SNVSAU1 March   2017 LM25141

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 Switching Characteristics
    7. 6.7 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  High Voltage Start-up Regulator
      2. 7.3.2  VCC Regulator
      3. 7.3.3  Oscillator
      4. 7.3.4  Synchronization
      5. 7.3.5  Frequency Dithering (Spread Spectrum)
      6. 7.3.6  Enable
      7. 7.3.7  Power Good
      8. 7.3.8  Output Voltage
        1. 7.3.8.1 Minimum Output Voltage Adjustment
      9. 7.3.9  Current Sense
      10. 7.3.10 DCR Current Sensing
      11. 7.3.11 Error Amplifier and PWM Comparator
      12. 7.3.12 Slope Compensation
      13. 7.3.13 Hiccup Mode Current Limiting
      14. 7.3.14 Standby Mode
      15. 7.3.15 Soft-Start
      16. 7.3.16 Diode Emulation
      17. 7.3.17 High and Low Side Drivers
  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 Custom Design With WEBENCH® Tools
      3. 8.2.3 Inductor Calculation
      4. 8.2.4 Current Sense Resistor
      5. 8.2.5 Output Capacitor
      6. 8.2.6 Input Filter
        1. 8.2.6.1 EMI Filter Design
        2. 8.2.6.2 MOSFET Selection
        3. 8.2.6.3 Driver Slew Rate Control
        4. 8.2.6.4 Frequency Dithering
      7. 8.2.7 8.9 Control Loop
        1. 8.2.7.1 Feedback Compensator
      8. 8.2.8 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 Layout Procedure
    2. 10.2 Layout Examples
  11. 11Device and Documentation Support
    1. 11.1 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

8.2.6.3 Driver Slew Rate Control

Figure 30 shows the high current driver outputs with independent source and current sink pins for slew rate control. Slew rate control enables the user to adjust the switch node rise and fall times which can reduce the conducted EMI in the FM radio band (30 MHz to 108 MHz). Figure 31 shows the measured results without slew rate control.

The conducted EMI results with slew rate control are shown in Figure 32, a 10-dB reduction in conduction emissions in the FM band is attained by using slew rate control. This can help reduce the size and cost of the EMI filters.

LM25141 drivers_snvsaj6.gifFigure 30. Drivers with Slew Rate Control
LM25141 emi_measurements_cispr_25_class_5_without_slew_rate_control_snvsaj6.pngFigure 31. Conducted EMI Measurement, Without Slew Rate Control
LM25141 emi_measurements_cispr_25_witt_slew_rate_control_snvsaj6.pngFigure 32. Conducted EMI Measurements, With Slew Rate Control