ZHCSTV0K November   2001  – December 2023 LP2992

PRODUCTION DATA  

  1.   1
  2. 1 特性
  3. 2 应用
  4. 3 描述
  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 Electrical Characteristics
    5. 5.5 Thermal Information
    6. 5.6 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 Output Enable
      2. 6.3.2 Dropout Voltage
      3. 6.3.3 Current Limit
      4. 6.3.4 Undervoltage Lockout (UVLO)
      5. 6.3.5 Output Pulldown
      6. 6.3.6 Thermal Shutdown
    4. 6.4 Device Functional Modes
      1. 6.4.1 Device Functional Mode Comparison
      2. 6.4.2 Normal Operation
      3. 6.4.3 Dropout Operation
      4. 6.4.4 Disabled
  8. 7 Application and Implementation
    1. 7.1 Application Information
      1. 7.1.1 Estimating Junction Temperature
      2. 7.1.2 Input and Output Capacitor Requirements
      3. 7.1.3 Noise Bypass Capacitor (CBYPASS)
      4. 7.1.4 Power Dissipation (PD)
      5. 7.1.5 Recommended Capacitor Types
      6. 7.1.6 Reverse Current
    2. 7.2 Typical Application
      1. 7.2.1 Design Requirements
      2. 7.2.2 Detailed Design Procedure
        1. 7.2.2.1 ON/OFF Operation
      3. 7.2.3 Application Curves
  9. 8 Power Supply Recommendations
  10. 9 Layout
    1. 9.1 Layout Guidelines
    2. 9.2 Layout Examples
  11. 10Device and Documentation Support
    1. 10.1 Device Nomenclature
    2. 10.2 Documentation Support
      1. 10.2.1 Related Documentation
    3. 10.3 Receiving Notification of Documentation Updates
    4. 10.4 支持资源
    5. 10.5 Trademarks
    6. 10.6 静电放电警告
    7. 10.7 术语表
  12. 11Revision History
  13. 12Mechanical, Packaging, and Orderable Information

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订购信息

7.1.4 Power Dissipation (PD)

Circuit reliability requires consideration of the device power dissipation, location of the circuit on the printed circuit board (PCB), and correct 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. The following equation 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 the following equation, 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 Section 5.5 table is determined by the JEDEC standard PCB and copper-spreading area, and is used as a relative measure of package thermal performance.