SNVSCL2 December   2024 LM51770

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison
  6. 5 Pin Configuration and Functions
  7. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 Handling Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Typical Characteristics
  8. 7 Parameter Measurement Information
    1. 7.1 Gate Driver Rise Time and Fall Time
    2. 7.2 Gate Driver Dead (Transition) Time
  9. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1  Power-On Reset (POR System)
      2. 8.3.2  Buck-Boost Control Scheme
        1. 8.3.2.1 Boost Mode
        2. 8.3.2.2 Buck Mode
        3. 8.3.2.3 Buck-Boost Mode
      3. 8.3.3  Power Save Mode
      4. 8.3.4  Supply Voltage Selection – VMAX Switch
      5. 8.3.5  Enable and Undervoltage Lockout
      6. 8.3.6  Oscillator Frequency Selection
      7. 8.3.7  Frequency Synchronization
      8. 8.3.8  Voltage Regulation Loop
      9. 8.3.9  Output Voltage Tracking
      10. 8.3.10 Slope Compensation
      11. 8.3.11 Configurable Soft Start
      12. 8.3.12 Peak Current Sensor
      13. 8.3.13 Current Monitoring and Current Limit Control Loop
      14. 8.3.14 Short Circuit - Hiccup Protection
      15. 8.3.15 nFLT Pin and Protections
      16. 8.3.16 Device Configuration Pin
      17. 8.3.17 Dual Random Spread Spectrum – DRSS
      18. 8.3.18 Gate Driver
    4. 8.4 Device Functional Modes
  10. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Detailed Design Procedure
        1. 9.2.1.1  Custom Design with WEBENCH Tools
        2. 9.2.1.2  Frequency
        3. 9.2.1.3  Feedback Divider
        4. 9.2.1.4  Inductor and Current Sense Resistor Selection
        5. 9.2.1.5  Slope Compensation
        6. 9.2.1.6  Output Capacitor
        7. 9.2.1.7  Input Capacitor
        8. 9.2.1.8  UVLO Divider
        9. 9.2.1.9  Soft-Start Capacitor
        10. 9.2.1.10 MOSFETs QH1 and QL1
        11. 9.2.1.11 MOSFETs QH2 and QL2
        12. 9.2.1.12 Frequency Compensation
        13. 9.2.1.13 External Component Selection
      2. 9.2.2 Application Curves
  11. 10Power Supply Recommendations
  12. 11Layout
    1. 11.1 Layout Guidelines
      1. 11.1.1 Power Stage Layout
      2. 11.1.2 Gate Driver Layout
      3. 11.1.3 Controller Layout
    2. 11.2 Layout Example
  13. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Third-Party Products Disclaimer
      2. 12.1.2 Development Support
        1. 12.1.2.1 Custom Design with WEBENCH Tools
    2. 12.2 Receiving Notification of Documentation Updates
    3. 12.3 Support Resources
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 Glossary
  14. 13Revision History
  15. 14Mechanical, Packaging, and Orderable Information
    1.     80

Package Options

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

11.1.3 Controller Layout

With the provision to locate the controller as close as possible to the power MOSFETs to minimize gate driver trace runs, the components related to the analog and feedback signals as well as current sensing are considered in the following:

  • Separate power and signal traces, and use a ground plane to provide noise shielding.
  • Place all sensitive analog traces and components related to COMP, FB, SLOPE, SS/ATRK, and RT away from high-voltage switching nodes such as the following to avoid mutual coupling:
    • SW1
    • SW2
    • HO1
    • HO2
    • LO1
    • LO2
    • HB1
    • HB2
  • Use an internal layer or layers as ground plane or planes. Pay particular attention to shielding the feedback (FB) trace from power traces and components.
  • Route the CSA and CSB and ISNSP and ISNSN traces as differential pairs to minimize noise pickup and use Kelvin connections to the applicable shunt resistor.
  • Locate the upper and lower feedback resistors close to the FB pins, keeping the FB traces as short as possible. Route the trace from the upper feedback resistor or resistors to the output voltage sense point.
  • Use a common ground node for power ground and a different one for analog ground to minimize the effects of ground noise. Connect these ground nodes at any place close to one of the ground pins of the IC.
  • The HTSSOP package offers a means of removing heat from the semiconductor die through the exposed thermal pad at the base of the package. While the exposed pad of the package is not directly connected to any leads of the package, it is thermally connected to the substrate (ground) of the device. This connection allows a significant improvement in heat sinking, and it becomes imperative that the PCB is designed with thermal lands, thermal vias, and a ground plane to complete the heat removal subsystem.