SNVS594G December   2008  – April 2016 LM3555

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 Control Interface Timing Requirements
    7. 6.7 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  Synchronous Boost Converter
      2. 7.3.2  High-Side Current Source
      3. 7.3.3  I2C/EN Pin
      4. 7.3.4  SDA/EN2 and SCL/EN1 Pins
      5. 7.3.5  STROBE Pin
      6. 7.3.6  TORCH Pin
      7. 7.3.7  Indicator LED Pin (IND)
      8. 7.3.8  Internal Diode Detection
      9. 7.3.9  Fault Protections
        1. 7.3.9.1 Output Overvoltage Protection (OVP)
        2. 7.3.9.2 Output and LED Short-Circuit Protection (SCP)
        3. 7.3.9.3 Overtemperature Protection (OTP)
        4. 7.3.9.4 Flash Timeout (FTP)
        5. 7.3.9.5 Indicator Fault (IF)
        6. 7.3.9.6 Broken Inductor Fault (IP)
      10. 7.3.10 Undervoltage Lockout (UVLO)
      11. 7.3.11 Power-On Reset (POR)
    4. 7.4 Device Functional Modes
      1. 7.4.1 Single LED Operation
      2. 7.4.2 Dual LED Operation
      3. 7.4.3 Torch or Assist (Continuous Current) Operation
      4. 7.4.4 Flash (Pulsed Current) Operation
      5. 7.4.5 Indicator Operation
      6. 7.4.6 Simple Control State Diagram
    5. 7.5 Programming
      1. 7.5.1 I2C-Compatible Interface
        1. 7.5.1.1 Data Validity
        2. 7.5.1.2 Start and Stop Conditions
        3. 7.5.1.3 Transferring Data
        4. 7.5.1.4 I2C-Compatible Chip Address
    6. 7.6 Register Maps
      1. 7.6.1 Internal Registers of LM3555
      2. 7.6.2 Register Definitions
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Inductor Current Limit
        2. 8.2.2.2 Inductor Selection
        3. 8.2.2.3 Capacitor Selection
      3. 8.2.3 Application Curves
  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 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Community Resources
    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

1 Features

  • High-Voltage High-Side Current Source Allows for Grounded Cathode LED Operation
  • Synchronous Boost Converter
  • Peak Converter Efficiency > 90%
  • Accurate and Programmable LED Current Ranging From 60 mA to 500 mA
  • Adaptive LED Current Range Based on LED Configuration
  • Dedicated Indicator Current Source
  • Dedicated Torch and Strobe Pins
  • Dual Mode Control (General Purpose or I2C)
  • Broken Inductor Detection
  • Output Overvoltage Protection
  • Output and LED Short-Circuit Protection
  • 400-kHz I2C-Compatible Interface

2 Applications

    Camera Phone LED Flash

3 Description

The LM3555 is a 2-MHz fixed-frequency, current-mode synchronous boost converter designed to drive either a single flash LED at 500 mA or two series flash LEDs at 400 mA. A high-voltage current source allows the LEDs to be terminated to the GND plane eliminating the need for an additional return trace back to the device.

A dual-mode control interface allows the user to configure the LM3555 with a general-purpose interface using two enable pins for control or an I2C allowing a higher level of control. Both interfaces allow access to the indicator, assist light, and flash modes. A dedicated STROBE pin provides a direct interface to trigger the flash event, while an external TORCH pin provides an additional method for enabling the LEDs in a constant current mode.

The LM3555 can adaptively scale the maximum flash level delivered to the LEDs based upon the flash configuration, whether it be a single LED or two LEDs in series.

Eight protection features are available on the LM3555 ranging from overvoltage protection to broken inductor detection. The LM3555 has four selectable inductor current limits to help the user select an inductor that is appropriate for the design.

Device Information(1)

PART NUMBER PACKAGE BODY SIZE (MAX)
LM3555 DSBGA (12) 2.09 mm × 1.565 mm
  1. For all available packages, see the orderable addendum at the end of the data sheet.

Typical Application

LM3555 30079401.gif