SNVS429C October   2006  – December 2016 LM3405

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 or 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)
        1. 8.3.1.1 Bill of Materials
      2. 8.3.2 VBOOST Derived From VIN Through a Series Zener Diode, D3 (VIN = 15 V, IF = 1 A)
        1. 8.3.2.1 Bill of Materials
      3. 8.3.3 VBOOST Derived From VIN Through a Shunt Zener Diode, D3 (VIN = 15 V, IF = 1 A)
        1. 8.3.3.1 Bill of Materials
      4. 8.3.4 VBOOST Derived from VOUT Through a Series Zener Diode, D3 (VIN = 15 V, IF = 1 A)
        1. 8.3.4.1 Bill of Materials
  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
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

5 Pin Configuration and Functions

DDC Package
6-Pin SOT
Top View
LM3405 30015205.gif
DDC Package
6-Pin SOT
Pin 1 Identification
LM3405 20178960.gif

Pin Functions

PIN I/O DESCRIPTION
NO. NAME
1 BOOST O Boost voltage that drives the NMOS output switch. A bootstrap capacitor is connected between the BOOST and SW pins.
2 GND — Signal and power ground pin. Place the bottom resistor of the feedback network as close as possible to this pin.
3 FB I Feedback pin. Connect FB to the LED string cathode and an external resistor to ground to set the LED current.
4 EN/DIM I Enable control input. Logic high enables operation. Toggling this pin with a periodic logic square wave of varying duty cycle at different frequencies controls the brightness of LEDs. Do not allow this pin to float or be greater than VIN + 0.3 V.
5 VIN I Input supply voltage. Connect a bypass capacitor locally from this pin to GND.
6 SW O Switch pin. Connect this pin to the inductor, catch diode, and bootstrap capacitor.