JAJSF60A April   2018  – December 2018 TPS746

PRODUCTION DATA.  

  1. 1 特長
  2. 2 アプリケーション
  3. 3 概要
    1.     Device Images
      1.      代表的なアプリケーション
  4. 4 改訂履歴
  5. 5 概要（続き）
  6. 6 Pin Configuration and Functions
    1.     Pin Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Timing Requirements
    7. 7.7 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Undervoltage Lockout (UVLO)
      2. 8.3.2 Shutdown
      3. 8.3.3 Foldback Current Limit
      4. 8.3.4 Thermal Shutdown
    4. 8.4 Device Functional Modes
      1. 8.4.1 Device Functional Mode Comparison
      2. 8.4.2 Normal Operation
      3. 8.4.3 Dropout Operation
      4. 8.4.4 Disabled
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Adjustable Device Feedback Resistors
      2. 9.1.2 Input and Output Capacitor Selection
      3. 9.1.3 Dropout Voltage
      4. 9.1.4 Exiting Dropout
      5. 9.1.5 Reverse Current
      6. 9.1.6 Power Dissipation (PD)
      7. 9.1.7 Power-Good Function
    2. 9.2 Feed-Forward Capacitor (CFF)
    3. 9.3 Typical Application
      1. 9.3.1 Design Requirements
      2. 9.3.2 Detailed Design Procedure
        1. 9.3.2.1 Input Current
        2. 9.3.2.2 Thermal Dissipation
      3. 9.3.3 Application Curve
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12デバイスおよびドキュメントのサポート
    1. 12.1 ドキュメントのサポート
      1. 12.1.1 関連資料
    2. 12.2 ドキュメントの更新通知を受け取る方法
    3. 12.3 コミュニティ・リソース
    4. 12.4 商標
    5. 12.5 静電気放電に関する注意事項
    6. 12.6 Glossary
  13. 13メカニカル、パッケージ、および注文情報

9.1.6 Power Dissipation (PD)

Circuit reliability requires consideration of the device power dissipation, location of the circuit on the printed circuit board (PCB), and correct sizing of the thermal plane. The PCB area around the regulator must have 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. Equation 4 calculates power dissipation (PD).

Equation 4. PD = (VIN – VOUT) × IOUT

NOTE

Power dissipation can be minimized, and therefore greater efficiency can be 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. This pad area must contain 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. According to Equation 5, 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 5. TJ = TA + (RθJA × PD)

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 junction-to-ambient thermal resistance listed in the Thermal Information table is determined by the JEDEC standard PCB and copper-spreading area, and is used as a relative measure of package thermal performance.