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

8.2.2.1.2.1 ALS Configuration Example

As an example, assume that the APDS-9005 is used as the ambient light sensing photo diode with its output connected to the ALS input. The ALS Resistor Select Register (Address 0x51) is loaded with 0x40 which configures the ALS input for a 2.32-kΩ internal pulldown resistor (see Table 2). This gives the output of the APDS-9005 a typical voltage swing of 0 to 875mV with a 0 to 1k LUX change in ambient light (0.875mV/Lux). Next, the Configuration Register (Address 0x20) is programmed with 0xDC, the ALS Control Register (Address 0x50) programmed to 0x40 and the Control Register is programmed to 0x3F . This configures the device ALS interface for:

  • Ambient Light Current Control for BankA enabled
  • ALS circuitry enabled
  • Assigns D53 and D62 to bankA
  • Sets the ALS Averaging Time to 400 ms

Next, the Control Register (Address 0x10) is programmed with 0x3F which enables the 6 LEDs via the I2C-compatible interface.

Now assume that the APDS-9005 ambient light sensor detects a 100 LUX ambient light at its input. This forces the ambient light sensor output (and the ALS input) to 87.5 mV corresponding to Zone 0. Since Zone 0 points to the brightness code programmed in Zone Target Register 0 (loaded with code 0x19), the LED current becomes:

Equation 2. LM3535 30082444.gif

Next assume that the ambient light changes to 500 LUX (corresponding to an ALS voltage of 437.5 mV). This moves the ambient light into Zone 2 which corresponds to Zone Target Register 2 (loaded with code 0x4C) the LED current then becomes:

Equation 3. LM3535 30082445.gif