SPRACN9F May   2023  – August 2024 AM67 , AM67A , AM68 , AM68A , AM69 , AM69A , DRA821U , DRA821U-Q1 , DRA829J , DRA829J-Q1 , DRA829V , DRA829V-Q1 , TDA4AEN-Q1 , TDA4AH-Q1 , TDA4AL-Q1 , TDA4AP-Q1 , TDA4VE-Q1 , TDA4VEN-Q1 , TDA4VH-Q1 , TDA4VL-Q1 , TDA4VM , TDA4VM-Q1 , TDA4VP-Q1

 

  1.   1
  2.   Jacinto7 AM6x/TDA4x/DRA8x LPDDR4 Design Guidelines
  3.   Trademarks
  4. 1Overview
    1. 1.1 Supporting Documentation
    2. 1.2 Board Designs Supported
    3. 1.3 General Board Layout Guidelines
    4. 1.4 PCB Stack-Up
    5. 1.5 Bypass Capacitors
      1. 1.5.1 Bulk Bypass Capacitors
      2. 1.5.2 High-Speed Bypass Capacitors
    6. 1.6 Velocity Compensation
  5. 2LPDDR4 Board Design and Layout Guidance
    1. 2.1  LPDDR4 Introduction
    2. 2.2  LPDDR4 Device Implementations Supported
    3. 2.3  LPDDR4 Interface Schematics
    4. 2.4  Compatible JEDEC LPDDR4 Devices
    5. 2.5  Placement
    6. 2.6  LPDDR4 Keepout Region
    7. 2.7  Net Classes
    8. 2.8  LPDDR4 Signal Termination
    9. 2.9  LPDDR4 VREF Routing
    10. 2.10 LPDDR4 VTT
    11. 2.11 CK, CMD_ADDR, and CTRL Topologies
    12. 2.12 Data Group Topologies
    13. 2.13 CK, CMD_ADDR, and CTRL Routing Specification
    14. 2.14 Data Group Routing Specification
    15. 2.15 Channel, Byte, and Bit Swapping
  6. 3LPDDR4 Board Design Simulations
    1. 3.1 Board Model Extraction
    2. 3.2 Board-Model Validation
    3. 3.3 S-Parameter Inspection
    4. 3.4 Time Domain Reflectometry (TDR) Analysis
    5. 3.5 Simulation Integrity Analysis
      1. 3.5.1 Simulation Setup
      2. 3.5.2 Simulation Parameters
      3. 3.5.3 Simulation Targets
        1. 3.5.3.1 Waveform Quality
        2. 3.5.3.2 Eye Quality
        3. 3.5.3.3 Delay Report
        4. 3.5.3.4 Mask Report
    6. 3.6 Design Example
      1. 3.6.1 Stack-Up
      2. 3.6.2 Routing
      3. 3.6.3 Model Verification
      4. 3.6.4 Simulation Results
  7. 4Revision History

3.1 Board Model Extraction

The board level extraction guidelines listed below are intended to work in any EDA extraction tool and are not tool-specific. It is important to follow the steps outlined in Section 3.2 through Section 3.4 immediately after completing touchstone model extractions. The design should be checked with these steps prior to running IBIS simulations.

  1. For DDR extractions, extract power (VDDS_DDR/VDDQ and VDDS_DDR_BIAS/VDDQX) and signal nets together in a 3D-EM solver. For SerDes extractions power is not required as the simulations are only intended for Signal Integrity
  2. Use wide-band models. It is recommended to extract from DC to at least till 6x the Nyquist frequency (for example, for LPDDR4-4266 extract the model at least till 12.8 GHz).
  3. Check the board stack-up for accurate layer thickness and material properties.
    1. It is recommended to use Djordjevic-Sarkar models for the dielectric material definition.
  4. Use accurate etch profiles and surface roughness for the signal traces across all layers in the stack-up.
  5. If the board layout is cut prior to extraction (to reduce simulation time), please define a cut boundary that is at least 0.25 inch away from the signal and power nets.
  6. Check the via padstack definitions.
    1. Ensure that the non-functional internal layer pads on signal vias are modeled the same way they would be fabricated.
    2. These non-functional internal layer pads on signal vias are not recommended by TI.
  7. Use Spice/S-parameter models (typically available from the vendor) for modeling all passives in the system