SNVS496F January   2007  – May 2021 LM5002

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 High Voltage VCC Regulator
      2. 7.3.2 Oscillator
      3. 7.3.3 External Synchronization
      4. 7.3.4 Enable and Standby
      5. 7.3.5 Error Amplifier and PWM Comparator
      6. 7.3.6 Current Amplifier and Slope Compensation
      7. 7.3.7 Power MOSFET
    4. 7.4 Device Functional Modes
      1. 7.4.1 Thermal Protection
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 VIN
      2. 8.1.2 SW PIN
      3. 8.1.3 EN or UVLO Voltage Divider Selection
      4. 8.1.4 Soft Start
    2. 8.2 Typical Applications
      1. 8.2.1 Non-Isolated Flyback Regulator
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Switching Frequency
          2. 8.2.1.2.2 Flyback Transformer
          3. 8.2.1.2.3 Peak MOSFET Current
          4. 8.2.1.2.4 Output Capacitance
          5. 8.2.1.2.5 Output Diode Rating
          6. 8.2.1.2.6 Power Stage Analysis
          7. 8.2.1.2.7 Loop Compensation
      2. 8.2.2 Isolated Flyback Regulator
        1. 8.2.2.1 Design Requirements
      3. 8.2.3 Boost Regulator
        1. 8.2.3.1 Design Requirements
      4. 8.2.4 24-V SEPIC Regulator
        1. 8.2.4.1 Design Requirements
      5. 8.2.5 12-V Automotive SEPIC Regulator
        1. 8.2.5.1 Design Requirements
  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 Receiving Notification of Documentation Updates
    2. 11.2 Support Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

7.3.1 High Voltage VCC Regulator

The LM5002 VCC low dropout (LDO) regulator allows the LM5002 to operate at the lowest possible input voltage. The VCC pin voltage is very nearly equal to the input voltage from 2.8 V up to approximately 6.9 V. As the input voltage continues to increase, the VCC voltage is regulated at the 6.9 V set-point. The total input operating range of the VCC LDO regulator is 3.1 V to 75 V.

The output of the VCC regulator is current limited to 20 mA. During power-up, the VCC regulator supplies current into the required decoupling capacitor (0.47 µF or greater ceramic capacitor) at the VCC pin. When the VCC voltage exceeds the VCC UVLO threshold of 2.8 V and the EN pin is greater than 1.26 V the PWM controller is enabled and switching begins. The controller remains enabled until VCC falls below 2.7 V or the EN pin falls below 1.16 V.

An auxiliary supply voltage can be applied to the VCC pin to reduce the IC power dissipation. If the auxiliary voltage is greater than 6.9 V, the internal regulator essentially shuts-off, and internal power dissipation is decreased by the VIN voltage times the operating current. The overall converter efficiency also improves if the VIN voltage is much higher than the auxiliary voltage. Do not exceed 14 V with an externally applied VCC voltage. The VCC regulator series pass MOSFET includes a body diode (see Section 7.2) between VCC and VIN that must not be forward biased in normal operation. Therefore, the auxiliary VCC voltage must never exceed the VIN voltage.

In high voltage applications take extra care to ensure the VIN pin does not exceed the absolute maximum voltage rating of 76 V. Voltage ringing on the VIN line during line transients that exceeds the Absolute Maximum Ratings can damage the IC. Both careful PCB layout and the use of quality bypass capacitors placed close to the VIN and GND pins are essential.