SPRABI1D January   2018  – July 2022 66AK2E05 , 66AK2G12 , 66AK2H06 , 66AK2H12 , 66AK2H14 , 66AK2L06 , AM5K2E02 , AM5K2E04 , SM320C6678-HIREL , TMS320C6652 , TMS320C6654 , TMS320C6655 , TMS320C6657 , TMS320C6670 , TMS320C6671 , TMS320C6672 , TMS320C6674 , TMS320C6678

 

  1.   Trademarks
  2. 1 Introduction
  3. 2 Background
  4. 3 Migrating Designs From DDR2 to DDR3 (Features and Comparisons)
    1. 3.1 Topologies
      1. 3.1.1 Balanced Line Topology
        1. 3.1.1.1 Balanced Line Topology Issues
      2. 3.1.2 Fly-By Topology
        1. 3.1.2.1 Balanced Line Topology Issues
    2. 3.2 ECC (Error Correction)
    3. 3.3 DDR3 Features and Improvements
      1. 3.3.1 Read Leveling
      2. 3.3.2 Write Leveling
      3. 3.3.3 Pre-fetch
      4. 3.3.4 ZQ Calibration
      5. 3.3.5 Reset Pin Functionality
      6. 3.3.6 Additional DDR2 to DDR3 Differences
  5. 4 Prerequisites
    1. 4.1 High Speed Designs
    2. 4.2 JEDEC DDR3 Specification – Compatibility and Familiarity
    3. 4.3 Memory Types
    4. 4.4 Memory Speeds
    5. 4.5 Addressable Memory Space
    6. 4.6 DDR3 SDRAM/UDIMM Memories, Topologies, and Configurations
      1. 4.6.1 Topologies
      2. 4.6.2 Configurations
        1. 4.6.2.1 Memories – SDRAM Selection Criteria
    7. 4.7 DRAM Electrical Interface Requirements
      1. 4.7.1 Slew
      2. 4.7.2 Overshoot and Undershoot Specifications
        1. 4.7.2.1 Overshoot and Undershoot Example Calculations
      3. 4.7.3 Typical DDR3 AC and DC Characteristics
      4. 4.7.4 DDR3 Tolerances and Noise – Reference Signals
  6. 5 Package Selection
    1. 5.1 Summary
      1. 5.1.1 ×4 SDRAM
      2. 5.1.2 ×8 SDRAM
      3. 5.1.3 ×16 SDRAM
      4. 5.1.4 ×32 SDRAM
      5. 5.1.5 ×64 SDRAM
  7. 6 Physical Design and Implementation
    1. 6.1 Electrical Connections
      1. 6.1.1 Pin Connectivity and Unused Pins – SDRAM Examples
      2. 6.1.2 Pin Connectivity – ECC UDIMM and Non-ECC UDIMM Examples
    2. 6.2 Signal Terminations
      1. 6.2.1 External Terminations – When Using Read and Write Leveling
      2. 6.2.2 External Terminations – When Read and Write Leveling is Not Used
      3. 6.2.3 Internal Termination – On-Die Terminations
      4. 6.2.4 Active Terminations
      5. 6.2.5 Passive Terminations
      6. 6.2.6 Termination Component Selection
    3. 6.3 Mechanical Layout and Routing Considerations
      1. 6.3.1 Routing Considerations – SDRAMs
        1. 6.3.1.1  Mechanical Layout – SDRAMs
        2. 6.3.1.2  Stack Up – SDRAMs
        3. 6.3.1.3  Routing Rules – General Overview (SDRAMs)
        4. 6.3.1.4  Routing Rules – Address and Command Lines (SDRAMs)
        5. 6.3.1.5  Routing Rules – Control Lines (SDRAMs)
        6. 6.3.1.6  Routing Rules – Data Lines (SDRAMs)
        7. 6.3.1.7  Routing Rules – Clock Lines (SDRAMs)
        8. 6.3.1.8  Routing Rules – Power (SDRAMs)
        9. 6.3.1.9  Write Leveling Limit Impact on Routing – KeyStone I
        10. 6.3.1.10 Round-Trip Delay Impact on Routing – KeyStone I
        11. 6.3.1.11 Write Leveling Limit Impact on Routing – KeyStone II
        12. 6.3.1.12 Round-Trip Delay Impact on Routing – KeyStone II
      2. 6.3.2 Routing Considerations – UDIMMs
        1. 6.3.2.1 Mechanical Layout – UDIMMs
        2. 6.3.2.2 Stack Up – UDIMMs
        3. 6.3.2.3 Routing Rules – General Overview (UDIMMs)
        4. 6.3.2.4 Routing Rules – Address and Command Lines (UDIMMs)
        5. 6.3.2.5 Routing Rules – Control Lines (UDIMMs)
        6. 6.3.2.6 Routing Rules – Data Lines (UDIMMs)
        7. 6.3.2.7 Routing Rules – Clock Lines (UDIMMs)
        8. 6.3.2.8 Routing Rules – Power (UDIMMs)
        9. 6.3.2.9 Write-Leveling Limit Impact on Routing
    4. 6.4 Timing Considerations
    5. 6.5 Impedance Considerations
      1. 6.5.1 Routing Impedances – KeyStone I Devices
        1. 6.5.1.1 Data Group Signals
        2. 6.5.1.2 Fly-By Signals
      2. 6.5.2 Routing Impedances – KeyStone II Devices
        1. 6.5.2.1 Data Group Signals
        2. 6.5.2.2 Fly-By Signals
      3. 6.5.3 Comparison to JEDEC UDIMM Impedance Recommendations
    6. 6.6 Switching and Output Considerations
  8. 7 Simulation and Modeling
    1. 7.1 Simulation and Modeling
    2. 7.2 Tools
    3. 7.3 Models
    4. 7.4 TI Commitment
  9. 8 Power
    1. 8.1 DDR3 SDRAM Power Requirements
      1. 8.1.1 Vref Voltage Requirements
      2. 8.1.2 VTT Voltage Requirements
    2. 8.2 DSP DDR3 Power Requirements
    3. 8.3 DDR3 Power Estimation
    4. 8.4 DSP DDR3 Interface Power Estimation
    5. 8.5 Sequencing – DDR3 and DSP
  10. 9 Disclaimers
  11. 10References
  12. 11Revision History

6.3.2.9 Write-Leveling Limit Impact on Routing

The write-leveling process in the DDR3 interface imposes an upper and lower limit on the maximum and minimum skew between the command delay and the data delay. If this limit is exceeded, the DDR3 interface may fail the write leveling process and data corruption may occur. This limit is sufficiently large so that well-controlled topologies will not likely exceed the limit.

The same write-leveling limits in KeyStone I designs outlined for SDRAMs in Section 6.3.1.9 also apply to UDIMMS. Any calculations performed must take both board and UDIMM routing into consideration.