JAJSGX1G September   2006  – Jaunuary 2020 LM5069

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の図
  4. 4 改訂履歴
    1.     Device Comparison
  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 Current Limit
      2. 7.3.2 Circuit Breaker
      3. 7.3.3 Power Limit
      4. 7.3.4 Undervoltage Lockout (UVLO)
      5. 7.3.5 Overvoltage Lockout (OVLO)
      6. 7.3.6 Power Good Pin
    4. 7.4 Device Functional Modes
      1. 7.4.1 Power Up Sequence
      2. 7.4.2 Gate Control
      3. 7.4.3 Fault Timer and Restart
      4. 7.4.4 Shutdown Control
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 48-V, 10-A Hot Swap Design
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Select RSNS and CL setting
          2. 8.2.1.2.2 Selecting the Hot Swap FET(s)
          3. 8.2.1.2.3 Select Power Limit
          4. 8.2.1.2.4 Set Fault Timer
          5. 8.2.1.2.5 Check MOSFET SOA
          6. 8.2.1.2.6 Set Undervoltage and Overvoltage Threshold
            1. 8.2.1.2.6.1 Option A
            2. 8.2.1.2.6.2 Option B
            3. 8.2.1.2.6.3 Option C
            4. 8.2.1.2.6.4 Option D
          7. 8.2.1.2.7 Input and Output Protection
          8. 8.2.1.2.8 Final Schematic and Component Values
        3. 8.2.1.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 PC Board Guidelines
      2. 10.1.2 System Considerations
    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 デバイス・サポート
      1. 11.1.1 開発サポート
    2. 11.2 ドキュメントのサポート
      1. 11.2.1 関連資料
    3. 11.3 ドキュメントの更新通知を受け取る方法
    4. 11.4 コミュニティ・リソース
    5. 11.5 商標
    6. 11.6 静電気放電に関する注意事項
    7. 11.7 Glossary
  12. 12メカニカル、パッケージ、および注文情報

8.2.1.2.4 Set Fault Timer

The fault timer runs when the hot swap is in power limit or current limit, which is the case during start-up. Thus the timer has to be sized large enough to prevent a time-out during start-up. If the part starts directly into current limit (ILIM × VDS < PLIM) the maximum start time can be computed with Equation 11.

Equation 11. LM5069 Equation11_SNVS452.gif

For most designs (including this example), ILIM × VDS > PLIM, so the hot swap starts in power limit and transition into current limit. In that case, the estimated start time can be computed with Equation 12.

Equation 12. LM5069 Equation12_SNVS452.gif

Note that the above start-time assumes constant, typical current limit and power limit values. The actual startup time is slightly longer, as the power limit is a function of Vds and decreases as the output voltage increases. To ensure that the timer never times out during start-up, TI recommends setting the minimum fault time (tflt) to be greater than the start time (tstart) by adding an additional margin of 50% of the fault time. This accounts for the variation in power limit, timer current, and timer capacitance. Thus CTIMER can be computed with Equation 13.

Equation 13. LM5069 eq_24_sn452.gif

The next largest available CTIMER is chosen as 150 nf. Once the CTIMER is chosen the actual programmed fault time can be computed with Equation 14.

Equation 14. LM5069 Equation13_SNVS452.gif

This is the typical time that the LM5069 shuts off the CSD19536KTT MOSFET.