SBOS681C July   2014  – November 2017 OPT3001


  1. Features
  2. Applications
    1.     Spectral Response: The OPT3001 and Human Eye
  3. Description
    1.     Block Diagram
  4. Revision History
  5. Pin Configuration and Functions
    1.     Pin Functions
  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 Timing Requirements
    7. 6.7 Typical Characteristics
  7. Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Human Eye Matching
      2. 7.3.2 Automatic Full-Scale Range Setting
      3. 7.3.3 Interrupt Operation, INT Pin, and Interrupt Reporting Mechanisms
      4. 7.3.4 I2C Bus Overview
        1. Serial Bus Address
        2. Serial Interface
    4. 7.4 Device Functional Modes
      1. 7.4.1 Automatic Full-Scale Setting Mode
      2. 7.4.2 Interrupt Reporting Mechanism Modes
        1. Latched Window-Style Comparison Mode
        2. Transparent Hysteresis-Style Comparison Mode
        3. End-of-Conversion Mode
        4. End-of-Conversion and Transparent Hysteresis-Style Comparison Mode
    5. 7.5 Programming
      1. 7.5.1 Writing and Reading
        1. High-Speed I2C Mode
        2. General-Call Reset Command
        3. SMBus Alert Response
    6. 7.6 Register Maps
      1. 7.6.1 Internal Registers
        1. Register Descriptions
          1. Result Register (offset = 00h)
            1. Table 7. Result Register Field Descriptions
          2. Configuration Register (offset = 01h) [reset = C810h]
            1. Table 10. Configuration Register Field Descriptions
          3. Low-Limit Register (offset = 02h) [reset = C0000h]
            1. Table 11. Low-Limit Register Field Descriptions
          4. High-Limit Register (offset = 03h) [reset = BFFFh]
            1. Table 13. High-Limit Register Field Descriptions
          5. Manufacturer ID Register (offset = 7Eh) [reset = 5449h]
            1. Table 14. Manufacturer ID Register Field Descriptions
          6. Device ID Register (offset = 7Fh) [reset = 3001h]
            1. Table 15. Device ID Register Field Descriptions
  8. Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Electrical Interface
      2. 8.1.2 Optical Interface
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. Optomechanical Design
        2. Dark Window Selection and Compensation
      3. 8.2.3 Application Curves
    3. 8.3 Do's and Don'ts
  9. Power-Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Community Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information
    1. 12.1 Soldering and Handling Recommendations
    2. 12.2 DNP (S-PDSO-N6) Mechanical Drawings



Dark Window Selection and Compensation

There are several approaches to selecting and compensating for a dark window. One of many approaches is the method described here.

Sample several different windows with various levels of darkness. Choose a window that is dark enough to optimize the balance between the aesthetics of the device and sensor performance. Note that the aesthetic evaluation is the subjective opinion of the designer; therefore, it is more important to see the window on the physical design rather than refer to window transmission specifications on paper. Make sure that the chosen window is not darker than absolutely necessary because a darker window allows less light to illuminate the sensor and therefore impedes sensor accuracy.

The window chosen for this application example is dark and has less than 7% transmission at 550 nm.Figure 31 shows the normalized response of the spectrum. Note that the equipment used to measure the transmission spectrum is not capable of measuring the absolute accuracy (non-normalized) of the dark window sample, but only the relative normalized spectrum. Also note that the window is much more transmissive to infrared wavelengths longer than 700 nm than to visible wavelengths between 400 nm and 650 nm. This imbalance between infrared and visible light decreases the ratio of visible light to infrared light at the sensor. Although it is preferable to have the window decrease this ratio as little as possible (by having a window with a close ratio of visible transmission to infrared transmission), the OPT3001 still performs well as shown in Figure 34.

OPT3001 D018_SBOS681.gifFigure 31. Normalized Transmission Spectral Response of the Chosen Dark Window

After choosing the dark window, measure the attenuating effect of the dark window for later compensation. In order to measure this attenuation, measure a fluorescent light source with a lux meter, then measure that same light with the OPT3001 under the dark window. To measure accurately, it is important to use a fixture that can accommodate either the lux meter or the design containing the OPT3001 and dark window, with the center of each of the sensing areas being in exactly the same X, Y, Z location, as shown in Figure 32. The Z placement of the design (distance from the light source) is the top of the window, and not the OPT3001 itself.

OPT3001 aij_Measurement_Fixture.gifFigure 32. Fixture with One Light Source Accommodating Either a Lux Meter or the Design (Window and OPT3001) in the Exact Same X,Y,Z Position

The fluorescent light in this location measures 1000 lux with the lux meter, and 73 lux with the OPT3001 under the dark window within the application. Therefore, the window has an effective transmission of 7.3% for the fluorescent light. This 7.3% is the weighted average attenuation across the entire spectrum, weighted by the spectral response of the lux meter (or photopic response).

For all subsequent OPT3001 measurements under this dark window, the following formula is applied.

Equation 5. Compensated Measurement = Uncompensated Measurement / (7.3%)