SNVSB97A December   2018  – September 2021 LM34936-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
    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  Fixed Frequency Valley/Peak Current Mode Control with Slope Compensation
      2. 7.3.2  VCC Regulator and Optional BIAS Input
      3. 7.3.3  Enable/UVLO
      4. 7.3.4  Soft Start
      5. 7.3.5  Overcurrent Protection
      6. 7.3.6  Average Input/Output Current Limiting
      7. 7.3.7  Operation Above 28-V Input
      8. 7.3.8  CCM Operation
      9. 7.3.9  Frequency and Synchronization (RT/SYNC)
      10. 7.3.10 Frequency Dithering
      11. 7.3.11 Output Overvoltage Protection (OVP)
      12. 7.3.12 Power Good (PGOOD)
      13. 7.3.13 Gm Error Amplifier
      14. 7.3.14 Integrated Gate Drivers
      15. 7.3.15 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Shutdown, Standby, and Operating Modes
      2. 7.4.2 MODE Pin Configuration
  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  Custom Design with WEBENCH Tools
        2. 8.2.2.2  Frequency
        3. 8.2.2.3  VOUT
        4. 8.2.2.4  Inductor Selection
        5. 8.2.2.5  Output Capacitor
        6. 8.2.2.6  Input Capacitor
        7. 8.2.2.7  Sense Resistor (RSENSE)
        8. 8.2.2.8  Slope Compensation
        9. 8.2.2.9  UVLO
        10. 8.2.2.10 Soft-Start Capacitor
        11. 8.2.2.11 Dither Capacitor
        12. 8.2.2.12 MOSFETs QH1 and QL1
        13. 8.2.2.13 MOSFETs QH2 and QL2
        14. 8.2.2.14 Frequency Compensation
      3. 8.2.3 Application Curves
  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 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 Receiving Notification of Documentation Updates
    4. 11.4 Support Resources
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

7.3.5 Overcurrent Protection

The LM34936-Q1 provides cycle-by-cycle current limit to protect against overcurrent and short circuit conditions. In buck operation, the sensed valley voltage across the CSG and CS pins is limited to VCS(BUCK). The high-side buck switch skips a cycle if the sensed voltage does not fall below this threshold during the buck switch off time. In boost operation, the maximum peak voltage across CS and CSG is limited to VCS(BOOST). If the peak current in the low-side boost switch causes the voltage across CS and CSG to exceed this threshold voltage, the boost switch is turned off for the remainder of the clock cycle.

Applying the appropriate voltage to the MODE pin of the LM34936-Q1 enables Hiccup mode fault protection (see Section 7.4.2). In Hiccup mode, the controller shuts down after detecting cycle-by-cycle current limiting for 128 consecutive cycles and the soft-start capacitor is discharged. The soft-start capacitor is automatically released after 4000 oscillator clock cycles and the controller restarts. If Hiccup mode protection is not enabled through the MODE pin, the LM34936-Q1 operates in cycle-by-cycle current limiting as long as the overload condition persists.