SNVS598B August   2010  – March 2018 LM3535

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Typical Application
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin 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 Charge Pump
      2. 7.3.2 Diode Current Sinks
      3. 7.3.3 Ambient Light Sensing (ALS) And Interrupt
      4. 7.3.4 Dynamic Backlight Control Input (PWM Pin)
      5. 7.3.5 LED Forward Voltage Monitoring
      6. 7.3.6 Configurable Gain Transition Delay
      7. 7.3.7 Hardware Enable (HWEN)
    4. 7.4 Device Functional Modes
      1. 7.4.1 Shutdown
      2. 7.4.2 Standby
      3. 7.4.3 Active Mode
    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
        5. 7.5.1.5 Internal Registers of LM3535
  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 Ambient Light Sensing
          1. 8.2.2.1.1 Ambient Light Sensor Block
          2. 8.2.2.1.2 ALS Operation
            1. 8.2.2.1.2.1 ALS Configuration Example
          3. 8.2.2.1.3 ALS Averaging Time
          4. 8.2.2.1.4 Ambient Light Current Control + PWM
            1. 8.2.2.1.4.1 ALS + PWM Example
        2. 8.2.2.2 LED Configurations
        3. 8.2.2.3 Maximum Output Current, Maximum LED Voltage, Minimum Input Voltage
          1. 8.2.2.3.1 Total Output Current Capability
        4. 8.2.2.4 Parallel Connected and Unused Outputs
        5. 8.2.2.5 Power Efficiency
        6. 8.2.2.6 Power Dissipation
        7. 8.2.2.7 Thermal Protection
        8. 8.2.2.8 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 Receiving Notification of Documentation Updates
    2. 11.2 Community Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

8.2.2.5 Power Efficiency

Efficiency of LED drivers is commonly taken to be the ratio of power consumed by the LEDs (PLED) to the power drawn at the input of the part (PIN). With a 3/2× – 1× charge pump, the input current is equal to the charge pump gain times the output current (total LED current). The efficiency of the LM3535 can be predicted as follow:

Equation 10. PLEDTOTAL = (VLEDA × NA × ILEDA) + (VLEDB × NB × ILEDB) + (VLEDC × ILEDC)
Equation 11. PIN = VIN × IIN
Equation 12. PIN = VIN × (GAIN × ILEDTOTAL + IQ)
Equation 13. E = (PLEDTOTAL / PIN)

The LED voltage is the main contributor to the charge-pump gain selection process. Use of low forward-voltage LEDs (3 V to 3.5 V) allows the LM3535 to stay in the gain of 1× for a higher percentage of the lithium-ion battery voltage range when compared to the use of higher forward voltage LEDs (3.5 V to 4 V). See LED Forward Voltage Monitoring for a more detailed description of the gain selection and transition process.

For an advanced analysis, TI recommends that power consumed by the circuit (VIN x IIN) for a given load be evaluated rather than power efficiency.