SNLS456D March   2016  – October 2019 DS250DF410

PRODUCTION DATA.  

  1. Features
  2. Applications
  3. Description
    1.     Device Images
      1.      Simplified Schematic
  4. Revision History
  5. Description (continued)
  6. Pin Configuration and Functions
    1.     Pin Functions
  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, Retimer Jitter Specifications
    7. 7.7  Timing Requirements, Retimer Specifications
    8. 7.8  Timing Requirements, Recommended Calibration Clock Specifications
    9. 7.9  Recommended SMBus Switching Characteristics (Slave Mode)
    10. 7.10 Recommended SMBus Switching Characteristics (Master Mode)
    11. 7.11 Recommended JTAG Switching Characteristics
    12. 7.12 Typical Characteristics
  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)
      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
      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
      12. 8.3.12 JTAG Boundary Scan
    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. 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 Example
  12. 12Device and Documentation Support
    1. 12.1 Documentation Support
      1. 12.1.1 Development Support
    2. 12.2 Documentation Support
      1. 12.2.1 Related Documentation
    3. 12.3 Receiving Notification of Documentation Updates
    4. 12.4 Support Resources
    5. 12.5 Trademarks
    6. 12.6 Electrostatic Discharge Caution
    7. 12.7 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

Eye Opening Monitor

The DS250DF410’s Eye Opening Monitor (EOM) measures the internal data eye at the input of the decision slicer and can be used for 2 functions:

  1. Horizontal Eye Opening (HEO) and Vertical Eye Opening (VEO) measurement
  2. Full Eye Diagram Capture

The HEO measurement is made at the 0V crossing and is read in channel register 0x27. The VEO measurement is made at the 0.5 UI mark and is read in channel register 0x28. The HEO and VEO registers can be read from channel registers 0x27 and 0x28 at any time while the CDR is locked. The following equations are used to convert the contents of channel registers 0x27 and 0x28 into their appropriate units:

  • HEO [UI] = Reg_0x27 ÷ 32
  • VEO [mV] = Reg_0x28 x 3.125

A full eye diagram capture can be performed when the CDR is locked. The eye diagram is constructed within a 64 x 64 array, where each cell in the matrix consists of an 16-bit word representing the total number of hits recorded at that particular phase and voltage offset. Users can manually adjust the vertical scaling of the EOM or allow the state machine to control the scaling which is the default option. The horizontal scaling controlled by the state machine and is always directly proportional to the data rate.

When a full eye diagram plot is captured, the retimer will shift out four 16-bit words of residual data that should be discarded followed by 4096 16-bit words that make up the 64 × 64 eye plot. The first actual word of the eye plot from the retimer is for (X, Y) position (0,0), which is the earliest position in time and the most negative position in voltage. Each time the eye plot data is read out the voltage position is incremented. Once the voltage position has incremented to position 63 (the most positive voltage), the next read will cause the voltage position to reset to 0 (the most negative voltage) and the phase position to increment. This process will continue until the entire 64 × 64 matrix is read out. Figure 14 below shows the EOM read out sequence overlaid on top of a simple eye opening plot. In this plot any hits are shown in green. This type of plot is helpful for quickly visualizing the HEO and VEO. Users can apply different algorithms to the output data to plot density or color gradients to the output data.

DS250DF410 EOM_Full_Eye_Capture_Readout.gifFigure 14. EOM Full Eye Capture Readout

To manually control the EOM vertical range, remove scaling control from the state machine then select the desired range:

Channel Reg 0x2C[6] → 0 (see Table 3).

Table 3. Eye Opening Monitor Vertical Range Settings

CH REG 0x11[7:6] VALUE EOM VERTICAL RANGE [mV]
2’b00 ±100
2'b01 ±200
2'b10 ±300
2'b11 ±400

The EOM operates as an under-sampled circuit. This allows the EOM to be useful in identifying over equalization, ringing and other gross signal conditioning issues. However, the EOM cannot be correlated to a bit error rate.

The EOM can be accessed in two ways to read out the entire eye plot:

  • Multi-byte reads can be used such that data is repeatedly latched out from channel register 0x25.
  • With single byte reads, the MSB are located in register 0x25 and the LSB are located in register 0x26. In this mode, the device must be addressed each time a new byte is read.

To perform a full eye capture with the EOM, follow these steps below within the desired channel register set:

Table 4. Eye Opening Monitor Full Eye Capture Instructions

STEP REGISTER [bits] Operation VALUE DESCRIPTION
1 0x67[5] Write 0 Disable lock EOM lock monitoring
2 0x2C[6] Write 0 Set the desired EOM vertical range
0x11[7:6] Write 2'b--
3 0x11[5] Write 0 Power on the EOM
4 0x24[7] Write 1 Enable fast EOM
5 0x24[0]
0x25
0x26
Read 1 Begin read out of the 64 x 64 array, discard first 4 words
Ch reg 0x24[0] is self-clearing.
0x25 is the MSB of the 16-bit word
0x26 is the LSB of the 16-bit word
6 0x25 Read Continue reading information until the 64 x 64 array is complete.
0x26
7 0x67[5] Write 1 Return the EOM to its original state. Undo steps 1-4
0x2C[6] Write 1
0x11[5] Write 1
0x24[7] Write 0