SNLS144K June   2005  – March 2024 DS40MB200

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Ratings
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
    6. 5.6 Switching Characteristics
    7. 5.7 Typical Characteristics
  7. 6 Parameter Measurement Information
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 CML Inputs and EQ
      2. 7.3.2 Multiplexer and Loopback Control
      3. 7.3.3 CML Drivers and Pre-Emphasis Control
  9. 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
  10. 9 Power Supply Recommendations
  11. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Examples
  12. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Support Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  13. 12Revision History
  14. 13Mechanical, Packaging, and Orderable Information

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7.3.3 CML Drivers and Pre-Emphasis Control

The output driver has pre-emphasis (driver-side equalization) to compensate the transmission loss of the backplane that it is driving. The driver conditions the output signal such that the lower frequency and higher frequency pulses reach approximately the same amplitude at the end of the backplane and minimize the deterministic jitter caused by the amplitude disparity. The DS40MB200 provides four steps of user-selectable pre-emphasis ranging from 0, –3, –6 and –9 dB to handle different lengths of backplane. Figure 7-2 shows a driver pre-emphasis waveform. The pre-emphasis duration is 200 ps nominal, corresponding to 0.8 unit intervals (UI) at 4Gbps. The pre-emphasis levels of switch-side and line-side can be individually programmed.

DS40MB200 Driver Pre-Emphasis Differential Waveform (Showing All 4 Pre-Emphasis Steps)Figure 7-2 Driver Pre-Emphasis Differential Waveform (Showing All 4 Pre-Emphasis Steps)
Table 7-3 Line-Side Pre-Emphasis Controls
PreL_[1:0]PRE-EMPHASIS LEVEL IN mVPP
(VODB)		DE-EMPHASIS LEVEL IN mVPP
(VODPE)		PRE-EMPHASIS IN dB
(VODPE/VODB)		TYPICAL FR4
BOARD TRACE
0 012001200010 inches
0 11200850−320 inches
1 01200600−630 inches
1 1
(default)		1200426−940 inches
Table 7-4 Switch-Side Pre-Emphasis Controls
PreS_[1:0]PRE-EMPHASIS LEVEL IN mVPP
(VODB)		DE-EMPHASIS LEVEL IN mVPP
(VODPE)		PRE-EMPHASIS IN dB
(VODPE/VODB)		TYPICAL FR4
BOARD TRACE
0 012001200010 inches
0 11200850−320 inches
1 01200600−630 inches
1 1
(default)		1200426−940 inches