JAJSMX5 July   2022 LP5912-EP

PRODUCTION DATA  

  1. 1 特長
  2. 2 アプリケーション
  3. 3 概要
  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
    6. 6.6 Output and Input Capacitors
    7. 6.7 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Enable (EN)
      2. 7.3.2 Output Automatic Discharge (RAD)
      3. 7.3.3 Reverse Current Protection (IRO)
      4. 7.3.4 Internal Current Limit (ISC)
      5. 7.3.5 Thermal Overload Protection (TSD)
      6. 7.3.6 Power-Good Output (PG)
    4. 7.4 Device Functional Modes
      1. 7.4.1 Enable (EN)
      2. 7.4.2 Minimum Operating Input Voltage (VIN)
  8. 8 Applications and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 External Capacitors
        2. 8.2.2.2 Input Capacitor
        3. 8.2.2.3 Output Capacitor
        4. 8.2.2.4 Capacitor Characteristics
        5. 8.2.2.5 Remote Capacitor Operation
        6. 8.2.2.6 Power Dissipation
        7. 8.2.2.7 Estimating Junction Temperature
      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 Example
  9. 9 Device and Documentation Support
    1. 9.1 Documentation Support
      1. 9.1.1 Related Documentation
    2. 9.2 Receiving Notification of Documentation Updates
    3. 9.3 サポート・リソース
    4. 9.4 Trademarks
  10. 10Electrostatic Discharge Caution
  11. 11Glossary
  12. 12Mechanical, Packaging, and Orderable Information

パッケージ・オプション

メカニカル・データ（パッケージ｜ピン）
サーマルパッド・メカニカル・データ
発注情報

8.2.2.6 Power Dissipation

Knowing the device power dissipation and proper sizing of the thermal plane connected to the tab or pad is critical to ensuring reliable operation. Device power dissipation can be calculated with Equation 1, and depends on input voltage, output voltage, and load conditions of the design.

Equation 1. PD(MAX) = (VIN(MAX) – VOUT) × IOUT

Power dissipation can be minimized, and greater efficiency can be achieved, by using the lowest available voltage drop option that is greater than the dropout voltage (VDO). However, keep in mind that higher voltage drops result in better dynamic (that is, PSRR and transient) performance.

On the WSON (DRV) package, the primary conduction path for heat is through the exposed power pad into the PCB. To ensure the device does not overheat, connect the exposed pad (through thermal vias) to an internal ground plane with an appropriate amount of copper PCB area.

According to Equation 2 or Equation 3, 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 2. TJ(MAX) = TA(MAX) + (RθJA × PD(MAX))
Equation 3. PD = (TJ(MAX) – TA(MAX)) / RθJA

Unfortunately, this RθJA is highly dependent on the heat-spreading capability of 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 Section 6.4 table is determined by the specific EIA/JEDEC JESD51-7 standard for PCB and copper-spreading area, and is to be used only as a relative measure of package thermal performance. For a well-designed thermal layout, RθJA is actually the sum of the package junction-to-case (bottom) thermal resistance (RθJCbot) plus the thermal resistance contribution by the PCB copper area acting as a heat sink.