SBAS704B June   2015  – October 2015 OPT8241

PRODUCTION DATA.  

  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 Timing Requirements
    7. 6.7 Switching Characteristics
    8. 6.8 Optical Characteristics
    9. 6.9 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 Output Block
        1. 7.3.1.1 Serializer and LVDS Output Interface
        2. 7.3.1.2 Parallel CMOS Output Interface
      2. 7.3.2 Temperature Sensor
    4. 7.4 Device Functional Modes
    5. 7.5 Programming
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 Presence Detection for Industrial Safety
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Frequencies of Operation
          2. 8.2.1.2.2 Number of Sub-Frames and Quads
          3. 8.2.1.2.3 Field of View (FoV)
          4. 8.2.1.2.4 Lens
          5. 8.2.1.2.5 Integration Duty Cycle
          6. 8.2.1.2.6 Design Summary
        3. 8.2.1.3 Application Curve
      2. 8.2.2 People Counting and Locating
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
          1. 8.2.2.2.1 Frequencies of Operation
          2. 8.2.2.2.2 Number of Sub-Frames and Quads
          3. 8.2.2.2.3 Field of View (FoV)
          4. 8.2.2.2.4 Lens
          5. 8.2.2.2.5 Integration Duty Cycle
          6. 8.2.2.2.6 Design Summary
        3. 8.2.2.3 Application Curve
      3. 8.2.3 People Locating and Identification
        1. 8.2.3.1 Design Requirements
        2. 8.2.3.2 Detailed Design Procedure
          1. 8.2.3.2.1 Frequencies of Operation
          2. 8.2.3.2.2 Number of Sub-Frames and Quads
          3. 8.2.3.2.3 Field of View (FoV)
          4. 8.2.3.2.4 Lens
          5. 8.2.3.2.5 Integration Duty Cycle
          6. 8.2.3.2.6 Design Summary
        3. 8.2.3.3 Application Curve
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 MIX Supply Decapacitors
      2. 10.1.2 LVDS Transmitters
      3. 10.1.3 Optical Centering
      4. 10.1.4 Image Orientation
      5. 10.1.5 Thermal Considerations
    2. 10.2 Layout Example
    3. 10.3 Mechanical Assembly Guidelines
      1. 10.3.1 Board-Level Reliability
      2. 10.3.2 Handling
  11. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
    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

10 Layout

10.1 Layout Guidelines

10.1.1 MIX Supply Decapacitors

The VMIXH supply has a peak load current requirement of approximately 600 mA during the integration phase. Moreover, a break-before-make circuit is used during the reversal of the demodulation polarity to avoid high through currents. The break-before-make strategy results in a pulse with a drop and a subsequent rise of demodulation current. The pulse duration is typically approximately 1 ns. In order to effectively support the rise in currents, VMIXH decoupling capacitors must be placed very close to the package. Furthermore, use multiple capacitors to reduce the effect of equivalent series inductance and resistance of the decoupling capacitors. Use a combination of 10-nF and 1-nF capacitors per VMIXH pin. Using vias for routing the trace from decoupling capacitors to the package pins must be avoided.

10.1.2 LVDS Transmitters

Each LVDS data output pair must be routed as a 100-Ω differential pair. When used with the OPT9221, 100-Ω termination resistors must be placed close to the OPT9221.

10.1.3 Optical Centering

The lens mount placement on the printed circuit board (PCB) must be such that the lens optical center aligns with the pixel array optical center. Note that the pixel array center is different from the package center.

10.1.4 Image Orientation

The sensor orientation for obtaining an upright image is shown in Figure 18.

OPT8241 snsor_orntn_fr_uprght_img_sbas704.gif Figure 18. Sensor Orientation for Obtaining an Upright Image

10.1.5 Thermal Considerations

In some applications, special care must be taken to avoid high sensor temperatures because demodulation power is considerably high for the size of the package. Lower sensor temperatures help lower the thermal noise floor as well as reduce the leakage currents. Two recommended methods for achieving better package to PCB thermal coupling are listed below:

  • Use a thermal pad below the sensor on both sides of the PCB with stitched vias.
  • Use a compatible underfill.

10.2 Layout Example

OPT8241 layout_eg_sbas704.png Figure 19. Example Layout

10.3 Mechanical Assembly Guidelines

10.3.1 Board-Level Reliability

TI chip-on-glass products are designed and tested with underfill to ensure excellent board-level reliability in intended applications. If a customer chooses to underfill a chip-on-glass product, following the guidelines below is recommended to maximize the board level reliability:

  • The underfill material must extend partially up the package edges. Underfill that ends at the bottom (ball side) of the die degrades reliability.
  • The underfill material must have a coefficient of thermal expansion (CTE) closely matched to the CTE of the solder interconnect.
  • The underfill material must have a glass transition temperature (Tg) above the expected maximum exposure temperature.
Thermoset ME-525 is a good example of a compatible underfill.

10.3.2 Handling

To avoid dust particles on the sensor, the sensor tray must only be opened in a cleanroom facility. In case of accidental exposure to dust, the recommended method to clean the sensors is to use an IPA solution with a micro-fiber cloth swab with no lint. Do not handle the sensor edges with hard or abrasive materials (such as metal tweezers) because the sensor package has a glass outline. Such handling may lead to cracks that can negatively affect package reliability and image quality.