SNVS967A August   2014  – November 2014 LM3643

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Simplified Schematic
  5. 5 Revision History
  6. 6 Device Comparison Table
  7. 7 Pin Configuration and Functions
  8. 8 Specifications
    1. 8.1 Absolute Maximum Ratings
    2. 8.2 Handling Ratings
    3. 8.3 Recommended Operating Conditions
    4. 8.4 Thermal Information
    5. 8.5 Electrical Characteristics
    6. 8.6 Timing Requirements
    7. 8.7 Switching Characteristics
    8. 8.8 Typical Characteristics
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 Flash Mode
      2. 9.3.2 Torch Mode
      3. 9.3.3 IR Mode
    4. 9.4 Device Functioning Modes
      1. 9.4.1 Start-Up (Enabling The Device)
      2. 9.4.2 Pass Mode
      3. 9.4.3 Power Amplifier Synchronization (TX)
      4. 9.4.4 Input Voltage Flash Monitor (IVFM)
      5. 9.4.5 Fault/Protections
        1. 9.4.5.1 Fault Operation
        2. 9.4.5.2 Flash Time-Out
        3. 9.4.5.3 Overvoltage Protection (OVP)
        4. 9.4.5.4 Current Limit
        5. 9.4.5.5 NTC Thermistor Input (Torch/Temp)
        6. 9.4.5.6 Undervoltage Lockout (UVLO)
        7. 9.4.5.7 Thermal Shutdown (TSD)
        8. 9.4.5.8 LED and/or VOUT Short Fault
    5. 9.5 Programming
      1. 9.5.1 Control Truth Table
      2. 9.5.2 I2C-Compatible Interface
        1. 9.5.2.1 Data Validity
        2. 9.5.2.2 Start and Stop Conditions
        3. 9.5.2.3 Transferring Data
        4. 9.5.2.4 I2C-Compatible Chip Address
    6. 9.6 Register Descriptions
      1. 9.6.1  Enable Register (0x01)
      2. 9.6.2  IVFM Register (0x02)
      3. 9.6.3  LED1 Flash Brightness Register (0x03)
      4. 9.6.4  LED2 Flash Brightness Register (0x04)
      5. 9.6.5  LED1 Torch Brightness Register (0x05)
      6. 9.6.6  LED2 Torch Brightness Register (0x06)
      7. 9.6.7  Boost Configuration Register (0x07)
      8. 9.6.8  Timing Configuration Register (0x08)
      9. 9.6.9  TEMP Register (0x09)
      10. 9.6.10 Flags1 Register (0x0A)
      11. 9.6.11 Flags2 Register (0x0B)
      12. 9.6.12 Device ID Register (0x0C)
      13. 9.6.13 Last Flash Register (0x0D)
  10. 10Applications and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
        1. 10.2.2.1 Output Capacitor Selection
        2. 10.2.2.2 Input Capacitor Selection
        3. 10.2.2.3 Inductor Selection
      3. 10.2.3 Application Curves
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
  13. 13Device and Documentation Support
    1. 13.1 Device Support
      1. 13.1.1 Third-Party Products Disclaimer
    2. 13.2 Related Documentation
      1. 13.2.1 Related Links
    3. 13.3 Trademarks
    4. 13.4 Electrostatic Discharge Caution
    5. 13.5 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

1 Features

  • 1.5 A Total Allowed LED Current During Operation
    (ILED1 + ILED2 = 1.5 A)
  • Dual Independent LED Current Source Programmability
  • Accurate and Programmable LED Current Range from 1.4 mA to 1.5 A
  • Optimized Flash LED Current During Low Battery Conditions (IVFM)
  • > 85% Efficiency in Torch Mode (@ 100 mA) and Flash Mode (@1 A to 1.5 A)
  • Grounded Cathode LED Operation for Improved Thermal Management
  • Small Solution Size: < 16 mm2
  • Hardware Strobe Enable (STROBE)
  • Synchronization Input for RF Power Amplifier Pulse Events (TX)
  • Hardware Torch Enable (TORCH/TEMP)
  • Remote NTC Monitoring (TORCH/TEMP)
  • 400-kHz I2C-Compatible Interface
    • LM3643 (I2C Address = 0x63)
    • LM3643A (I2C Address = 0x67)

2 Applications

    Camera Phone White LED Flash

3 Description

The LM3643 is a dual LED flash driver that provides a high level of adjustability within a small solution size. The LM3643 utilizes a 2-MHz or 4-MHz fixed-frequency synchronous boost converter to provide power to the dual 1.5-A constant current LED sources. The total LED current the LM3643 boost can deliver is 1.5 A (ILED1 + ILED2 ). The dual 128 level current sources provide the flexibility to adjust the current ratios between LED1 and LED2 with each driver capable of delivering a maximum of 1.5 A (ex: ILED1 = 1.5 A and ILED2 = 0FF, ILED1 = 0FF and ILED2 = 1.5 A, or a current configuration with a current less than 1.5 A , ILED1 = 950 mA and ILED2 = 250 mA). An adaptive regulation method ensures the current sources remain in regulation and maximizes efficiency.

Features of the LM3643 are controlled via an I2C-compatible interface. These features include: hardware flash and hardware torch pins (STROBE and TORCH/TEMP), a TX interrupt, and an NTC thermistor monitor. The device offers independently programmable currents in each output leg to drive the LEDs in a Flash or Movie Mode (Torch) condition.

The 2-MHz or 4-MHz switching frequency options, overvoltage protection (OVP), and adjustable current limit allow for the use of tiny, low-profile inductors and (10-µF) ceramic capacitors. The device operates over a –40°C to 85°C ambient temperature range.

Device Information(1)

PART NUMBER PACKAGE BODY SIZE (MAX)
LM3643 DSBGA (12) 1.69 mm x 1.31 mm
  1. For all available packages, see the orderable addendum at the end of the datasheet.

4 Simplified Schematic

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