SNVS961F April   2013  – October 2026 LM5023

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 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 Detailed Pin Description
        1. 6.3.1.1 QR Pin
        2. 6.3.1.2 VSD Pin
        3. 6.3.1.3 SS Pin
        4. 6.3.1.4 COMP Pin
        5. 6.3.1.5 CS Pin
        6. 6.3.1.6 GND Pin
        7. 6.3.1.7 OUT Pin
        8. 6.3.1.8 VCC Pin
      2. 6.3.2 Start-Up
      3. 6.3.3 Quasi-Resonant Operation
      4. 6.3.4 Quasi-Resonant Operating Frequency
      5. 6.3.5 PWM Comparator
      6. 6.3.6 Soft-Start
      7. 6.3.7 Gate Driver
        1. 6.3.7.1 Skip-Cycle Operation
      8. 6.3.8 Current Limit and Current Sense
    4. 6.4 Device Functional Modes
  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 Line Current-Limit Feedforward
          1. 7.2.2.2.1 Overvoltage Protection
        3. 7.2.2.3 Valley Switching
        4. 7.2.2.4 Hiccup Mode
      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 Development Support
        1. 8.1.1.1 Custom Design With WEBENCH® Tools
    2. 8.2 Documentation Support
      1. 8.2.1 Related Documentation
    3. 8.3 Receiving Notification of Documentation Updates
    4. 8.4 Community Resources
    5. 8.5 Trademarks
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

Package Options

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

7.2.2.4 Hiccup Mode

Hiccup Mode is a method to prevent the power supply from over-heating during and extended overload condition. In an overload fault, the current limit comparator turns off the driver output on pulse-by-pulse basis. This starts the over load detection timer, after the over load detection timer (OLDT) times out, the current limit comparator is rechecked, if the power supply is still in an overload condition, the OUT drive is latched-off and VCC is allowed to drop to VCCOFF (7.5V).

When VCC reaches VCCOFF, the VSD open-drain output is disabled allowing the depletion mode start-up FET to turn-on, charging up the VCC capacitor to VCCON (12.5V). When VCC reaches VCCON, the VSD output goes low turning-off the depletion mode FET. The VCC capacitor is discharged from VCCON to VCCOFF at a rate proportional to the VCC capacitor and the ICCST current (340µA typical). The charging and discharging of the VCC capacitor is repeated four times (refer to Figure 7-4) use Equation 57 to figure the total Hiccup time.

Equation 57. tHICCUP=tCHARGE×4+tDISCHARGE×4

After allowing VCC to charge and discharge four times, the LM5023 goes through an auto restart sequence, enabling the LM5023 soft start and driver output. It is important to set the over load detection timer long enough so that under low input-line and full-load conditions that the power supply has enough time to start-up.

The over load detection timer can be set with the resister in series with the VSD pinVSD), refer to Figure 6-1.

Equation 58. IVSD=VCCRVSD=10V1MΩ=10μA
Equation 59. OVER_LOAD_DETECTION_TIMER=2×60nAIVSD=2×60nA10μA=12ms

Normally it is recommended that RVSD > 1MΩ, if a lower value is used then the standby power is higher.

Assuming the depletion mode FET charges the VCC capacitor with 2mA, VCC capacitor is 10µF.

Equation 60. tCHARGE=(VCCON−VCCOFF)ICHARGE×CVCC=12.5V−7.5V2mA×10μF=25ms
Equation 61. tDISCHARGE=(VCCON−VCCOFF)ICCST×CVCC=12.5V−7.5V340μA×10μF =145ms
Equation 62. tHICCUP=25ms×4+145ms×4=680ms
LM5023 Hiccup Mode TimingFigure 7-4 Hiccup Mode Timing