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  • LM36922H Highly Efficient Dual-String White LED Driver

    • SNVSAF2A February   2016  – February 2016 LM36922H

      PRODUCTION DATA.  

  • CONTENTS
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  • LM36922H Highly Efficient Dual-String White LED Driver
  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 I2C 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 Enabling the LM36922H
        1. 7.3.1.1 Current Sink Enable
      2. 7.3.2 LM36922H Start-Up
      3. 7.3.3 Brightness Mapping
        1. 7.3.3.1 Linear Mapping
        2. 7.3.3.2 Exponential Mapping
      4. 7.3.4 PWM Input
        1. 7.3.4.1 PWM Sample Frequency
          1. 7.3.4.1.1 PWM Resolution and Input Frequency Range
          2. 7.3.4.1.2 PWM Sample Rate and Efficiency
            1. 7.3.4.1.2.1 PWM Sample Rate Example
        2. 7.3.4.2 PWM Hysteresis
        3. 7.3.4.3 PWM Step Response
        4. 7.3.4.4 PWM Timeout
      5. 7.3.5 LED Current Ramping
      6. 7.3.6 Regulated Headroom Voltage
    4. 7.4 Device Functional Modes
      1. 7.4.1 Brightness Control Modes
        1. 7.4.1.1 I2C Only (Brightness Mode 00)
        2. 7.4.1.2 PWM Only (Brightness Mode 01)
        3. 7.4.1.3 I2C + PWM Brightness Control (Multiply Then Ramp) Brightness Mode 10
        4. 7.4.1.4 I2C + PWM Brightness Control (Ramp Then Multiply) Brightness Mode 11
      2. 7.4.2 Boost Switching Frequency
        1. 7.4.2.1 Minimum Inductor Select
      3. 7.4.3 Auto-Switching Frequency
      4. 7.4.4 I2C Address Select (ASEL)
      5. 7.4.5 Fault Protection/Detection
        1. 7.4.5.1 Overvoltage Protection (OVP)
          1. 7.4.5.1.1 Case 1 OVP Fault Only (OVP Threshold Hit and All Enabled Current Sink Inputs > 40 mV)
          2. 7.4.5.1.2 Case 2a OVP Fault and Open LED String Fault (OVP Threshold Occurrence and Any Enabled Current Sink Input ≤ 40 mV)
          3. 7.4.5.1.3 Case 2b OVP Fault and Open LED String Fault (OVP Threshold Duration and Any Enabled Current Sink Input ≤ 40 mV)
          4. 7.4.5.1.4 OVP/LED Open Fault Shutdown
          5. 7.4.5.1.5 Testing for LED String Open
        2. 7.4.5.2 Voltage Limitations on LED1, LED2
        3. 7.4.5.3 LED String Short Fault
        4. 7.4.5.4 Overcurrent Protection (OCP)
          1. 7.4.5.4.1 OCP Fault
          2. 7.4.5.4.2 OCP Shutdown
        5. 7.4.5.5 Device Overtemperature
          1. 7.4.5.5.1 Overtemperature Shutdown
    5. 7.5 Programming
      1. 7.5.1 I2C Interface
        1. 7.5.1.1 Start and Stop Conditions
        2. 7.5.1.2 I2C Address
        3. 7.5.1.3 Transferring Data
        4. 7.5.1.4 Register Programming
    6. 7.6 Register Maps
  8. 8 Applications 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 Component Selection
          1. 8.2.2.1.1 Inductor
          2. 8.2.2.1.2 Output Capacitor
          3. 8.2.2.1.3 Input Capacitor
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
    1. 9.1 Input Supply Bypassing
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 Boost Output Capacitor Placement
      2. 10.1.2 Schottky Diode Placement
      3. 10.1.3 Inductor Placement
      4. 10.1.4 Boost Input Capacitor Placement
    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 Trademarks
    3. 11.3 Community Resources
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information
  13. IMPORTANT NOTICE
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DATA SHEET

LM36922H Highly Efficient Dual-String White LED Driver

1 Features

  • 1% Matched Current Sinks Across Process, Voltage, Temperature
  • 3% Current-Sink Accuracy Across Process, Voltage, Temperature
  • 11-Bit Dimming Resolution
  • Up to 90% Solution Efficiency
  • Drives from One to Two Parallel LED Strings at up to 38 V at 25 mA per String
  • PWM Dimming Input
  • I2C Programmable
  • Selectable 500-kHz and 1-MHz Switching Frequency With Optional –12% shift
  • Auto Switch Frequency Mode (250 kHz, 500 kHz, 1 MHz)
  • Four Configurable Overvoltage Protection Thresholds (17 V, 24 V, 31 V, 38 V)
  • Four Configurable Overcurrent Protection Thresholds (750 mA, 1000 mA, 1250 mA,
    1500 mA)
  • Thermal Shutdown Protection
  • Externally Selectable I2C Address Options via ASEL Input

2 Applications

  • Power Source for Smart Phone and Tablet Backlighting
  • LCD Panels With up to 24 LEDs

3 Description

The LM36922H is an ultra-compact, highly efficient, two-string white-LED driver designed for LCD display backlighting. The device can power up to 12 series LEDs at up to 25 mA per string. An adaptive current regulation method allows for different LED voltages in each string while maintaining current regulation.

The LED current is adjusted via an I2C interface or through a logic level PWM input. The PWM duty cycle is internally sensed and mapped to an 11-bit current thus allowing for a wide range of PWM frequencies with noise-free operation from 50 µA to 25 mA.

Other features include an auto-frequency mode, which can automatically change the frequency based on load current in order to optimize efficiency.

The device operates over the 2.5-V to 5.5-V input voltage range and a –40°C to +85°C temperature range.

Device Information(1)

PART NUMBER PACKAGE BODY SIZE (MAX)
LM36922H DSBGA (12) 1.756 mm × 1.355 mm
  1. For all available packages, see the orderable addendum at the end of the data sheet.

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Simplified Schematic

LM36922H typapp_snvsaf2.gif

Typical String-to-String Matching vs LED Current

LM36922H MATCH_CODE.png

4 Revision History

Changes from * Revision (February 2016) to A Revision

  • Changed device from product preview to production Go

5 Pin Configuration and Functions

YFF Package
12-Pin DSBGA
Top View
LM36922H pin_diagram_36932.gif

Pin Functions

PIN I/O DESCRIPTION
NUMBER NAME
A1 LED1 Input Input to current sink 1. The boost converter regulates the minimum voltage between LED1, LED2 to VHR.
A2 ASEL Input ASEL is a logic input which selects between two I2C address options. This pin is read on power up (VIN going above 1.8 V, and HWEN going above a logic high voltage). GND = address 0x36, logic high = address 0x37.
A3 GND Input Ground
B1 LED2 Input Input pin to current sink 2. The boost converter regulates the minimum voltage between LED1, LED2 to VHR.
B2 SDA I/O Data I/O for I2C-Compatible Interface.
B3 SW Output Drain connection for internal low side NFET, and anode connection for external Schottky diode.
C1 NC Input Unused pin. Connect externally to GND.
C2 SCL Input Clock input for I2C-compatible interface.
C3 OUT Input OUT serves as the sense point for overvoltage protection. Connect OUT to the positive pin of the output capacitor.
D1 PWM Input Logic level input for PWM current control.
D2 HWEN Input Hardware enable input. Drive HWEN high to bring the device out of shutdown and allow I2C writes or PWM control.
D3 IN Input Input voltage connection. Bypass IN to GND with a minimum 2.2-µF ceramic capacitor.

 
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