SPRACN9E september   2022  – may 2023 AM67 , AM67A , AM68 , AM68A , AM69 , AM69A , DRA829J , DRA829J-Q1 , DRA829V , DRA829V-Q1 , TDA4AEN-Q1 , TDA4VEN-Q1 , TDA4VM , TDA4VM-Q1

 

  1.   1
  2.   Jacinto 7 LPDDR4 Board Design and Layout Guidelines
  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
    5. 1.5 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 and ADDR_CTRL Topologies
    12. 2.12 Data Group Topologies
    13. 2.13 CK and ADDR_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

3.5.1 Simulation Setup

Set up the system-level schematic in the simulator by connecting the SOC IBIS model, board model, power supplies, DRAM package model, and DRAM IBIS model. A typical system-level DDR schematic is shown in Figure 3-2.

Note:

Be aware of the DRAM configuration (number of dies in the package, number of ranks, and number of channels) while setting up the system schematic.

Be aware the DRAM configuration may also include On-Die Decoupling Circuit.

GUID-0E4E6649-F0F8-4D4F-AC1C-8AA9BABE760B-low.png Figure 3-2 Typical System-Level DDR Schematic
  • LPDDR4 simulations require power-aware IBIS models for the controller and the memory along with a simulator that supports channel simulations for DDR interfaces.
  • SPICE-based transistor-level simulations cannot be used for generating BER signal eyes. Use a simulator that can handle power-aware IBIS simulations and can run channel simulations for the DDR interface.
  • IBIS models reduce simulation time with minimal loss in accuracy compared with SPICE-based transistor-level simulations. IBIS models starting from version 5.0 are power-aware models which enables Simultaneous Switching Output (SSO) noise simulations. The TI IBIS model is a power-aware IBIS model.
  • Use SPICE models to accurately model the on-die decoupling capacitance on the DDR supply net for both – controller and DRAM. This ensures accurate power noise and Power Supply Induced Jitter (PSIJ) estimation in DDR simulations. The on-die decoupling capacitance information for the DRAM can be obtained from the DRAM vendor.
  • Use SPICE or S-parameter files to model the DRAM package. This can be requested from the DRAM vendor. EBD models are not recommended.
  • J7ES model for the on-die decoupling capacitance on the DDR supply net: 
    ******************************************
* On-die Decoupling circuit for J7ES (DIE_VDDS_DDR to VSS)
******************************************
* Notes:
* Includes on-die decoupling for all DDR signals 
*
* This subcircuit should be added across the J7ES IBIS model's
* DIE_VDDS_DDR and VSS pins
*
******************************************
* x_decouple DIE_VDDS_DDR vss_die J7ES_ondie_decoupling_alldq
******************************************
.SUBCKTJ7ES_ondie_decoupling_alldq DIE_VDDS_DDR vss_die
Cvddq_c  DIE_VDDS_DDR DIE_VDDS_DDR_c 2105.86e-12
Rvddq_c  vss_die DIE_VDDS_DDR_c 43e-3
.ENDS