JAJSGM5 December   2018 TPS54340B

PRODUCTION DATA.  

  1. 1 特長
  2. 2 アプリケーション
  3. 3 概要
    1.     Device Images
      1.      概略回路図
      2.      効率と負荷電流との関係
  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  Fixed Frequency PWM Control
      2. 8.3.2  Slope Compensation Output Current
      3. 8.3.3  Pulse Skip Eco-mode
      4. 8.3.4  Low Dropout Operation and Bootstrap Voltage (BOOT)
      5. 8.3.5  Error Amplifier
      6. 8.3.6  Adjusting the Output Voltage
      7. 8.3.7  Enable and Adjusting Undervoltage Lockout
      8. 8.3.8  Internal Soft Start
      9. 8.3.9  Constant Switching Frequency and Timing Resistor (RT/CLK) pin)
      10. 8.3.10 Accurate Current Limit Operation and Maximum Switching Frequency
      11. 8.3.11 Synchronization to RT/CLK pin
      12. 8.3.12 Overvoltage Protection
      13. 8.3.13 Thermal Shutdown
      14. 8.3.14 Small Signal Model for Loop Response
      15. 8.3.15 Simple Small Signal Model for Peak-Current-Mode Control
      16. 8.3.16 Small Signal Model for Frequency Compensation
    4. 8.4 Device Functional Modes
      1. 8.4.1 Operation with VIN ≤ 4.5 V (Minimum VIN)
      2. 8.4.2 Operation with EN Control
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application: Buck Converter
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedures
        1. 9.2.2.1  Custom Design with WEBENCH® Tools
        2. 9.2.2.2  Selecting the Switching Frequency
        3. 9.2.2.3  Output Inductor Selection (LO)
        4. 9.2.2.4  Output Capacitor
        5. 9.2.2.5  Catch Diode
        6. 9.2.2.6  Input Capacitor
        7. 9.2.2.7  Bootstrap Capacitor Selection
        8. 9.2.2.8  Undervoltage Lockout Setpoint
        9. 9.2.2.9  Output Voltage and Feedback Resistors Selection
        10. 9.2.2.10 Minimum VIN
        11. 9.2.2.11 Compensation
        12. 9.2.2.12 Discontinuous Conduction Mode and Eco-mode Boundary
        13. 9.2.2.13 Power Dissipation
      3. 9.2.3 Application Curves
    3. 9.3 Other Applications
      1. 9.3.1 Inverting Power
      2. 9.3.2 Split-Rail Power Supply
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
      1. 11.2.1 Estimated Circuit Area
  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 WEBENCH®ツールによるカスタム設計
    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
  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

9.2.2.8 Undervoltage Lockout Setpoint

The undervoltage lockout (UVLO) can be adjusted using an external voltage divider on the EN terminal of the TPS54340. The UVLO has two thresholds, one for power up when the input voltage is rising and one for power down or brownouts when the input voltage is falling. For the example design, the supply must turn on and start switching once the input voltage increases above 5.75 V (UVLO start). After the regulator starts switching, it should continue to do so until the input voltage falls below 4.5 V (UVLO stop).

Programmable UVLO threshold voltages are set using the resistor divider of RUVLO1 and RUVLO2 between VIN and ground connected to the EN terminal. Equation 4 and Equation 5 calculate the resistance values necessary. For the example application, a 365 kΩ between VIN and EN (RUVLO1) and a 86.6 kΩ between EN and ground (RUVLO2) are required to produce the 8-V and 6.25-V start and stop voltages.

Equation 40. TPS54340B q_R1_lvsBK0.gif
Equation 41. TPS54340B q_R2_lvsBK0.gif