SNVSBM6A April   2020  – January 2021 LM5181

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Description (continued)
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1  Integrated Power MOSFET
      2. 8.3.2  PSR Flyback Modes of Operation
      3. 8.3.3  Setting the Output Voltage
        1. 8.3.3.1 Diode Thermal Compensation
      4. 8.3.4  Control Loop Error Amplifier
      5. 8.3.5  Precision Enable
      6. 8.3.6  Configurable Soft Start
      7. 8.3.7  External Bias Supply
      8. 8.3.8  Minimum On-Time and Off-Time
      9. 8.3.9  Overcurrent Protection
      10. 8.3.10 Thermal Shutdown
    4. 8.4 Device Functional Modes
      1. 8.4.1 Shutdown Mode
      2. 8.4.2 Standby Mode
      3. 8.4.3 Active Mode
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Applications
      1. 9.2.1 Design 1: Wide VIN, Low IQ PSR Flyback Converter Rated at 5 V, 0.5 A
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
          1. 9.2.1.2.1  Custom Design With WEBENCH® Tools
          2. 9.2.1.2.2  Custom Design With Excel Quickstart Tool
          3. 9.2.1.2.3  Flyback Transformer – T1
          4. 9.2.1.2.4  Flyback Diode – DFLY
          5. 9.2.1.2.5  Zener Clamp Circuit – DF, DCLAMP
          6. 9.2.1.2.6  Output Capacitor – COUT
          7. 9.2.1.2.7  Input Capacitor – CIN
          8. 9.2.1.2.8  Feedback Resistor – RFB
          9. 9.2.1.2.9  Thermal Compensation Resistor – RTC
          10. 9.2.1.2.10 UVLO Resistors – RUV1, RUV2
          11. 9.2.1.2.11 Soft-Start Capacitor – CSS
      2. 9.2.2 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Examples
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Third-Party Products Disclaimer
      2. 12.1.2 Development Support
        1. 12.1.2.1 Custom Design With WEBENCH® Tools
    2. 12.2 Documentation Support
      1. 12.2.1 Related Documentation
    3. 12.3 Receiving Notification of Documentation Updates
    4. 12.4 Support Resources
    5. 12.5 Trademarks
    6. 12.6 Electrostatic Discharge Caution
    7. 12.7 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

9.2.1.1 Design Requirements

The required input, output, and performance parameters for this application example are shown in Table 9-1.

Table 9-1 Design Parameters
DESIGN PARAMETERVALUE
Input voltage range10 V to 65 V
Input UVLO thresholds9.5 V on, 6.5 V off
Output voltage5 V
Rated load current, VIN = 24 V0.5 A
Output voltage regulation±1.5%
Output voltage ripple< 100 mV

The target full-load efficiency is 87.5% based on a nominal input voltage of 24 V and an isolated output voltage of 5 V. The LM5181 is chosen to deliver a fixed 5-V output voltage set by resistor RFB connected between the SW and FB pins. The input voltage turnon and turnoff thresholds are established by RUV1 and RUV2. The required components are listed in Table 9-2. Transformers for other designs are listed in Table 9-3.

Table 9-2 List of Components for Design 1
REF DESQTYSPECIFICATIONVENDORPART NUMBER
CIN12.2 µF, 100 V, X7R, 1206, ceramicAVX12061C225KAT4A
2.2 µF, 100 V, X7R, 1210, ceramicTDKC3225X7R2A225K230AB
MurataGCJ32DR72A225KA01L
Taiyo YudenHMK325B7225KN-T
COUT147 µF, 10 V, X7S, 1210, ceramicTDKC3225X7S1A476M250AC
47 µF, 10 V, X7R, 1210, ceramicMurataGRM32ER71A476KE15L
Taiyo YudenLMK325B7476MM-TR
CSS147 nF, 16 V, X7R, 0402StdStd
DCLAMP1Zener, 24 V, 1 W, PowerDI-123DFLZ24-7Diodes Inc.
DF1Switching diode, 75 V, 0.25 A, SOD-323CMDD4448Central Semi
DFLY1Schottky diode, 40 V, 2 A, SOD-123FSV340FPOnsemi
DOUT1Zener, 5.6 V, 5%, SOD-523BZX585-C5V6Nexperia
RFB1158 kΩ, 1%, 0402StdStd
RSET112.1 kΩ, 1%, 0402StdStd
RTC1130 kΩ, 1%, 0402StdStd
RUV11536 kΩ, 1%, 0603StdStd
RUV21100 kΩ, 1%, 0402StdStd
T1144 µH, 1.4 A, 3 : 1, 8.2 × 8.6 × 9.6 mmWürth Electronik750318633
U11LM5181 PSR flyback converter, VSON-8Texas InstrumentsLM5181NGUR
Table 9-3 Magnetic Components for Various Output Voltages
OUTPUT VOLTAGE (RANGE)TURNS RATIOLMAG, ISATDIMENSIONSVENDORPART NUMBER
3.3 V (up to 4 V)4 : 140 µH, 1 A8.6 × 8.26 × 9.65 mmWürth Electronik750319117
5 V (4 V to 5.5 V)3 : 144 µH, 1 A750318633
12 V (5.5 V to 16 V)1 : 1750318737
24 V (16 V to 32 V)1 : 2750318738
48 V (32 V to 50 V)1 : 3750319118
15 V and –7.5 V dual1 : 1.5 : 0.830 µH, 1 A750319119