SLVS351Q September   2002  – June 2025 TPS796

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 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 Active Discharge (New Chip)
      2. 6.3.2 Shutdown
      3. 6.3.3 Start-Up
      4. 6.3.4 Undervoltage Lockout (UVLO)
      5. 6.3.5 Regulator Protection
        1. 6.3.5.1 Current Limit
        2. 6.3.5.2 Thermal Shutdown
    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 Recommended Capacitor Types
      2. 7.1.2 Input and Output Capacitor Requirements
      3. 7.1.3 Feed-forward Capacitor (CFF)
      4. 7.1.4 Adjustable Configuration
      5. 7.1.5 Load Transient Response
      6. 7.1.6 Dropout Voltage
        1. 7.1.6.1 Exiting Dropout
      7. 7.1.7 Noise Reduction Pin (legacy chip)
      8. 7.1.8 Power Dissipation (PD)
    2. 7.2 Typical Application
      1. 7.2.1 Design Requirements
      2. 7.2.2 Detailed Design Procedure
      3. 7.2.3 Application Curves
      4. 7.2.4 Best Design Practices
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
        1. 7.4.1.1 Board Layout Recommendation to Improve PSRR and Noise Performance
        2. 7.4.1.2 Regulator Mounting
        3. 7.4.1.3 Estimating Junction Temperature
      2. 7.4.2 Layout Examples
  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. 8.1.2 Device Nomenclature
    2. 8.2 Documentation Support
      1. 8.2.1 Related Documentation
    3. 8.3 Receiving Notification of Documentation Updates
    4. 8.4 Support Resources
    5. 8.5 Trademarks
    6. 8.6 Electrostatic Discharge Caution
    7. 8.7 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

7.1.8 Power Dissipation (PD)

Knowing the device power dissipation and proper sizing of the thermal plane that is connected to the tab or pad is critical to avoiding thermal shutdown and ensuring reliable operation.

As a first-order approximation, power dissipation of the device depends on input voltage and load conditions. Use Equation 5 to approximate PD:

Equation 5. TPS796

Power dissipation can be minimized and greater efficiency can be achieved by using the lowest possible input voltage necessary to achieve the required output voltage regulation.

The main heat conduction path for the device is through the thermal pad on the package or the GND pad for the SOT-223 (DCQ) and TO-263 (KTT) packages. As such, the thermal pad and GND pad must be soldered to a copper pad area under the device. This pad area contains an array of plated vias that conduct heat to any inner plane areas or to a bottom-side copper plane. That tab should be connected to ground.

The maximum power dissipation determines the maximum allowable junction temperature (TJ) for the device. According to Equation 6, power dissipation and junction temperature are most often related by the junction-to-ambient thermal resistance (RθJA) of the combined PCB and device package and the temperature of the ambient air (TA). Equation 7 rearranges Equation 6 for output current.

Equation 6. TJ = TA + (RθJA × PD)
Equation 7. IOUT = (TJ – TA) / [RθJA × (VIN – VOUT)]

Unfortunately, this thermal resistance (RθJA) is highly dependent on the heat-spreading capability built into the particular PCB design, and therefore varies according to the total copper area, copper weight, and location of the planes. The RθJA recorded in the Recommended Operating Conditions table is determined by the JEDEC standard, PCB, and copper-spreading area, and is only used as a relative measure of package thermal performance.