SNVS574G July   2008  – July 2019 LM3421 , LM3423

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Typical Boost Application
  4. 4 Revision History
  5. 5 Device Comparison
  6. 6 Pin Configuration and Functions
    1.     Pin 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  Current Regulators
      2. 8.3.2  Predictive Off-Time (PRO) Control
      3. 8.3.3  Average LED Current
      4. 8.3.4  Analog Dimming
      5. 8.3.5  Current Sense and Current Limit
      6. 8.3.6  Overcurrent Protection
      7. 8.3.7  Zero Current Shutdown
      8. 8.3.8  Control Loop Compensation
      9. 8.3.9  Start-Up Regulator
      10. 8.3.10 Overvoltage Lockout (OVLO)
      11. 8.3.11 Input Undervoltage Lockout (UVLO)
        1. 8.3.11.1 UVLO Only
        2. 8.3.11.2 PWM Dimming and UVLO
      12. 8.3.12 PWM Dimming
      13. 8.3.13 LM3423 Only: DPOL, FLT, TIMR, and LRDY
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Inductor
      2. 9.1.2 LED Dynamic Resistance
      3. 9.1.3 Output Capacitor
      4. 9.1.4 Input Capacitors
      5. 9.1.5 Main MOSFET / Dimming MOSFET
      6. 9.1.6 Re-Circulating Diode
      7. 9.1.7 Boost Inrush Current
      8. 9.1.8 Switching Frequency
    2. 9.2 Typical Applications
      1. 9.2.1 Basic Topology Schematics
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
          1. 9.2.1.2.1  Operating Point
          2. 9.2.1.2.2  Switching Frequency
          3. 9.2.1.2.3  Average LED Current
          4. 9.2.1.2.4  Inductor Ripple Current
          5. 9.2.1.2.5  LED Ripple Current
          6. 9.2.1.2.6  Peak Current Limit
          7. 9.2.1.2.7  Loop Compensation
          8. 9.2.1.2.8  Input Capacitance
          9. 9.2.1.2.9  N-channel FET
            1. 9.2.1.2.9.1 Boost and Buck-Boost
          10. 9.2.1.2.10 Diode
          11. 9.2.1.2.11 Output OVLO
          12. 9.2.1.2.12 Input UVLO
          13. 9.2.1.2.13 PWM Dimming Method
          14. 9.2.1.2.14 Analog Dimming Method
      2. 9.2.2 LM3421 Buck-Boost Application
        1. 9.2.2.1 Design Requirements
        2. 9.2.2.2 Detailed Design Procedure
          1. 9.2.2.2.1  Operating Point
          2. 9.2.2.2.2  Switching Frequency
          3. 9.2.2.2.3  Average LED Current
          4. 9.2.2.2.4  Inductor Ripple Current
          5. 9.2.2.2.5  Output Capacitance
          6. 9.2.2.2.6  Peak Current Limit
          7. 9.2.2.2.7  Loop Compensation
          8. 9.2.2.2.8  Input Capacitance
          9. 9.2.2.2.9  N-channel FET
          10. 9.2.2.2.10 Diode
          11. 9.2.2.2.11 Input UVLO
          12. 9.2.2.2.12 Output OVLO
        3. 9.2.2.3 Application Curve
      3. 9.2.3 LM3421 BOOST Application
        1. 9.2.3.1 Design Requirements
        2. 9.2.3.2 Detailed Design Procedure
      4. 9.2.4 LM3421 Buck-Boost Application
        1. 9.2.4.1 Design Requirements
        2. 9.2.4.2 Detailed Design Procedure
      5. 9.2.5 LM3423 Boost Application
        1. 9.2.5.1 Design Requirements
        2. 9.2.5.2 Detailed Design Procedure
      6. 9.2.6 LM3421 Buck-Boost Application
        1. 9.2.6.1 Design Requirements
        2. 9.2.6.2 Detailed Design Procedure
      7. 9.2.7 LM3423 Buck Application
        1. 9.2.7.1 Design Requirements
        2. 9.2.7.2 Detailed Design Procedure
      8. 9.2.8 LM3423 Buck-Boost Application
        1. 9.2.8.1 Design Requirements
        2. 9.2.8.2 Detailed Design Procedure
      9. 9.2.9 LM3421 SEPIC Application
        1. 9.2.9.1 Design Procedure
        2. 9.2.9.2 Detailed Design Procedure
  10. 10Power Supply Recommendations
    1. 10.1 General Recommendations
    2. 10.2 Input Supply Current Limit
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Third-Party Products Disclaimer
    2. 12.2 Related Links
    3. 12.3 Community Resources
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

