TIDUF06 August   2022

 

  1.   Description
  2.   Resources
  3.   Features
  4.   Applications
  5.   5
  6. 1System Description
    1. 1.1 Key System Specifications
  7. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
      1. 2.2.1 PCB and Form Factor
      2. 2.2.2 Power Supply Design
        1. 2.2.2.1 POC Filter
        2. 2.2.2.2 Power Supply Considerations
          1. 2.2.2.2.1 Choosing External Components
          2. 2.2.2.2.2 Choosing the Buck 1 Inductor
          3. 2.2.2.2.3 Choosing the Buck 2 and Buck 3 Inductors
          4. 2.2.2.2.4 Functional Safety
    3. 2.3 Highlighted Products
      1. 2.3.1 DS90UB953-Q1
      2. 2.3.2 TPS650330-Q1
      3. 2.3.3 IMX623
    4. 2.4 System Design Theory
  8. 3Hardware, Testing Requirements, and Test Results
    1. 3.1 Required Hardware
      1. 3.1.1 Hardware Setup
      2. 3.1.2 FPD-Link III I2C Initialization
      3. 3.1.3 IMX623 Initialization
    2. 3.2 Testing and Results
      1. 3.2.1 Test Setup
        1. 3.2.1.1 Power Supplies Startup
        2. 3.2.1.2 Power Supply Startup – 1.8 V Rail and Serializer PDB Setup
      2. 3.2.2 Test Results
        1. 3.2.2.1 Power Supplies Start Up
        2. 3.2.2.2 Power Supply Output Voltage Ripple
        3. 3.2.2.3 Power Supply Load Currents
        4. 3.2.2.4 I2C Communications
  9. 4Design Files
    1. 4.1 Schematics
    2. 4.2 Bill of Materials
    3. 4.3 PCB Layout Recommendations
      1. 4.3.1 PMIC Layout Recommendations
      2. 4.3.2 PCB Layer Stackup
      3. 4.3.3 Serializer Layout Recommendations
      4. 4.3.4 Imager Layout Recommendations
      5. 4.3.5 Layout Prints
    4. 4.4 Altium Project
    5. 4.5 Gerber Files
    6. 4.6 Assembly Drawings
  10. 5Related Documentation
  11. 6Trademarks

2.4 System Design Theory

The main design challenges to consider for automotive cameras are size, ease of use, and thermal efficiency. Automotive cameras are often placed in remote regions of the vehicle where area is limited, requiring an overall compact solution. Because of this, the system is designed around having the lowest number of components with a fully-integrated PMIC power solution. As ADAS applications continue to grow in capability and complexity, the increase in demand for automotive cameras requires that ease of use, or flexibility, becomes another critical factor to reduce system design cycle and time-to-market. The choice of the DS90UB953-Q1 and TPS650330-Q1 devices are important here as they are compatible with a wide range of imagers. The choice of a two-board solution highlights this flexibility, as the power and serializer base board can be re-used with different imager boards depending on the ADAS application. Additionally, the Sony® IMX623 image sensor is selected as part of a family of pin-compatible automotive image sensors: IMX622, ISX021, and ISX031. The option for NOR flash is included on the IMX623 imager board to enable compatibility with the ISX021 and ISX031 devices. Lastly, the small size and remote placement of these cameras increases their susceptibility to heat. A power efficient system is crucial to preserve the image quality in these conditions. The TPS650330-Q1 device is optimized for efficiency with a three buck and one LDO regulator topology, enabling the support of medium and high quality imagers without sacrificing thermal performance. Due to the impact of thermals on the system performance, it is important to calculate total system efficiency as part of the design process. From the Buck 1 output power in Table 2-2 and assuming an efficiency of 85%, Equation 2 calculates a system input power of about 1.5 W. Equation 6 can then be used with the output power of Buck 2, Buck 3, and the LDO to calculate the overall system efficiency.

Equation 6. ηSYSTEM=POUTPIN=POUT, Buck 2+POUT, Buck 3+POUT, LDOPIN, Buck 1=73%