SPRAD06C March   2022  – March 2025 AM620-Q1 , AM623 , AM625 , AM625-Q1 , AM62L

 

  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. 5Additional Information: Package Delays
  9. 6Summary
  10. 7References
  11. 8Revision History

4.6.1 Stack-Up

These guidelines recommend a 8- or 6-layer PCB stack-up for full device entitlement. Below are 8- and 6-layer example stack-ups:

  • Designs using FR4 products like 370HR are supported, but also recommend higher speed materials like ISOLA I-Speed (or equivalent) for increased margin. IT180A is also another material to help with cost vs. performance tradeoffs
  • These examples routes all data groups on layer 3. While this minimizes the via travel and, therefore, reduces via-to-via coupling, but leaves a longer via stub.
  • These examples routes all CA signals on the bottom layer.
Table 4-4 Example 8-layer PCB Stackup for LPDDR4 (PROC124 AM62x LP SK EVM)
Layer No Stackup Routing Plan Highest Priorities and Layer
Solder mask
1 TOP - SIG/PWR BGA breakouts, GND, DRAM decoupling capacitors
2 GND Solid GND reference plane
3 SIG/PWR LPDDR4 Data, VDD1_LPDDR4_1V8, LVCMOS escape
4 PWR VDD_LPDDR4 (under SOC and LPDDR4), SOC_DVDD1V8, VDDA_1V8
5 PWR VDD_CORE, SOC_DVDD3V3, VCC_3V3_SYS, VPP_1V8, VDDA_1V8_OSC
6 SIG LVCMOS escape
7 GND Solid GND reference plane
8 BOTTOM - SIG/PWR LPDDR4 CA, LVCMOS escape, SOC decoupling capacitors, GND, DRAM decaps
Solder mask
Table 4-5 Example 6-layer PCB Stackup for LPDDR4 (PROC181 AM62Lx EVM)
Layer No Stackup Routing Plan Highest Priorities and Layer
Solder mask
1 TOP - SIG/PWR BGA breakouts, VDD_LPDDR4 to DRAM, VDD_LPDDR4 bulk capacitors
2 GND Solid GND reference plane
3 SIG/PWR LPDDR4 Data, LVCMOS escape, SOC_DVDD3V3, SOC_DVDD1V8, VDDA_1V8
4 PWR VDD_CORE, VDD_LPDDR4 (under SOC and LPDDR4), VDDA_1V8
5 GND Solid GND reference plane
6 SIG/PWR LPDDR4 CA, LVCMOS escape, SOC/DRAM decoupling capacitors, VDD1_LPDDR4_1V8, DRAM test points
Solder mask