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

8.2.2.1.2 ALS Operation

The ambient light sensor input has a 0 to 1 V operational input voltage range. The Specifications shows the LM3535 with an ambient light sensor (AVAGO, APDS-9005) and the internal ALS Resistor Select Register set to 0x40 (2.32 kΩ). This circuit converts 0 to 1000 LUX light into approximately a 0 to 850 mV linear output voltage. The voltage at the active ambient light sensor input is compared against the 8 bit values programmed into the Zone Boundary Registers (ZB0-ZB3). When the ambient light sensor output crosses one of the ZB0 – ZB3 programmed thresholds the internal ALS circuitry will smoothly transition the LED current to the new 7 bit brightness level as programmed into the appropriate Zone Target Register (Z0T – Z4T, see Figure 28).

With bits [6:4] of the Configuration Register set to 1 (Bit6 = ALS Block Enable, Bit5 = BankB ALS Enable, Bit4 = BankA ALS Enable), the LM3535 is configured for ambient light current Control. In this mode the ambient light sensing input (ALS) monitors the output of analog output ambient light sensing photo diode and adjusts the LED current depending on the ambient light. The ambient light sensing circuit has 4 configurable ambient light boundaries (ZB0 – ZB3) programmed through the four (8-bit) Zone Boundary Registers. These zone boundaries define 5 ambient brightness zones.

On start-up the 4 Zone Boundary Registers are pre-loaded with 0x33 (51d), 0x66 (102d), 0x99 (153d), and 0xCC (204d). The ALS input has a 1-V active input voltage range which makes the default Zone Boundaries approx. set at:

Zone Boundary 0 = 200 mV

Zone Boundary 1 = 400 mV

Zone Boundary 2 = 600 mV

Zone Boundary 3 = 800 mV

These Zone Boundary Registers are all 8-bit (readable and writable) registers. By default, the first zone (Z0) is defined between 0 and 200 mV, default for Z1 is defined between 200 mV and 400 mV, Z2 is defined between 400 mV and 600 mV, Z3 is defined between 600 mV and 800 mV, and Z4 is defined between 800 mV and 1 V. The default settings for the 5 Zone Target Registers are 0x19, 0x33, 0x4C, 0x66, and 0x7F. This corresponds to LED brightness settings of 84 µA, 164 µA, 1.45 mA, 6.17 mA and 25 mA of current, respectively. See Figure 31.

LM3535 30082443.gifFigure 31. ALS Zone to LED Brightness Mapping