9.2.4.2 Detailed Design Procedure

Table 4. Bill of Materials

QTY PART ID PART VALUE MANUFACTURER PART NUMBER
1 LM3421 Buck-boost controller TI LM3421MH
1 CB 100-pF COG/NPO 5% 50 V MURATA GRM2165C1H101JA01D
1 CBYP 2.2-µF X7R 10% 16 V MURATA GRM21BR71C225KA12L
3 CCMP, CREF, CSS 1-µF X7R 10% 25 V MURATA GRM21BR71E105KA01L
1 CF 0.1-µF X7R 10% 25 V MURATA GRM21BR71E104KA01L
0 CFS DNP
4 CIN 6.8-µF X7R 10% 50 V TDK C5750X7R1H685K
4 CO 10-µF X7R 10% 50 V TDK C4532X7R1H106K
1 COV 47-pF COG/NPO 5% 50 V AVX 08055A470JAT2A
1 CT 1000-pF COG/NPO 5% 50 V MURATA GRM2165C1H102JA01D
1 D1 Schottky 100 V 12 A VISHAY 12CWQ10FNPBF
1 D2 Zener 10 V 500 mA ON-SEMI BZX84C10LT1G
1 L1 22 µH 20% 7.2 A COILCRAFT MSS1278-223MLB
2 Q1, Q2 NMOS 60 V 8 A VISHAY SI4436DY
1 Q3 NMOS 60 V 260 mA ON-SEMI 2N7002ET1G
1 Q4 PNP 40 V 200 mA FAIRCHILD MMBT5087
1 Q5 PNP 150 V 600 mA FAIRCHILD MMBT5401
1 Q6 NPN 300 V 600 mA FAIRCHILD MMBTA42
1 Q7 NPN 40 V 200 mA FAIRCHILD MMBT6428
1 RCSH 12.4 kΩ 1% VISHAY CRCW080512K4FKEA
1 RF 10 Ω 1% VISHAY CRCW080510R0FKEA
1 RFS 0 Ω 1% VISHAY CRCW08050000Z0EA
1 RUV2 10 kΩ 1% VISHAY CRCW080510K0FKEA
2 RHSP, RHSN 1 kΩ 1% VISHAY CRCW08051K00FKEA
1 RLIM 0.04 Ω 1% 1 W VISHAY WSL2512R0400FEA
1 ROV1 18.2 kΩ 1% VISHAY CRCW080518K2FKEA
1 ROV2 499 kΩ 1% VISHAY CRCW0805499KFKEA
1 RPOT 1-MΩ potentiometer BOURNS 3352P-1-105
1 RPU 4.99 kΩ 1% VISHAY CRCW08054K99FKEA
1 RSER 499 Ω 1% VISHAY CRCW0805499RFKEA
1 RSNS 0.05 Ω 1% 1 W VISHAY WSL2512R0500FEA
1 RT 41.2 kΩ 1% VISHAY CRCW080541K2FKEA
1 RUV1 1.43 kΩ 1% VISHAY CRCW08051K43FKEA
1 RUVH 17.4 kΩ 1% VISHAY CRCW080517K4FKEA