SNVS485I June   2007  – September 2018 LM2735

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Typical Boost Application Circuit
      2.      Efficiency vs Load Current VO = 12 V
  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: LM2735
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
      1. 7.1.1 Theory of Operation
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Current Limit
      2. 7.3.2 Thermal Shutdown
      3. 7.3.3 Soft Start
      4. 7.3.4 Compensation
    4. 7.4 Device Functional Modes
      1. 7.4.1 Enable Pin and Shutdown Mode
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1  LM2735X SOT-23 Design Example 1
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Custom Design With WEBENCH® Tools
          2. 8.2.1.2.2 Inductor Selection
          3. 8.2.1.2.3 Input Capacitor
          4. 8.2.1.2.4 Output Capacitor
          5. 8.2.1.2.5 Setting the Output Voltage
        3. 8.2.1.3 Application Curves
      2. 8.2.2  LM2735Y SOT-23 Design Example 2
      3. 8.2.3  LM2735X WSON Design Example 3
      4. 8.2.4  LM2735Y WSON Design Example 4
      5. 8.2.5  LM2735Y MSOP-PowerPAD Design Example 5
      6. 8.2.6  LM2735X SOT-23 Design Example 6
      7. 8.2.7  LM2735Y SOT-23 Design Example 7
      8. 8.2.8  LM2735X SOT-23 Design Example 8
      9. 8.2.9  LM2735Y SOT-23 Design Example 9
      10. 8.2.10 LM2735X WSON Design Example 10
      11. 8.2.11 LM2735Y WSON Design Example 11
      12. 8.2.12 LM2735X WSON SEPIC Design Example 12
      13. 8.2.13 LM2735Y MSOP-PowerPAD SEPIC Design Example 13
      14. 8.2.14 LM2735X SOT-23 LED Design Example 14
      15. 8.2.15 LM2735Y WSON FlyBack Design Example 15
      16. 8.2.16 LM2735X SOT-23 LED Design Example 16 VRAIL > 5.5 V Application
      17. 8.2.17 LM2735X SOT-23 LED Design Example 17 Two-Input Voltage Rail Application
      18. 8.2.18 SEPIC Converter
        1. 8.2.18.1 Detailed Design Procedure
          1. 8.2.18.1.1 SEPIC Design Guide
          2. 8.2.18.1.2 Small Ripple Approximation
          3. 8.2.18.1.3 Steady State Analysis With Loss Elements
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 WSON Package
    2. 10.2 Layout Examples
    3. 10.3 Thermal Considerations
      1. 10.3.1 Definitions
      2. 10.3.2 PCB Design With Thermal Performance in Mind
      3. 10.3.3 LM2735 Thermal Models
      4. 10.3.4 Calculating Efficiency, and Junction Temperature
        1. 10.3.4.1 Example Efficiency Calculation
      5. 10.3.5 Calculating RθJA and RΨJC
        1. 10.3.5.1 Procedure
        2. 10.3.5.2 Example From Previous Calculations
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
      2. 11.1.2 Development Support
        1. 11.1.2.1 Custom Design With WEBENCH® Tools
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    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

8.2.1.2.4 Output Capacitor

The LM2735 operates at frequencies allowing the use of ceramic output capacitors without compromising transient response. Ceramic capacitors allow higher inductor ripple without significantly increasing output ripple. The output capacitor is selected based upon the desired output ripple and transient response. The initial current of a load transient is provided mainly by the output capacitor. The output impedance will therefore determine the maximum voltage perturbation. The output ripple of the converter is a function of the reactance of the capacitor and its equivalent series resistance (ESR):

Equation 15. LM2735 20215828.gif

When using MLCCs, the ESR is typically so low that the capacitive ripple may dominate. When this occurs, the output ripple will be approximately sinusoidal and 90° phase shifted from the switching action.

Given the availability and quality of MLCCs and the expected output voltage of designs using the LM2735, there is really no need to review any other capacitor technologies. Another benefit of ceramic capacitors is their ability to bypass high-frequency noise. A certain amount of switching edge noise will couple through parasitic capacitances in the inductor to the output. A ceramic capacitor will bypass this noise while a tantalum will not. Since the output capacitor is one of the two external components that control the stability of the regulator control loop, most applications will require a minimum at 4.7 µF of output capacitance. Like the input capacitor, recommended multilayer ceramic capacitors are X7R or X5R. Again, verify actual capacitance at the desired operating voltage and temperature.