SNVSBL7A March   2020  – August 2020 LM25184

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin 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  Integrated Power MOSFET
      2. 7.3.2  PSR Flyback Modes of Operation
      3. 7.3.3  Setting the Output Voltage
        1. 7.3.3.1 Diode Thermal Compensation
      4. 7.3.4  Control Loop Error Amplifier
      5. 7.3.5  Precision Enable
      6. 7.3.6  Configurable Soft Start
      7. 7.3.7  External Bias Supply
      8. 7.3.8  Minimum On-Time and Off-Time
      9. 7.3.9  Overcurrent Protection
      10. 7.3.10 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Shutdown Mode
      2. 7.4.2 Standby Mode
      3. 7.4.3 Active Mode
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 Design 1: Wide VIN, Low IQ PSR Flyback Converter Rated at 12 V, 1 A
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1  Custom Design With WEBENCH® Tools
          2. 8.2.1.2.2  Custom Design With Excel Quickstart Tool
          3. 8.2.1.2.3  Flyback Transformer – T1
          4. 8.2.1.2.4  Flyback Diode – DFLY
          5. 8.2.1.2.5  Leakgae Inductance Clamp Circuit – DF, DCLAMP
          6. 8.2.1.2.6  Output Capacitor – COUT
          7. 8.2.1.2.7  Input Capacitor – CIN
          8. 8.2.1.2.8  Feedback Resistor – RFB
          9. 8.2.1.2.9  Thermal Compensation Resistor – RTC
          10. 8.2.1.2.10 UVLO Resistors – RUV1, RUV2
          11. 8.2.1.2.11 Soft-Start Capacitor – CSS
      2. 8.2.2 Application Curves
      3. 8.2.3 Design 2: PSR Flyback Converter With Dual Outputs of 15 V and –8 V at 0.5 A
        1. 8.2.3.1 Design Requirements
        2. 8.2.3.2 Detailed Design Procedure
          1. 8.2.3.2.1 Flyback Transformer – T1
          2. 8.2.3.2.2 Flyback Diodes – DFLY1 and DFLY2
          3. 8.2.3.2.3 Input Capacitor – CIN
          4. 8.2.3.2.4 Output Capacitors – COUT1, COUT2
          5. 8.2.3.2.5 Feedback Resistor – RFB
          6. 8.2.3.2.6 Thermal Compensation Resistor – RTC
          7. 8.2.3.2.7 Output Voltage Clamp Zeners – DOUT1 and DOUT2
        3. 8.2.3.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Examples
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
      2. 11.1.2 Development Support
        1. 11.1.2.1 Custom Design With WEBENCH® Tools
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Receiving Notification of Documentation Updates
    4. 11.4 Support Resources
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

8.2.1.1 Design Requirements

The required input, output, and performance parameters for this application example are shown in Table 8-1.

Table 8-1 Design Parameters
DESIGN PARAMETER VALUE
Input voltage range 6 V to 36 V
Input UVLO thresholds 5.5 V on, 4 V off
Output voltage 12 V
Rated load current, VIN ≥ 13.5 V 1 A
Output voltage regulation ±1.5%
Output voltage ripple < 120 mV pk-pk

The target full-load efficiency is 89% based on a nominal input voltage of 24 V and an isolated output voltage of 12 V. The LM25184 is chosen to deliver a fixed 12-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 8-2. Transformers for other single-output designs are listed in Table 8-3.

Table 8-2 List of Components for Design 1
REF DES QTY SPECIFICATION VENDOR PART NUMBER
CIN 1 10 µF, 50 V, X7R, 1210, ceramic TDK CNA6P1X7R1H106K250AE
COUT1 4 22 µF, 25 V, X7R, 1210, ceramic TDK CNA6P1X7R1H106K250AE
Taiyo Yuden TMK325B7226MM-PR
COUT2 0 100 µF, 16 V, ±20%, electrolytic Kemet T598D107M016ATE050
CSS 1 47 nF, 16 V, X7R, 0402 Std Std
DCLAMP 1 Zener, 20 V, 3 W, SMA 3SMAJ5932B Micro Commercial
DF, DFLY 2 Schottky diode, 60 V, 3 A, SOD-123FL FSV360FP OnSemi
DOUT 1 Zener, 13 V, 2%, SOD-523 BZX585-B13 Nexperia
RFB 1 121 kΩ, 1%, 0402 Std Std
RSET 1 12.1 kΩ, 1%, 0402 Std Std
RTC 1 261 kΩ, 1%, 0402 Std Std
RUV1 1 261 kΩ, 1%, 0603 Std Std
RUV2 1 97.6 kΩ, 1%, 0402 Std Std
T1 1 7 μH, 5 A, 1 : 1, 13 mm × 11 mm × 10 mm Coilcraft ZA9672-BE
Sumida 12387-T162
7 μH, 5 A, 1 : 1, 9.8 mm × 9.5 mm ×10.6 mm Würth Electronik 750318701
U1 1 LM25184 PSR flyback converter, VSON-8 Texas Instruments LM25184NGUR
Table 8-3 Magnetic Components for Single-Output Designs
OUTPUT VOLTAGE RANGE TURNS RATIO LMAG, ISAT DIMENSIONS VENDOR PART NUMBER
3.3 V to 5 V 3 : 1 9 µH, 5 A 13 × 11 × 10 mm Coilcraft ZA9671-BE
5 V to 12 V 1 : 1 7 µH, 5 A ZA9672-BE
12 V to 24 V 1 : 2 7 µH, 5 A ZA9673-BE
24 V to 48 V 1 : 3 9 µH, 5 A ZA9674-BE
3.3 V to 6 V 2 : 1 7 µH, 5 A 12 × 10 × 6 mm ZB1067-AE