SNVS363E August   2005  – November 2015 LM5026


  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Pin Configuration and Functions
  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. Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  High Voltage Start-Up Regulator
      2. 7.3.2  Line Undervoltage Detector
      3. 7.3.3  PWM Outputs
      4. 7.3.4  Gate Driver Outputs
      5. 7.3.5  PWM Comparator/Slope Compensation
      6. 7.3.6  Maximum Duty Cycle Clamp
      7. 7.3.7  Soft-Start / Soft-Stop
      8. 7.3.8  Current Sense and Current Limit
      9. 7.3.9  Overload Protection Timer
      10. 7.3.10 Oscillator and Sync Capability
      11. 7.3.11 Thermal Protection
    4. 7.4 Device Functional Modes
  8. Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Line Input (VIN)
      2. 8.1.2 For Application > 100 V
      3. 8.1.3 Undervoltage Lockout (UVLO)
      4. 8.1.4 Oscillator (RT, SYNC)
      5. 8.1.5 Voltage Feedback (COMP)
      6. 8.1.6 Current Sense (CS)
      7. 8.1.7 Hiccup Mode Current Limit Restart (RES)
      8. 8.1.8 Soft-Start (SS)
      9. 8.1.9 Voltage-Dependent Maximum Duty Cycle
        1. Programmable Maximum Duty Cycle Clamp (DCL)
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. Determine VIN Configuration
        2. Determine UVLO Configuration
        3. Configure Operating Frequency
        4. Configure Hiccup Mode and Soft Start
        5. Determine Deadtime and Maximum Duty Cycle
      3. 8.2.3 Application Curves
  9. Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Community Resources
    2. 11.2 Trademarks
    3. 11.3 Electrostatic Discharge Caution
    4. 11.4 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

10 Layout

10.1 Layout Guidelines

The LM5026 current-sense and PWM comparators are very fast, and respond to short duration noise pulses. The components at the CS, COMP, SS, DCL, UVLO, TIME, SYNC and the RT pins should be as physically close as possible to the IC, thereby minimizing noise pick-up on the PCB tracks.

Layout considerations are critical for the current-sense filter. If a current-sense transformer is used, both leads of the transformer secondary should be routed to the sense filter components and to the IC pins. The ground side of each transformer should be connected through a dedicated PCB track to the AGND pin, rather than through the ground plane.

If the current-sense circuit employs a sense resistor in the drive transistor source, low inductance resistor should be used. In this case, all the noise-sensitive, low-current ground tracks should be connected in common near the IC, and then a single connection made to the power ground (sense resistor ground point). The gate drive outputs of the LM5026 should have short direct paths to the power MOSFETs in order to minimize inductance in the PCB traces.

The two ground pins (AGND, PGND) must be connected together with a short direct connection to avoid jitter due to relative ground bounce.

If the internal dissipation of the LM5026 produces high junction temperatures during normal operation, the use of multiple vias under the IC to a ground place can help conduct heat away from the IC. Judicious positioning of the PCB within the end product, along with use of any available air flow (forced or natural convection) can help reduce the junction temperatures.

10.2 Layout Example

LM5026 layout_example_SNVS363.gif Figure 38. Layout Example