SNLS398H January   2012  – February 2018 DS125DF410

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Typical Application Diagram
  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 Device Data Path Operation
      2. 7.3.2 Signal Detect
      3. 7.3.3 CTLE
      4. 7.3.4 DFE
      5. 7.3.5 Clock and Data Recovery
      6. 7.3.6 Output Driver
      7. 7.3.7 Device Configuration
        1. 7.3.7.1 Rate and Subrate Setting
    4. 7.4 Device Functional Modes
      1. 7.4.1 SMBus Master Mode and SMBus Slave Mode
      2. 7.4.2 Address Lines <ADDR_[3:0]>
      3. 7.4.3 SDA and SDC
      4. 7.4.4 Standards-Based Modes
        1. 7.4.4.1 Ref_mode 3 Mode (Reference Clock Required)
        2. 7.4.4.2 False Lock Detector Setting
        3. 7.4.4.3 Reference Clock In
        4. 7.4.4.4 Reference Clock Out
        5. 7.4.4.5 Driver Output Voltage
        6. 7.4.4.6 Driver Output De-Emphasis
        7. 7.4.4.7 Driver Output Rise/Fall Time
        8. 7.4.4.8 INT
        9. 7.4.4.9 LOCK_3, LOCK_2, LOCK_1, and LOCK_0
    5. 7.5 Programming
      1. 7.5.1  SMBus Strap Observation
      2. 7.5.2  Device Revision and Device ID
      3. 7.5.3  Control/Shared Register Reset
      4. 7.5.4  Interrupt Channel Flag Bits
      5. 7.5.5  SMBus Master Mode Control Bits
      6. 7.5.6  Resetting Individual Channels of the Retimer
      7. 7.5.7  Interrupt Status
      8. 7.5.8  Overriding the CTLE Boost Setting
      9. 7.5.9  Overriding the VCO Search Values
      10. 7.5.10 Overriding the Output Multiplexer
      11. 7.5.11 Overriding the VCO Divider Selection
      12. 7.5.12 Using the PRBS Generator
      13. 7.5.13 Using the Internal Eye Opening Monitor
      14. 7.5.14 Overriding the DFE Tap Weights and Polarities
      15. 7.5.15 Enabling Slow Rise/Fall Time on the Output Driver
      16. 7.5.16 Inverting the Output Polarity
      17. 7.5.17 Overriding the Figure of Merit for Adaptation
      18. 7.5.18 Setting the Rate and Subrate for Lock Acquisition
      19. 7.5.19 Setting the Adaptation/Lock Mode
      20. 7.5.20 Initiating Adaptation
      21. 7.5.21 Setting the Reference Enable Mode
      22. 7.5.22 Overriding the CTLE Settings Used for CTLE Adaptation
      23. 7.5.23 Setting the Output Differential Voltage
      24. 7.5.24 Setting the Output De-Emphasis Setting
    6. 7.6 Register Maps
      1. 7.6.1 Register Information
      2. 7.6.2 Bit Fields in the Register Set
      3. 7.6.3 Writing to and Reading from the Control/Shared Registers
      4. 7.6.4 Channel Select Register
      5. 7.6.5 Reading to and Writing from the Channel Registers
  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
      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 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Trademarks
    3. 11.3 Electrostatic Discharge Caution
    4. 11.4 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

7.3.3 CTLE

The CTLE in the DS125DF410 is a fully adaptive equalizer with optional limiting stage. The CTLE adapts according to a Figure of Merit (FOM) calculation during the lock acquisition process.

Once the CDR has locked and the CTLE has been adapted, the CTLE boost level will be frozen until a manual re-adapt command is issued or until the CDR re-enters the lock acquisition state. The CTLE is typically readapted by resetting the CDR.

The CTLE consists of 4 stages, with each stage having 2-bit boost control. This allows for 256 different stage-boost combinations. The CTLE adaption algorithm allows the CTLE to adapt through 32 of these stage-boost combinations. These 32 stage-boost combinations comprise the EQ Table in the channel registers; see channel registers 0x40 through 0x5F. This EQ Table can be reprogrammed to support up to 32 of the 256 stage-boost settings.

CTLE boost levels are determined by summing the boosts levels of the 4 stages. Different stage-boost combinations that sum to the same number will have approximately the same boost level, but will result in a different shape for the EQ transfer function (boost curve).

The fourth stage in the CTLE can be programmed through the SMBus interface to become a limiting stage rather than a linear stage. This is useful in some applications, but it should not be typically used in combination with the DFE.