SNVSB29C October   2018  – June 2021 LM5143-Q1

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Description (continued)
  6. 6 Pin Configuration and Functions
    1. 6.1 Wettable Flanks
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Switching Characteristics
    7. 7.7 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1  Input Voltage Range (VIN)
      2. 8.3.2  High-Voltage Bias Supply Regulator (VCC, VCCX, VDDA)
      3. 8.3.3  Enable (EN1, EN2)
      4. 8.3.4  Power Good Monitor (PG1, PG2)
      5. 8.3.5  Switching Frequency (RT)
      6. 8.3.6  Clock Synchronization (DEMB)
      7. 8.3.7  Synchronization Out (SYNCOUT)
      8. 8.3.8  Spread Spectrum Frequency Modulation (DITH)
      9. 8.3.9  Configurable Soft Start (SS1, SS2)
      10. 8.3.10 Output Voltage Setpoint (FB1, FB2)
      11. 8.3.11 Minimum Controllable On-Time
      12. 8.3.12 Error Amplifier and PWM Comparator (FB1, FB2, COMP1, COMP2)
      13. 8.3.13 Slope Compensation
      14. 8.3.14 Inductor Current Sense (CS1, VOUT1, CS2, VOUT2)
        1. 8.3.14.1 Shunt Current Sensing
        2. 8.3.14.2 Inductor DCR Current Sensing
      15. 8.3.15 Hiccup Mode Current Limiting (RES)
      16. 8.3.16 High-Side and Low-Side Gate Drivers (HO1/2, LO1/2, HOL1/2, LOL1/2)
      17. 8.3.17 Output Configurations (MODE, FB2)
        1. 8.3.17.1 Independent Dual-Output Operation
        2. 8.3.17.2 Single-Output Interleaved Operation
        3. 8.3.17.3 Single-Output Multiphase Operation
    4. 8.4 Device Functional Modes
      1. 8.4.1 Standby Modes
      2. 8.4.2 Diode Emulation Mode
      3. 8.4.3 Thermal Shutdown
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Power Train Components
        1. 9.1.1.1 Buck Inductor
        2. 9.1.1.2 Output Capacitors
        3. 9.1.1.3 Input Capacitors
        4. 9.1.1.4 Power MOSFETs
        5. 9.1.1.5 EMI Filter
      2. 9.1.2 Error Amplifier and Compensation
    2. 9.2 Typical Applications
      1. 9.2.1 Design 1 – High Efficiency, Dual-Output Buck Regulator for Automotive Applications
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
          1. 9.2.1.2.1 Custom Design With WEBENCH® Tools
          2. 9.2.1.2.2 Custom Design With Excel Quickstart Tool
          3. 9.2.1.2.3 Inductor Calculation
          4. 9.2.1.2.4 Current-Sense Resistance
          5. 9.2.1.2.5 Output Capacitors
          6. 9.2.1.2.6 Input Capacitors
          7. 9.2.1.2.7 Compensation Components
        3. 9.2.1.3 Application Curves
      2. 9.2.2 Design 2 – Two-Phase, Single-Output Buck Regulator for Automotive ADAS Applications
        1. 9.2.2.1 Design Requirements
        2. 9.2.2.2 Detailed Design Procedures
        3. 9.2.2.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
      1. 11.1.1 Power Stage Layout
      2. 11.1.2 Gate-Drive Layout
      3. 11.1.3 PWM Controller Layout
      4. 11.1.4 Thermal Design and Layout
      5. 11.1.5 Ground Plane Design
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Third-Party Products Disclaimer
      2. 12.1.2 Development Support
      3. 12.1.3 Custom Design With WEBENCH® Tools
    2. 12.2 Documentation Support
      1. 12.2.1 Related Documentation
        1. 12.2.1.1 PCB Layout Resources
        2. 12.2.1.2 Thermal Design Resources
    3. 12.3 Receiving Notification of Documentation Updates
    4. 12.4 Support Resources
    5. 12.5 Trademarks
    6. 12.6 Electrostatic Discharge Caution
    7. 12.7 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

8.3.11 Minimum Controllable On-Time

There are two limitations to the minimum output voltage adjustment range: the LM5143-Q1 voltage reference of 0.6 V and the minimum controllable switch-node pulse width, tON(min).

tON(min) effectively limits the voltage step-down conversion ratio of VOUT/VIN at a given switching frequency. For fixed-frequency PWM operation, the voltage conversion ratio must satisfy Equation 8.

Equation 8. GUID-69B984F4-4CE4-4D8D-A63E-374F9E41DB15-low.gif

where

  • tON(min) is 65 ns (typical)
  • FSW is the switching frequency

If the desired voltage conversion ratio does not meet the above condition, the LM5143-Q1 transitions from fixed switching frequency operation to a pulse-skipping mode to maintain output voltage regulation. For example, if the desired output voltage is 5 V with an input voltage is 24 V and switching frequency of 2.1 MHz, the voltage conversion ratio test in Equation 9 is satisfied.

Equation 9. GUID-39B84C73-6546-44C9-BE17-E151FC305436-low.gif

For wide VIN applications and low output voltages, an alternative is to reduce the LM5143-Q1 switching frequency to meet the requirement of Equation 8.