SNVS600J December   2008  – June 2022 LM5088 , LM5088-Q1

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings: LM5088
    3. 6.3 ESD Ratings: LM5088-Q1
    4. 6.4 Recommended Operating Conditions
    5. 6.5 Thermal Information
    6. 6.6 Electrical 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 Low-Dropout Regulator
      2. 7.3.2  Line Undervoltage Detector
      3. 7.3.3  Oscillator and Sync Capability
      4. 7.3.4  Error Amplifier and PWM Comparator
      5. 7.3.5  Ramp Generator
      6. 7.3.6  Dropout Voltage Reduction
      7. 7.3.7  Frequency Dithering (LM5088-1 Only)
      8. 7.3.8  Cycle-by-Cycle Current Limit
      9. 7.3.9  Overload Protection Timer (LM5088-2 Only)
      10. 7.3.10 Soft Start
      11. 7.3.11 HG Output
      12. 7.3.12 Thermal Protection
    4. 7.4 Device Functional Modes
      1. 7.4.1 EN Pin Modes
  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  Timing Resistor
        2. 8.2.2.2  Output Inductor
        3. 8.2.2.3  Current Sense Resistor
        4. 8.2.2.4  Ramp Capacitor
        5. 8.2.2.5  Output Capacitors
        6. 8.2.2.6  Input Capacitors
        7. 8.2.2.7  VCC Capacitor
        8. 8.2.2.8  Bootstrap Capacitor
        9. 8.2.2.9  Soft-Start Capacitor
        10. 8.2.2.10 Output Voltage Divider
        11. 8.2.2.11 UVLO Divider
        12. 8.2.2.12 Restart Capacitor (LM5008-2 Only)
        13. 8.2.2.13 MOSFET Selection
        14. 8.2.2.14 Diode Selection
        15. 8.2.2.15 Snubber Components Selection
        16. 8.2.2.16 Error Amplifier Compensation
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
    1. 9.1 Thermal Considerations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Receiving Notification of Documentation Updates
    2. 11.2 Support Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

8.2.2.9 Soft-Start Capacitor

The capacitor at the SS capacitor determines the soft-start time, the output voltage to reach the final regulated value. The value of CSS for a given time is determined from:

Equation 19. GUID-4F957F8F-B2B8-4B92-9AC2-38753A093D21-low.gif

For this design example, a value of 0.022 µF was chosen for a soft-start time of approximately 2 ms.