SNLS686 February   2021 DS160PR421

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and 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 DC Electrical Characteristics
    6. 6.6 High Speed Electrical Characteristics
    7. 6.7 SMBUS/I2C Timing Charateristics
    8. 6.8 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 Linear Equalization
      2. 7.3.2 Flat Gain
      3. 7.3.3 Receiver Detect State Machine
    4. 7.4 Device Functional Modes
      1. 7.4.1 Active PCIe Mode
      2. 7.4.2 Active Buffer Mode
      3. 7.4.3 Standby Mode
    5. 7.5 Programming
      1. 7.5.1 Control and Configuration Interface
        1. 7.5.1.1 Pin Mode
          1. 7.5.1.1.1 Four-Level Control Inputs
        2. 7.5.1.2 SMBUS/I2C Register Control Interface
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 PCIe x8 Lane Switching
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
        3. 8.2.1.3 Pin-to-pin Passive versus Redriver Option
        4. 8.2.1.4 Application Curves
      2. 8.2.2 DisplayPort Application
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
  11. 11Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Receiving Notification of Documentation Updates
    2. 12.2 Support Resources
    3. 12.3 Trademarks
    4. 12.4 Electrostatic Discharge Caution
    5. 12.5 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

8.2.1.2 Detailed Design Procedure

In PCIe Gen 4.0 and Gen 3.0 applications, the specification requires Rx-Tx link training to establish and optimize signal conditioning settings at 16 Gbps and 8 Gbps, respectively. In link training, the Rx partner requests a series of FIR – pre-shoot and de-emphasis coefficients (10 Presets) from the Tx partner. The Rx partner includes 7-levels (6 dB to 12 dB) of CTLE followed by a single tap DFE. The link training would pre-condition the signal, with an equalized link between the root-complex and endpoint.

Note that there is no link training in PCIe Gen 1.0 (2.5 Gbps) or PCIe Gen 2.0 (5.0 Gbps) applications. The DS160PR421 is placed in between the Tx and Rx. It helps extend the PCB trace reach distance by boosting the attenuated signals with its equalization, which allows the user to recover the signal by the downstream Rx more easily.

For operation in Gen 4.0 and Gen 3.0 links, the DS160PR421 transmit outputs are designed to pass the Tx Preset signaling onto the Rx for the PCIe Gen 4.0 or Gen 3.0 link to train and optimize the equalization settings. The suggested setting for the device is GAIN = L3 (default). Adjustments to the EQ setting should be performed based on the channel loss to optimize the eye opening in the Rx partner. The Tx equalization presets or CTLE and DFE coefficients in the Rx can also be adjusted to further improve the eye opening.