SNLA267A March   2019  – June 2019 DS90UB953-Q1 , DS90UB954-Q1 , DS90UB960-Q1

 

  1.   How to Design a FPD-Link III System Using DS90UB953-Q1 and DS90UB954-Q1
    1.     Trademarks
    2. 1 Overview
      1. 1.1 System Level Functionality
    3. 2 Basic Design Rules
      1. 2.1 IDX and MODE Pin Verification
        1. 2.1.1 REF Clock, CLK IN, AON and Frequency Selection
          1. 2.1.1.1 Synchronous Mode
          2. 2.1.1.2 Non-Synchronous CLK_IN Mode
          3. 2.1.1.3 Non-Synchronous AON Mode
          4. 2.1.1.4 CSI Throughput
          5. 2.1.1.5 Clocking and Frequency Selection Example
      2. 2.2 Successful I2C Communication With 953 and 954
        1. 2.2.1 Aliasing
        2. 2.2.2 Port Selection on 954
      3. 2.3 I2C Passthrough Verification
      4. 2.4 Basic Diagnostic and Error Registers
    4. 3 Designing the Link Between SER and DES
      1. 3.1 Back Channel Configuration
      2. 3.2 BIST
        1. 3.2.1 BIST Configuration and Status
        2. 3.2.2 BIST Procedure
        3. 3.2.3 List of Registers Used in BIST Script
      3. 3.3 AEQ
      4. 3.4 CML Out
    5. 4 Designing Link Between SER and Image Sensor
      1. 4.1 Sensor Initialization Using SER GPIOs
      2. 4.2 CLKOUT
    6. 5 Designing Link Between DES and ISP
      1. 5.1 Frame Sync
        1. 5.1.1 Using SER GPIOs From the DES
        2. 5.1.2 Internal and External Frame Sync Configuration
        3. 5.1.3 Tables for Using GPIOs and Frame Sync
      2. 5.2 Port Forwarding
      3. 5.3 Pattern Generation
        1. 5.3.1 Accessing Indirect Registers
        2. 5.3.2 Pattern Generation From DES to ISP and SER to DES
    7. 6 Hardware Design
      1. 6.1 Basic I2C Connectors
        1. 6.1.1 I2C Pullups for SDA and SCL
      2. 6.2 AC Capacitor on FPD3 Link
      3. 6.3 Capacitance Used in Loop Filter
      4. 6.4 Critical Signal Routing
      5. 6.5 Time Domain Reflection
      6. 6.6 Return Loss and Insertion Loss
      7. 6.7 Power-over-Coax (PoC)
      8. 6.8 Voltage and Temperature Sensing
    8. 7 Appendix
      1. 7.1 Scripts
        1. 7.1.1  BIST Script
        2. 7.1.2  Example Sensor Initialization Script
        3. 7.1.3  CSI Enable and Port Forwarding Script
        4. 7.1.4  Enabling CMLOUT FPD3 RX Port 0 on 954
        5. 7.1.5  Remote Enabled SER GPIO Toggle Script
        6. 7.1.6  Local SER GPIO Toggle Script
        7. 7.1.7  Internal FrameSync on 953 GPIO1
        8. 7.1.8  External FrameSync on 953 GPIO0
        9. 7.1.9  SER GPIOs as Inputs and Output to DES GPIO
        10. 7.1.10 Pattern Generation on the 953 Script
        11. 7.1.11 Pattern Generation on the 954 Script
        12. 7.1.12 Monitor Errors for Predetermined Time Script
        13. 7.1.13 954 and 953 CSI Register Check Script
        14. 7.1.14 Time Till Lock Script on 953
      2. 7.2 Acknowledgments
  2.   Revision History

6.6 Return Loss and Insertion Loss

When talking about loss, it is important to consider cables, the Power-over-Coax circuit on each side of the SERDES system, the connectors, the layout, and the AEQ settings.

Insertion Loss simply refers to the amount of loss that occurs when a signal is sent across the transmission line. We want the insertion loss to be as close to 0 dB as possible—which means minimal loss. The DS90UB954-Q1 has an adaptive equalizer at the input, which allows the device to compensate for various lengths of cable, provided the total attenuation stays within maximum allowable limits.

Return Loss is the loss of the signal power resulting from a discontinuity in the characteristic impedance of the transmission line. In other words, when signal is sent across the transmission channel, an amount of the signal will be reflected and returned back to the transmitter. It is most commonly encountered at the interface of one portion of the transmission line and another–such as the connector to a cable or board. Return Loss has been historically represented in dB. If the engineer wants to minimize the reflection of the signal, return loss must be as small as possible. This is usually represented by larger negative numbers in dB.

When discussing coax cables, it is important to note that a coax cable can be designed to be arbitrarily thin, and therefore low-cost and flexible. However, as the cable gets thinner, the losses increase. Inline Connectors also add loss to the signal. The frequency characteristics of inline connector loss differ from cables, and can often be considered as relatively flat across frequency. Connector manufacturers will specify the loss of their connectors, but typical FAKRA connectors have a loss of 0.1 to 0.2 dB per connector.