SNVSBI6 January   2021 LM5156 , LM51561

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Description (continued)
  6. 6 Device Comparison Table
  7. 7 Pin Configuration and Functions
  8. 8 Specifications
    1. 8.1 Absolute Maximum Ratings
    2. 8.2 ESD Ratings
    3. 8.3 Recommended Operating Conditions
    4. 8.4 Thermal Information
    5. 8.5 Electrical Characteristics
    6. 8.6 Typical Characteristics
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1  Line Undervoltage Lockout (UVLO/SYNC/EN Pin)
      2. 9.3.2  High Voltage VCC Regulator (BIAS, VCC Pin)
      3. 9.3.3  Soft Start (SS Pin)
      4. 9.3.4  Switching Frequency (RT Pin)
      5. 9.3.5  Dual Random Spread Spectrum (DRSS)
      6. 9.3.6  Clock Synchronization (UVLO/SYNC/EN Pin)
      7. 9.3.7  Current Sense and Slope Compensation (CS Pin)
      8. 9.3.8  Current Limit and Minimum On-time (CS Pin)
      9. 9.3.9  Feedback and Error Amplifier (FB, COMP Pin)
      10. 9.3.10 Power-Good Indicator (PGOOD pin)
      11. 9.3.11 Hiccup Mode Overload Protection (LM51561 Only)
      12. 9.3.12 Maximum Duty Cycle Limit and Minimum Input Supply Voltage
      13. 9.3.13 MOSFET Driver (GATE Pin)
      14. 9.3.14 Overvoltage Protection (OVP)
      15. 9.3.15 Thermal Shutdown (TSD)
    4. 9.4 Device Functional Modes
      1. 9.4.1 Shutdown Mode
      2. 9.4.2 Standby Mode
      3. 9.4.3 Run Mode
  10. 10Application and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
        1. 10.2.2.1 Custom Design With WEBENCH® Tools
        2. 10.2.2.2 Recommended Components
        3. 10.2.2.3 Inductor Selection (LM)
        4. 10.2.2.4 Output Capacitor (COUT)
        5. 10.2.2.5 Input Capacitor
        6. 10.2.2.6 MOSFET Selection
        7. 10.2.2.7 Diode Selection
        8. 10.2.2.8 Efficiency Estimation
      3. 10.2.3 Application Curve
    3. 10.3 System Examples
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Examples
  13. 13Device and Documentation Support
    1. 13.1 Device Support
      1. 13.1.1 Third-Party Products Disclaimer
      2. 13.1.2 Development Support
        1. 13.1.2.1 Custom Design With WEBENCH® Tools
    2. 13.2 Documentation Support
      1. 13.2.1 Related Documentation
    3. 13.3 Receiving Notification of Documentation Updates
    4. 13.4 Support Resources
    5. 13.5 Trademarks
    6. 13.6 Electrostatic Discharge Caution
    7. 13.7 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

Package Options

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

9.3.12 Maximum Duty Cycle Limit and Minimum Input Supply Voltage

When designing boost converters, the maximum duty cycle should be reviewed at the minimum supply voltage. The minimum input supply voltage that can achieve the target output voltage is limited by the maximum duty cycle limit, and it can be estimated as follows.

Equation 15. GUID-86DA2761-3E17-4EA5-A2A1-041DBFFCE196-low.gif

where

  • ISUPPLY(MAX) is the maximum input current
  • RDCR is the DC resistance of the inductor
  • RDS(ON) is the on-resistance of the MOSFET
Equation 16. GUID-CB7BA94A-613F-4231-B79C-6557D6871E67-low.gif
Equation 17. GUID-C9140116-345B-41DA-A228-7C997F0BF7A7-low.gif

The minimum input supply voltage can be further decreased by supplying fSYNC, which is less than fRT. DMAX is DMAX1 or DMAX2, whichever is lower.