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

10.3.4.1 Example Efficiency Calculation

Table 3. Operating Conditions

PARAMETER VALUE
VIN 5 V
VOUT 12 V
IOUT 500 mA
VD 0.4 V
FSW 1.60 MHz
IQ 4 mA
TRISE 6 nS
TFALL 5 nS
RDSon 250 mΩ
RDCR 50 mΩ
D 0.64
IIN 1.4 A
Equation 48. ΣPCOND + PSW + PDIODE + PIND + PQ = PLOSS

Quiescent Power Losses:

Equation 49. PQ = IQ × VIN = 20 mW

Switching Power Losses:

Equation 50. PSWR = 1/2(VOUT × IIN × FSW × TRISE) ≊ 6 ns ≊ 80 mW
Equation 51. PSWF = 1/2(VOUT × IIN × FSW × TFALL) ≊ 5 ns ≊ 70 mW
Equation 52. PSW = PSWR + PSWF = 150 mW

Internal NFET Power Losses:

Equation 53. RDSON = 250 mΩ
Equation 54. PCONDUCTION = IIN2 × D × RDSON × 305 mW

Diode Losses:

Equation 55. VD = 0.45 V
Equation 56. PDIODE = VD × IIN(1–D) = 236 mW

Inductor Power Losses:

Equation 57. RDCR = 75 mΩ
Equation 58. PIND = IIN2 × RDCR = 145 mW

Total Power Losses are:

Table 4. Power Loss Tabulation

PARAMETER VALUE PARAMETER VALUE
VIN 5 V
VOUT 12 V
IOUT 500 mA POUT 6 W
VD 0.4 V PDIODE 236 mW
FSW 1.6 MHz
TRISE 6 nS PSWR 80 mW
TFALL 5 nS PSWF 70 mW
IQ 4 mA PQ 20 mW
RDSon 250 mΩ PCOND 305 mW
RDCR 75 mΩ PIND 145 mW
D 0.623
η 86% PLOSS 856 mW
Equation 59. PINTERNAL = PCOND + PSW = 475 mW