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

7.3.9 Current Sense

There are two methods to sense the inductor current of the buck converter. The first is using current sense resistor in series with the inductor and the second is to use the dc resistance of the inductor (DCR sensing). Figure 24 illustrates inductor current sensing using a current sense resistor. This configuration continuously monitors the inductor current providing accurate current-limit protection. For the best current-sense accuracy and over current protection, use a low inductance ±1% tolerance current-sense resistor between the inductor and output, with a Kelvin connection to the LM5141 sense amplifier.

If the peak differential current signal sensed from CS to VOUT exceeds 75 mV, the current limit comparator immediately terminates the HO output for cycle-by-cycle current limiting.

Equation 11. LM25141 equation_10_snvsaj6.gif

where

  • V(CS) = 75 mV

IOUT(MAX) is the over current set point which is set higher than the maximum load current to avoid tripping the over current comparator during load transients. ΔI is the peak-peak inductor ripple current.

LM25141 current_sense_snvsaj6.gifFigure 24. Current Sense