SNVSCV4 September   2024 LM3645

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
    6. 5.6 Timing Requirements
    7. 5.7 Switching Characteristics
    8. 5.8 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 Power Amplifier Synchronization (TORCH/TX)
      2. 6.3.2 Input Voltage Flash Monitor (IVFM)
      3. 6.3.3 Fault/Protections
        1. 6.3.3.1  Fault Operation
        2. 6.3.3.2  Flash Time-Out
        3. 6.3.3.3  Overvoltage Protection (OVP)
        4. 6.3.3.4  Current Limit
        5. 6.3.3.5  NTC Thermistor Input/Outputs (TEMP1, TEMP2)
        6. 6.3.3.6  Thermal Scale Back
        7. 6.3.3.7  Thermal Shutdown (TSD)
        8. 6.3.3.8  Undervoltage Lockout (UVLO)
        9. 6.3.3.9  LED and/or VOUT Short Fault
        10. 6.3.3.10 Fault Behavior Table
    4. 6.4 Device Functioning Modes
      1. 6.4.1 Flash Mode
      2. 6.4.2 Torch Mode
      3. 6.4.3 IR Mode
      4. 6.4.4 Voltage Mode
      5. 6.4.5 Mode Transitions
      6. 6.4.6 Boost Operation
        1. 6.4.6.1 Start-Up (Enabling The Device)
        2. 6.4.6.2 Pass Mode
        3. 6.4.6.3 Output Voltage Regulation
    5. 6.5 Programming and Control
      1. 6.5.1 Dx_EN Bits
      2. 6.5.2 STR1 and STR2 Usage
      3. 6.5.3 TOR/TX Usage
      4. 6.5.4 Control State Diagram
      5. 6.5.5 I2C-Compatible Interface
        1. 6.5.5.1 Data Validity
        2. 6.5.5.2 Start and Stop Conditions
        3. 6.5.5.3 Transferring Data
        4. 6.5.5.4 I2C-Compatible Chip Address
    6. 6.6 Register Descriptions
      1. 6.6.1 MainReg Registers
  8. 7 Application and Implementation
    1. 7.1 Application Information
    2. 7.2 Typical Application
      1. 7.2.1 Design Requirements
      2. 7.2.2 Output Control Examples
        1. 7.2.2.1 Four Channel Flash with Strobe1 Trigger Starting in Standby
        2. 7.2.2.2 Four Channel Flash with Strobe1 Trigger Starting in I2C Torch
        3. 7.2.2.3 Mixed Mode Functionality
        4. 7.2.2.4 Voltage Mode Only
        5. 7.2.2.5 Voltage Mode With Advanced IR
      3. 7.2.3 Detailed Design Procedure
        1. 7.2.3.1 Snubber Requirement
        2. 7.2.3.2 Output Capacitor Selection
        3. 7.2.3.3 Input Capacitor Selection
        4. 7.2.3.4 Inductor Selection
      4. 7.2.4 Application Curves
  9. 8 Power Supply Recommendations
  10. 9 Layout
    1. 9.1 Layout Guidelines
    2. 9.2 Layout Example
  11. 10Device and Documentation Support
    1. 10.1 Third-Party Products Disclaimer
    2. 10.2 Receiving Notification of Documentation Updates
    3. 10.3 Support Resources
    4. 10.4 Trademarks
    5. 10.5 Electrostatic Discharge Caution
    6. 10.6 Glossary
  12. 11Revision History
  13. 12Mechanical, Packaging, and Orderable Information

Package Options

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

6.5.2 STR1 and STR2 Usage

Two external synchronization Strobe pins are available to enable the four LED outputs in either Flash or IR mode. Each of the four outputs can be assigned to either Strobe pin via the Strobe Control Register (bits [7:0] in reg 0x03). Each output assigned to a strobe pin must be set to the same LED mode, either all Flash or all IR. Additionally, no output should be assigned to both strobe pins. If D1 is assigned to STR1, it should not be assigned to STR2 as well.

If the LM3645 is already enabled, the minimum strobe duration in either level or edge mode must be 10 µs. This restriction applies to both flash and IR mode operation. If the LM3645 is in standby and either strobe pin is asserted, it is recommended that the strobe duration be no less than 1ms to ensure that the boost has enough time to reach the proper level to ensure current into the LED can regulate.

Note:

It is recommended that the STR1 and STR2 pins be held low before enabling the outputs assigned to each strobe pin.

Table 6-3 Strobe Control Truth Table
STRx ENSTRx PinDx ModeAction
XXOffOff
0XIRIR PreCharge Mode, I2C
0XFlashFlash, I2C
10IRIR PreCharge Mode, I2C
11IRIR Current Pulse Mode, Strobe Controlled
10FlashOff
11FlashFlash, Strobe Controlled