SNVS402I February   2006  – May 2021 LM5009

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
    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
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Control Circuit Overview
      2. 7.3.2 High Voltage Startup Regulator
      3. 7.3.3 Regulation Comparator
      4. 7.3.4 Overvoltage Comparator
      5. 7.3.5 On-Time Generator
      6. 7.3.6 Current Limit
      7. 7.3.7 N-Channel Buck Switch and Driver
      8. 7.3.8 Thermal Protection
    4. 7.4 Device Functional 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 Output Resistor Divider Selection
        2. 8.2.2.2 Frequency Selection
        3. 8.2.2.3 Inductor Selection
        4. 8.2.2.4 VCC and Bootstrap Capacitor
        5. 8.2.2.5 Output Capacitor Selection
        6. 8.2.2.6 Current Limit Off-Timer Setting
        7. 8.2.2.7 Rectifier Diode Selection
        8. 8.2.2.8 Input Capacitor Selection
        9. 8.2.2.9 Ripple Configuration
      3. 8.2.3 Application Curves
    3. 8.3 Do's and Don'ts
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Support 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

8.2.2.4 VCC and Bootstrap Capacitor

C3: The capacitor on the VCC output provides not only noise filtering and stability, but also prevents false triggering of the VCC UVLO at the buck switch on and off transitions. For this reason, C3 must be no smaller than 0.1 µF.

C4: The recommended value is 0.022 µF for C4 because this value is appropriate in the majority of applications. A high-quality ceramic capacitor, with low ESR is recommended because C4 supplies the surge current to charge the buck switch gate at turn-on. A low ESR also ensures a quick recharge during each off-time. At minimum VIN when the on-time is at maximum, C4 can possibly not fully recharge at start-up during each 300-ns off-time. This failure to recharge results from the circuit being unable to complete the start-up and achieve output regulation. This condition can occur when the frequency is intended to be low (for example, RON = 500 kΩ). In this case, increase C4 to maintain sufficient voltage across the buck switch driver during each on-time.