature (TA) for the device. Power dissipation and junction temperature are most often related by the RθJA of the combined PCB and device package and the TA temperature. RθJA is the junction-to-ambient thermal resistance and TA is the ambient air temperature. The following equations shows this relationship:

Equation 4. TJ = TA + (RθJA × PD)

Thermal resistance (RθJA) is highly dependent on the heat-spreading capability built into the particular PCB design. Therefore, RθJA varies according to the total copper area, copper weight, and location of the planes. The junction-to-ambient thermal resistance listed in the Thermal Information table is determined by the JEDEC standard PCB and copper-spreading area. RθJA is used as a relative measure of package thermal performance.