SPRAD06B March   2022  – November 2024 AM620-Q1 , AM623 , AM625 , AM625-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Overview
    1. 1.1 Board Designs Supported
    2. 1.2 General Board Layout Guidelines
    3. 1.3 PCB Stack-Up
    4. 1.4 Bypass Capacitors
      1. 1.4.1 Bulk Bypass Capacitors
      2. 1.4.2 High-Speed Bypass Capacitors
      3. 1.4.3 Return Current Bypass Capacitors
    5. 1.5 Velocity Compensation
  5. 2DDR4 Board Design and Layout Guidance
    1. 2.1  DDR4 Introduction
    2. 2.2  DDR4 Device Implementations Supported
    3. 2.3  DDR4 Interface Schematics
      1. 2.3.1 DDR4 Implementation Using 16-Bit SDRAM Devices
      2. 2.3.2 DDR4 Implementation Using 8-Bit SDRAM Devices
    4. 2.4  Compatible JEDEC DDR4 Devices
    5. 2.5  Placement
    6. 2.6  DDR4 Keepout Region
    7. 2.7  DBI
    8. 2.8  VPP
    9. 2.9  Net Classes
    10. 2.10 DDR4 Signal Termination
    11. 2.11 VREF Routing
    12. 2.12 VTT
    13. 2.13 POD Interconnect
    14. 2.14 CK and ADDR_CTRL Topologies and Routing Guidance
    15. 2.15 Data Group Topologies and Routing Guidance
    16. 2.16 CK and ADDR_CTRL Routing Specification
      1. 2.16.1 CACLM - Clock Address Control Longest Manhattan Distance
      2. 2.16.2 CK and ADDR_CTRL Routing Limits
    17. 2.17 Data Group Routing Specification
      1. 2.17.1 DQLM - DQ Longest Manhattan Distance
      2. 2.17.2 Data Group Routing Limits
    18. 2.18 Bit Swapping
      1. 2.18.1 Data Bit Swapping
      2. 2.18.2 Address and Control Bit Swapping
  6. 3LPDDR4 Board Design and Layout Guidance
    1. 3.1  LPDDR4 Introduction
    2. 3.2  LPDDR4 Device Implementations Supported
    3. 3.3  LPDDR4 Interface Schematics
    4. 3.4  Compatible JEDEC LPDDR4 Devices
    5. 3.5  Placement
    6. 3.6  LPDDR4 Keepout Region
    7. 3.7  LPDDR4 DBI
    8. 3.8  Net Classes
    9. 3.9  LPDDR4 Signal Termination
    10. 3.10 LPDDR4 VREF Routing
    11. 3.11 LPDDR4 VTT
    12. 3.12 CK0 and ADDR_CTRL Topologies
    13. 3.13 Data Group Topologies
    14. 3.14 CK0 and ADDR_CTRL Routing Specification
    15. 3.15 Data Group Routing Specification
    16. 3.16 Byte and Bit Swapping
  7. 4LPDDR4 Board Design Simulations
    1. 4.1 Board Model Extraction
    2. 4.2 Board-Model Validation
    3. 4.3 S-Parameter Inspection
    4. 4.4 Time Domain Reflectometry (TDR) Analysis
    5. 4.5 System Level Simulation
      1. 4.5.1 Simulation Setup
      2. 4.5.2 Simulation Parameters
      3. 4.5.3 Simulation Targets
        1. 4.5.3.1 Eye Quality
        2. 4.5.3.2 Delay Report
        3. 4.5.3.3 Mask Report
    6. 4.6 Design Example
      1. 4.6.1 Stack-Up
      2. 4.6.2 Routing
      3. 4.6.3 Model Verification
      4. 4.6.4 Simulation Results
  8. 5Appendix: AM62x ALW and AMC Package Delays
  9. 6Revision History

3.10 LPDDR4 VREF Routing

LPDDR4 memories generate their own VREFCA and VREFDQ internally for the address / command bus and data bus, respectively. Similarly, the DDR PHY also provides its own reference voltage for the data group nets during reads. Thus unlike DDR3 and DDR4, VREF does not need to be generated on the board, and there is no required VREF routing for an LPDDR4 configuration.