SNVS508D October   2007  – September 2016 LM3405A

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 Boost Function
      2. 7.3.2 Setting the LED Current
      3. 7.3.3 Output Voltage
      4. 7.3.4 Enable Mode / Shutdown Mode
      5. 7.3.5 LED PWM Dimming
      6. 7.3.6 Undervoltage Lockout
      7. 7.3.7 Current Limit
      8. 7.3.8 Overcurrent Protection
    4. 7.4 Device Functional Modes
      1. 7.4.1 Thermal Shutdown
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Inductor (L1)
      2. 8.1.2 Input Capacitor (C1)
      3. 8.1.3 Output Capacitor (C2)
      4. 8.1.4 Feed-Forward Capacitor (C4)
      5. 8.1.5 Catch Diode (D1)
      6. 8.1.6 Boost Diode (D2)
      7. 8.1.7 Boost Capacitor (C3)
      8. 8.1.8 Power Loss Estimation
    2. 8.2 Typical Applications
      1. 8.2.1 VBOOST Derived from VIN (VIN = 5 V, IF = 1 A)
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Calculate Duty Cycle (D)
          2. 8.2.1.2.2 Choose Capacitor Values (C1, C2, C3, and C4)
          3. 8.2.1.2.3 Set the Nominal LED Current (R1)
          4. 8.2.1.2.4 Choose Diodes (D1 and D2)
          5. 8.2.1.2.5 Calculate the Inductor Value (L1)
        3. 8.2.1.3 Application Curve
    3. 8.3 System Examples
      1. 8.3.1 VBOOST Derived from VOUT (VIN = 12 V, IF = 1 A)
      2. 8.3.2 VBOOST Derived from VIN through a Series Zener Diode (D3) (VIN = 15 V, IF = 1 A)
      3. 8.3.3 VBOOST Derived from VIN through a Shunt Zener Diode (D3) (VIN = 18 V, IF = 1 A)
      4. 8.3.4 LED MR16 Lamp Application (VIN = 12-V AC, IF = 0.75 A)
      5. 8.3.5 VBOOST Derived from VOUT through a Series Zener Diode (D3) ( VIN = 18 V, IF = 1 A )
  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 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Community Resource
    4. 11.4 Trademarks
      1. 11.3 Community Resource
      2. 11.4 Trademarks
      3. 11.5 Electrostatic Discharge Caution
      4. 11.6 Glossary
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information
  13. 12Mechanical, Packaging, and Orderable Information

Package Options

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

1 Features

  • VIN Operating Range of 3 V to 22 V
  • Drives up to 5 High-Brightness LEDs in Series at 1 A
  • Thin SOT-6 and MSOP-PowerPAD™-8 Packages
  • 1.6-MHz Switching Frequency
  • EN/DIM Input for Enabling and PWM Dimming of LEDs
  • 300-mΩ NMOS Switch
  • 40-nA Shutdown Current at VIN = 5 V
  • Internally Compensated Current-mode Control
  • Cycle-by-Cycle Current Limit
  • Input Voltage UVLO
  • Overcurrent Protection
  • Thermal Shutdown

2 Applications

  • LED Drivers
  • Constant Current Sources
  • Industrial Lighting
  • LED Flashlights
  • LED Lightbulbs

3 Description

The LM3405A is a 1-A constant current buck LED driver designed to provide a simple, high efficiency solution for driving high power LEDs. With a 0.205-V reference voltage feedback control to minimize power dissipation, an external resistor sets the current as needed for driving various types of LEDs. Switching frequency is internally set to 1.6 MHz, allowing small surface mount inductors and capacitors to be used. The LM3405A uses current-mode control and internal compensation offering ease of use and predictable, high performance regulation over a wide range of operating conditions. With a maximum input voltage of 22 V, the device can drive up to 5 High-Brightness LEDs in series at 1-A forward current, with the single LED forward voltage of approximately 3.7 V. Additional features include user accessible EN/DIM pin for enabling and PWM dimming of LEDs, thermal shutdown, cycle-by-cycle current limit and overcurrent protection.

Device Information(1)

PART NUMBER PACKAGE BODY SIZE (NOM)
LM3405A SOT (6) 2.90 mm × 1.60 mm
MSOP-PowerPAD (8) 3.00 mm × 3.00 mm
  1. For all available packages, see the orderable addendum at the end of the data sheet.


Typical Application Circuit

LM3405A 30015201.gif

Efficiency vs LED Current (VIN = 12 V)

LM3405A 30015273.png