ZHCSME1C August   2018  – June 2021 DS250DF230

PRODUCTION DATA  

  1. 1 特性
  2. 2 应用
  3. 3 说明
  4. 4 Revision History
  5. 5 说明（续）
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Timing Requirements
    7. 7.7 Switching Characteristics
    8. 7.8 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1  Device Data Path Operation
      2. 8.3.2  Signal Detect
      3. 8.3.3  Continuous Time Linear Equalizer (CTLE)
      4. 8.3.4  Variable Gain Amplifier (VGA)
      5. 8.3.5  Cross-Point Switch
      6. 8.3.6  Decision Feedback Equalizer (DFE)
      7. 8.3.7  Clock and Data Recovery (CDR)
        1. 8.3.7.1 CDR Bypass (Raw) Mode
        2. 8.3.7.2 CDR Fast Lock Mode
      8. 8.3.8  Calibration Clock
      9. 8.3.9  Differential Driver With FIR Filter
        1. 8.3.9.1 Setting the Output VOD, Pre-Cursor, and Post-Cursor Equalization
        2. 8.3.9.2 Output Driver Polarity Inversion
        3. 8.3.9.3 Slow Slew Rate
      10. 8.3.10 Debug Features
        1. 8.3.10.1 Pattern Generator
        2. 8.3.10.2 Pattern Checker
        3. 8.3.10.3 Eye-Opening Monitor
      11. 8.3.11 Interrupt Signals
    4. 8.4 Device Functional Modes
      1. 8.4.1 Supported Data Rates
      2. 8.4.2 SMBus Master Mode
      3. 8.4.3 Device SMBus Address
    5. 8.5 Programming
      1. 8.5.1 Bit Fields in the Register Set
      2. 8.5.2 Writing to and Reading from the Global/Shared/Channel Registers
    6. 8.6 Register Maps
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Applications
      1. 9.2.1 Front-Port Jitter Cleaning Applications
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
        3. 9.2.1.3 Application Curves
      2. 9.2.2 Active Cable Applications
        1. 9.2.2.1 Design Requirements
        2. 9.2.2.2 Detailed Design Procedure
        3. 9.2.2.3 Application Curves
      3. 9.2.3 Backplane and Mid-Plane Applications
        1. 9.2.3.1 Design Requirements
        2. 9.2.3.2 Detailed Design Procedure
        3. 9.2.3.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Examples
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Development Support
    2. 12.2 Documentation Support
      1. 12.2.1 Related Documentation
    3. 12.3 接收文档更新通知
    4. 12.4 支持资源
    5. 12.5 Trademarks
  13. 13Electrostatic Discharge Caution
  14. 14术语表
  15. 15Mechanical, Packaging, and Orderable Information

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8.3.7 Clock and Data Recovery (CDR)

The CDR consists of a Phase-Locked Loop (PLL), PPM counter, and Input and Output Data Multiplexers (mux) that allow for retimed data, non-retimed data, a PRBS generator, and output muted modes.

By default, the equalized data is fed into the CDR for clock and data recovery. The recovered data is then output to the FIR filter and differential driver together with the recovered clock that was cleaned of any high-frequency jitter outside the bandwidth of the CDR clock recovery loop. The bandwidth of the CDR defaults to 4.7 MHz (typical) in full-rate (divide-by-1) mode and 4 MHz (typical) in sub-rate mode. The CDR bandwidth is adjustable. Refer to the DS250DF230 Programmer's Guide (SNLU182) for more information on adjusting the CDR bandwidth. Users can configure the CDR data to route the recovered clock and data to the PRBS checker. Users also have the option of configuring the output of the CDR to send raw non-retimed data, or data from the pattern generator.

The CDR requires these items for proper configuration:

  • A 30.72-MHz or 25-MHz calibration clock to run the PPM counter (CAL_CLK_IN).
  • Expected data rates must be programmed into the CDR either through the rate table or entered manually with the corrected divider settings. Refer to the DS250DF230 Programmer's Guide (SNLU182) for more information on configuring the CDR for different data rates.

The DS250DF230 offers a low-speed recovered clock for channel 0. This feature is useful for the cases when recovered clock from FPGA or ASIC has in-band spurs on the phase noise plot because of the digital switching noise. See the Table 8-6 for the recovered clock frequency versus input data rate.