JAJSGD5E October   2014  – October 2018 LM5160 , LM5160A

PRODUCTION DATA.  

  1. 1 特長
  2. 2 アプリケーション
  3. 3 概要
    1.     Device Images
      1.      代表的な同期整流降圧アプリケーション回路
      2.      代表的なFly-Buckアプリケーション回路
  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 Switching Characteristics
    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  Control Circuit
      2. 8.3.2  VCC Regulator
      3. 8.3.3  Regulation Comparator
      4. 8.3.4  Soft Start
      5. 8.3.5  Error Amplifier
      6. 8.3.6  On-Time Generator
      7. 8.3.7  Current Limit
      8. 8.3.8  N-Channel Buck Switch and Driver
      9. 8.3.9  Synchronous Rectifier
      10. 8.3.10 Enable / Undervoltage Lockout (EN/UVLO)
      11. 8.3.11 Thermal Protection
    4. 8.4 Device Functional Modes
      1. 8.4.1 Forced Pulse Width Modulation (FPWM) Mode
      2. 8.4.2 Undervoltage Detector
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Ripple Configuration
    2. 9.2 Typical Applications
      1. 9.2.1 LM5160 Synchronous Buck (10-V to 60-V Input, 5-V Output, 1.5-A Load)
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
          1. 9.2.1.2.1  Custom Design With WEBENCH® Tools
          2. 9.2.1.2.2  Feedback Resistor Divider - RFB1, RFB2
          3. 9.2.1.2.3  Switching Frequency - RON
          4. 9.2.1.2.4  Inductor - L
          5. 9.2.1.2.5  Output Capacitor - COUT
          6. 9.2.1.2.6  Series Ripple Resistor - RESR
          7. 9.2.1.2.7  VCC and Bootstrap Capacitors - CVCC, CBST
          8. 9.2.1.2.8  Input Capacitor - CIN
          9. 9.2.1.2.9  Soft-Start Capacitor - CSS
          10. 9.2.1.2.10 EN/UVLO Resistors - RUV1, RUV2
        3. 9.2.1.3 Application Curves
      2. 9.2.2 LM5160 Isolated Fly-Buck (18-V to 32-V Input, 12-V, 4.5-W Isolated Output)
        1. 9.2.2.1 LM5160 Fly-Buck Design Requirements
        2. 9.2.2.2 Detailed Design Procedure
          1. 9.2.2.2.1 Selection of VOUT1 and Turns Ratio
          2. 9.2.2.2.2 Secondary Rectifier Diode
          3. 9.2.2.2.3 External Ripple Circuit
          4. 9.2.2.2.4 Output Capacitor - COUT2
        3. 9.2.2.3 Application Curves
      3. 9.2.3 LM5160A Isolated Fly-Buck (18-V to 32-V Input, 12-V, 4.5-W Isolated Output)
    3. 9.3 Do's and Don'ts
  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 デバイス・サポート
      1. 12.1.1 デベロッパー・ネットワークの製品に関する免責事項
      2. 12.1.2 開発サポート
        1. 12.1.2.1 WEBENCH®ツールによるカスタム設計
    2. 12.2 ドキュメントのサポート
      1. 12.2.1 関連資料
    3. 12.3 関連リンク
    4. 12.4 ドキュメントの更新通知を受け取る方法
    5. 12.5 コミュニティ・リソース
    6. 12.6 商標
    7. 12.7 静電気放電に関する注意事項
    8. 12.8 Glossary
  13. 13メカニカル、パッケージ、および注文情報

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

9.2.1.2.3 Switching Frequency - RON

The duty cycle required to maintain output regulation at the minimum input voltage restricts the maximum switching frequency of the LM5160. The maximum value of the minimum forced off-time, TOFF,min, limits the duty cycle and therefore the switching frequency. Calculate the maximum frequency that avoids output dropout at minimum input voltage using Equation 10.

Equation 10. LM5160 LM5160A eq07_snvsa03.gif

For this design example, the maximum frequency based on the minimum off-time limitation of TOFF,min (typical) = 170 ns is calculated as FSW,max(@VIN,min) = 2.9 MHz. This value is well above 1 MHz, the maximum possible operating frequency of the LM5160.

At maximum input voltage the maximum switching frequency of the LM5160 is restricted by the minimum on-time, TON,min which limits the minimum duty cycle of the converter. Calculate the maximum frequency at maximum input voltage using Equation 11.

Equation 11. LM5160 LM5160A eq08_snvsa03.gif

Using Equation 11 and TON,min (typical) = 150 ns, the maximum achievable switching frequency is FSW,max(@VIN,min) = 514 kHz. Taking this value as the maximum possible switching frequency over the input voltage range for this application, choose a nominal switching frequency of FSW = 300 kHz for this design. The value of resistor RON sets the nominal switching frequency based on Equation 12.

Equation 12. LM5160 LM5160A eq09_snvsa03.gif

For this particular application with FSW = 300 kHz, RON calculates to be 167 kΩ. Selecting a standard value for R3 (RON) = 169 kΩ (±1%) results in a nominal frequency of 296 kHz. The resistor value may need to adjusted further in order to achieve the required switching frequency as the switching frequency in COT converters varies slightly (±10%) with input voltage and/or output current. Operation at a lower nominal switching frequency results in higher efficiency but increases the inductor and capacitor values leading to a larger total solution size.