JAJSAY1E March   2008  – October 2017 LM2854

PRODUCTION DATA.  

  1. 1 特長
  2. 2 アプリケーション
  3. 3 概要
    1.     Device Images
      1.      代表的なアプリケーション回路
  4. 4 改訂履歴
  5. 5 Pin Configuration and Functions
    1.     Pin 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 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  Switching Frequency
      2. 7.3.2  Enable
      3. 7.3.3  Soft-Start
      4. 7.3.4  Tracking
      5. 7.3.5  Pre-Biased Start-up Capability
      6. 7.3.6  Feedback Voltage Accuracy
      7. 7.3.7  Positive Current Limit
      8. 7.3.8  Negative Current Limit
      9. 7.3.9  Overtemperature Protection
      10. 7.3.10 Loop Compensation
    4. 7.4 Device Functional Modes
      1. 7.4.1 Shutdown Mode
      2. 7.4.2 Soft-Start and Track Mode
      3. 7.4.3 Normal Operating Mode
  8. 8 Application 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 Input Filter Capacitor
        2. 8.2.2.2 AVIN Filtering Components
        3. 8.2.2.3 Soft-Start Capacitor
        4. 8.2.2.4 Tracking - Equal Soft-Start Time
        5. 8.2.2.5 Tracking - Equal Slew Rates
        6. 8.2.2.6 Enable and UVLO
        7. 8.2.2.7 Output Voltage Setting
        8. 8.2.2.8 Compensation Component Selection
        9. 8.2.2.9 Filter Inductor and Output Capacitor Selection
      3. 8.2.3 Application Curves
      4. 8.2.4 System Examples
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11デバイスおよびドキュメントのサポート
    1. 11.1 ドキュメントのサポート
      1. 11.1.1 関連資料
    2. 11.2 商標
    3. 11.3 静電気放電に関する注意事項
    4. 11.4 Glossary
  12. 12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

7.3.5 Pre-Biased Start-up Capability

The LM2854 is in a pre-biased state when the device starts up with an output voltage greater than zero. This often occurs in many multi-rail applications such as when powering an FPGA, ASIC, or DSP. The output can be pre-biased in these applications through parasitic conduction paths from one supply rail to another. Even though the LM2854 is a synchronous converter, it will not pull the output low when a pre-bias condition exists. The LM2854 will not sink current during start up until the soft-start voltage exceeds the voltage on the FB pin. Since the device can not sink current it protects the load from damage that might otherwise occur if current is conducted through the parasitic paths of the load.