ZHCSIT5B september   2018  – august 2023 LM5164

PRODUCTION DATA  

  1.   1
  2. 1 特性
  3. 2 应用
  4. 3 说明
  5. 4 Revision History
  6. 5 Pin Configuration and Functions
  7. 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
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Control Architecture
      2. 7.3.2  Internal VCC Regulator and Bootstrap Capacitor
      3. 7.3.3  Regulation Comparator
      4. 7.3.4  Internal Soft Start
      5. 7.3.5  On-Time Generator
      6. 7.3.6  Current Limit
      7. 7.3.7  N-Channel Buck Switch and Driver
      8. 7.3.8  Synchronous Rectifier
      9. 7.3.9  Enable/Undervoltage Lockout (EN/UVLO)
      10. 7.3.10 Power Good (PGOOD)
      11. 7.3.11 Thermal Protection
    4. 7.4 Device Functional Modes
      1. 7.4.1 Shutdown Mode
      2. 7.4.2 Active Mode
      3. 7.4.3 Sleep Mode
  9. 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 Custom Design With WEBENCH® Tools
        2. 8.2.2.2 Switching Frequency (RRON)
        3. 8.2.2.3 Buck Inductor (LO)
        4. 8.2.2.4 Output Capacitor (COUT)
        5. 8.2.2.5 Input Capacitor (CIN)
        6. 8.2.2.6 Type-3 Ripple Network
      3. 8.2.3 Application Curves
  10. 9 Power Supply Recommendations
  11. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 Compact PCB Layout for EMI Reduction
      2. 10.1.2 Feedback Resistors
    2. 10.2 Layout Example
  12. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 第三方产品免责声明
      2. 11.1.2 Development Support
        1. 11.1.2.1 Custom Design With WEBENCH® Tools
    2. 11.2 Related Documentation
    3. 11.3 接收文档更新通知
    4. 11.4 支持资源
    5. 11.5 Trademarks
    6. 11.6 静电放电警告
    7. 11.7 术语表
  13. 12Mechanical, Packaging, and Orderable Information

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7.3.6 Current Limit

The LM5164 manages overcurrent conditions with cycle-by-cycle current limiting of the peak inductor current. The current sensed in the high-side MOSFET is compared every switching cycle to the current limit threshold (1.5 A). To protect the converter from potential current runaway conditions, the LM5164 includes a foldback valley current limit feature, set at 1.2 A, that is enabled if a peak current limit is detected. As shown in Figure 7-1, if the peak current in the high-side MOSFET exceeds 1.5 A (typical), the present cycle is immediately terminated regardless of the programmed on-time (tON), the high-side MOSFET is turned off and the foldback valley current limit is activated. The low-side MOSFET remains on until the inductor current drops below this foldback valley current limit, after which the next on-pulse is initiated. This method folds back the switching frequency to prevent overheating and limits the average output current to less than 1.5 A to ensure proper short-circuit and heavy-load protection of the LM5164.

GUID-25D35CA9-3095-4F98-BF89-56B1B8FE6E0E-low.gifFigure 7-1 Current Limit Timing Diagram

Current is sensed after a leading-edge blanking time following the high-side MOSFET turnon transition. The propagation delay of the current limit comparator is 100 ns. During high step-down conditions when the on-time is less than 100 ns, a back-up peak current limit comparator in the low-side FET also set at 1.5 A enables the foldback valley current limit set at 1.2 A. This innovative current limit scheme enables ultra-low duty-cycle operation, permitting large step-down voltage conversions while ensuring robust protection of the converter.