SNOSB23F October   2008  – July 2019 LM5575-Q1

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Simplified Schematic
  4. 4 Revision History
  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 Shutdown and Standby
      2. 7.3.2 Current Limit
      3. 7.3.3 Soft Start
      4. 7.3.4 Thermal Protection
    4. 7.4 Device Functional Modes
      1. 7.4.1 High-Voltage Start-Up Regulator
      2. 7.4.2 Oscillator and Sync Capability
      3. 7.4.3 Error Amplifier and PWM Comparator
      4. 7.4.4 Ramp Generator
      5. 7.4.5 BOOST Pin
      6. 7.4.6 Maximum Duty Cycle and Input Dropout Voltage
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Bias Power Dissipation Reduction
    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  External Components
        3. 8.2.2.3  R3 (RT)
        4. 8.2.2.4  L1
        5. 8.2.2.5  C3 (CRAMP)
        6. 8.2.2.6  C9, C10
        7. 8.2.2.7  D1
        8. 8.2.2.8  C1, C2
        9. 8.2.2.9  C8
        10. 8.2.2.10 C7
        11. 8.2.2.11 C4
        12. 8.2.2.12 R5, R6
        13. 8.2.2.13 R1, R2, C12
        14. 8.2.2.14 R7, C11
        15. 8.2.2.15 R4, C5, C6
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Examples
    3. 10.3 Thermal Considerations
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Custom Design With WEBENCH® Tools
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Community Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

7.3.2 Current Limit

The LM5575-Q1 contains a unique current monitoring scheme for control and overcurrent protection. When set correctly, the emulated current sense signal provides a signal which is proportional to the buck switch current with a scale factor of 1 V/A. The emulated ramp signal is applied to the current limit comparator. If the emulated ramp signal exceeds 2.1 V (2.1 A), the present current cycle is terminated (cycle-by-cycle current limiting). In applications with small output inductance and high-input voltage, the switch current may overshoot due to the propagation delay of the current limit comparator. If an overshoot should occur, the diode current sampling circuit will detect the excess inductor current during the off-time of the buck switch. If the sample and hold DC level exceeds the 2.1-V current limit threshold, the buck switch will be disabled and skip pulses until the diode current sampling circuit detects the inductor current has decayed below the current limit threshold. This approach prevents current runaway conditions due to propagation delays or inductor saturation because the inductor current is forced to decay following the current overshoot.