JAJSO81 October   2022 LM5013

PRODUCTION DATA  

  1. 特長
  2. アプリケーション
  3. 概要
  4. Revision History
  5. Device Comparison Table
  6. Pin Configuration and Functions
  7. Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings_Catalog
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Typical Characteristivcs
  8. Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1  Control Architecture
      2. 8.3.2  Internal VCC Regulator and Bootstrap Capacitor
      3. 8.3.3  Regulation Comparator
      4. 8.3.4  Internal Soft Start
      5. 8.3.5  On-Time Generator
      6. 8.3.6  Current Limit
      7. 8.3.7  N-Channel Buck Switch and Driver
      8. 8.3.8  Schottky Diode Selection
      9. 8.3.9  Enable and Undervoltage Lockout (EN/UVLO)
      10. 8.3.10 Power Good (PGOOD)
      11. 8.3.11 Thermal Protection
    4. 8.4 Device Functional Modes
      1. 8.4.1 Shutdown Mode
      2. 8.4.2 Standby Mode
      3. 8.4.3 Active Mode
      4. 8.4.4 Sleep Mode
  9. Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Custom Design With WEBENCH® Tools
        2. 9.2.2.2 Switching Frequency (RRON)
        3. 9.2.2.3 Buck Inductor (LO)
        4. 9.2.2.4 Schottky Diode (DSW)
        5. 9.2.2.5 Output Capacitor (COUT)
        6. 9.2.2.6 Input Capacitor (CIN)
        7. 9.2.2.7 Type 3 Ripple Network
      3. 9.2.3 Application Curves
    3. 9.3 Power Supply Recommendations
    4. 9.4 Layout
      1. 9.4.1 Layout Guidelines
        1. 9.4.1.1 Compact PCB Layout for EMI Reduction
        2. 9.4.1.2 Feedback Resistors
      2. 9.4.2 Layout Example
        1. 9.4.2.1 Thermal Considerations
  10. 10Device and Documentation Support
    1. 10.1 Device Support
      1. 10.1.1 Third-Party Products Disclaimer
      2. 10.1.2 Development Support
        1. 10.1.2.1 Custom Design With WEBENCH® Tools
    2. 10.2 Documentation Support
      1. 10.2.1 Related Documentation
    3. 10.3 Receiving Notification of Documentation Updates
    4. 10.4 サポート・リソース
    5. 10.5 Trademarks
    6. 10.6 Electrostatic Discharge Caution
    7. 10.7 Glossary
  11. 11Mechanical, 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

Buck Inductor (LO)

Use Equation 10 and Equation 11 to calculate the inductor ripple current (assuming CCM operation) and peak inductor current, respectively.

Equation 10. GUID-C2C08609-D757-4749-BCA9-1EDE62B5E038-low.gif
Equation 11. GUID-96CF319E-C512-46DA-A7C7-9F66FB1DA468-low.gif

For most applications, choose an inductance such that the inductor ripple current, ΔIL, is between 30% and 50% of the rated load current at nominal input voltage. Use Equation 12 to calculate the inductance.

Equation 12. GUID-D227E94D-2161-4CB8-87CC-DD4804EF7A9E-low.gif

For applications in which the device must support input transients exceeding 72 V, select the inductor to be at least 22 μH, which ensures that excessive current rise does not occur in the power stage due to the potential large inductor current slew that can occur in an output short-circuit condition.

Choosing a 22-μH inductor in this design results in 1.36-A peak-to-peak ripple current at a nominal input voltage of 48 V, equivalent to 39% of the 3.5-A rated load current. For designs which must operate up to the maximum input voltage at the full-rated load current of 3.5 A, the inductance needs to increase to ensure current limit (IPEAK current limit) is not hit.

Check the inductor data sheet to make sure the saturation current of the inductor is well above the current limit setting of the LM5013. TI recommends a saturation current greater than 7 A. Ferrite-core inductors have relatively lower core losses and are preferred at high switching frequencies, but exhibit a hard saturation characteristic – the inductance collapses abruptly when the saturation current is exceeded. This collapse results in an abrupt increase in inductor ripple current, higher output voltage ripple, and reduced efficiency, and in turn compromising reliability. Note that inductor saturation current levels generally decrease as the core temperature increases.