SNVS499I February   2007  – November 2023 LM5116

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
    6. 5.6 Switching Characteristics
    7. 5.7 Typical Performance Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 High Voltage Start-Up Regulator
      2. 6.3.2 Enable
      3. 6.3.3 UVLO
      4. 6.3.4 Oscillator and Sync Capability
      5. 6.3.5 Error Amplifier and PWM Comparator
      6. 6.3.6 Ramp Generator
      7. 6.3.7 Current Limit
      8. 6.3.8 HO Output
      9. 6.3.9 Thermal Protection
    4. 6.4 Device Functional Modes
      1. 6.4.1 Soft-Start and Diode Emulation
  8. 7 Application and Implementation
    1. 7.1 Application Information
    2. 7.2 Typical Application
      1. 7.2.1 Design Requirements
      2. 7.2.2 Detailed Design Procedure
        1. 7.2.2.1  Custom Design with WEBENCH® Tools
        2. 7.2.2.2  Timing Resistor
        3. 7.2.2.3  Output Inductor
        4. 7.2.2.4  Current Sense Resistor
        5. 7.2.2.5  Ramp Capacitor
        6. 7.2.2.6  Output Capacitors
        7. 7.2.2.7  Input Capacitors
        8. 7.2.2.8  VCC Capacitor
        9. 7.2.2.9  Bootstrap Capacitor
        10. 7.2.2.10 Soft Start Capacitor
        11. 7.2.2.11 Output Voltage Divider
        12. 7.2.2.12 UVLO Divider
        13. 7.2.2.13 MOSFETs
        14. 7.2.2.14 MOSFET Snubber
        15. 7.2.2.15 Error Amplifier Compensation
        16. 7.2.2.16 Comprehensive Equations
          1. 7.2.2.16.1 Current Sense Resistor and Ramp Capacitor
          2. 7.2.2.16.2 Modulator Transfer Function
          3. 7.2.2.16.3 Error Amplifier Transfer Function
      3. 7.2.3 Application Curves
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
      2. 7.4.2 Layout Example
  9. 8 Device and Documentation Support
    1. 8.1 Device Support
      1. 8.1.1 Third-Party Products Disclaimer
      2. 8.1.2 Development Support
        1. 8.1.2.1 Custom Design with WEBENCH® Tools
    2. 8.2 Receiving Notification of Documentation Updates
    3. 8.3 Support Resources
    4. 8.4 Trademarks
    5. 8.5 Electrostatic Discharge Caution
    6. 8.6 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

Package Options

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

6.3.3 UVLO

An undervoltage lockout pin is provided to disable the regulator without entering shutdown. If the UVLO pin is pulled below 1.215 V, the regulator enters a standby mode of operation with the soft-start capacitor discharged and outputs disabled, but with the VCC regulator running. If the UVLO input is pulled above 1.215 V, the controller will resume normal operation. A voltage divider from input to ground can be used to set a VIN threshold to disable the supply in brown-out conditions or for low input faults. The UVLO pin has a 5-µA internal pull up current that allows this pin to left open if the input undervoltage lockout function is not needed. For applications which require fast on/off cycling, the UVLO pin with an open collector control signal can be used to ensure proper start-up sequencing.

The UVLO pin is also used to implement a “hiccup” current limit. If a current limit fault exists for more than 256 consecutive clock cycles, the UVLO pin will be internally pulled down to 200 mV and then released, and a new SS cycle initiated. A capacitor to ground connected to the UVLO pin will set the timing for hiccup mode current limit. When this feature is used in conjunction with the voltage divider, a diode across the top resistor can be used to discharge the capacitor in the event of an input undervoltage condition. There is a 5-µs filter at the input to the fault comparator. At higher switching frequency (greater than approximately 250 kHz) the hiccup timer can be disabled if the fault capacitor is not used.