Table Of Content

PCB Design for External DDR Memory 80-VT310-10 Rev. A Confidential and Proprietary –Qualcomm Technologies, Inc. Restricted Distribution: Not to be distributed to anyone who is not an employee of either Qualcomm or its subsidiaries without the express approval of Qualcomm’s Configuration Management. Confidential and Proprietary –Qualcomm Technologies, Inc. NO PUBLIC DISCLOSURE PERMITTED: Please report postings of this document on public servers or websites to: [email protected]. Restricted Distribution: Not to be distributed to anyone who is not an employee of either Qualcomm or its subsidiaries without the express approval of Qualcomm’s Configuration Management. Not to be used, copied, reproduced, or modified in whole or in part, nor its contents revealed in any manner to others without the express written permission of Qualcomm Technologies, Inc. Qualcomm is a trademark of QUALCOMM Incorporated, registered in the United States and other countries. All QUALCOMM Incorporatedtrademarks are used with permission. MSM is a trademark of Qualcomm Incorporated, registered in the United States and other countries. Other product and brand names may be trademarks or registered trademarks of their respective owners. This technical data may be subject to U.S. and international export, re-export, or transfer (“export”) laws. Diversion contrary to U.S. and international law is strictly prohibited. Qualcomm Technologies, Inc. 5775 Morehouse Drive San Diego, CA 92121 U.S.A. © 2014 Qualcomm Technologies, Inc. Confidential and Proprietary –Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-10 Rev. A 2 Revision History Revision Date Description A October 2014 Initial release Confidential and Proprietary –Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-10 Rev. A 3 Agenda 1 Overview 6 2 Introduction to the Memory Interface 9 3 PCB Memory Bus Design Guidelines 18 4 PCB Design Example 59 5 Frequently Asked Questions (FAQ) 82 Confidential and Proprietary –Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-10 Rev. A 4 Terms and Definitions Term Definition Processor Qualcomm Technologies, Inc. (QTI) ICs – MSM™, APQ, MPQ, and MDM Controller QTI ICs – MSM, APQ, MPQ, and MDM. Controllers drive the bus in WRITE mode. DRAM DRAM memory IC packages. DRAM drives the bus in READ mode. DDR; LPDDR Double data rate and lower power double data rate memory standard. Reference plane The metal plane closest to a signal trace. It is a GND plane most of the time, but can be a power plane too. Confidential and Proprietary –Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-10 Rev. A 5 Section 1 Overview Confidential and Proprietary –Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-10 Rev. A 6 Scope and Intended Audience This document is intended for engineers who are designing with QTI devices driving the LPDDR2/LPDDR3 external memory interface. This document describes the fundamental DDR memory channel, and demonstrates PCB design techniques and strategies that lead to better signal integrity performance. Sec. 1 Confidential and Proprietary –Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-10 Rev. A 7 Section 2 Introduction to the Memory Interface Confidential and Proprietary –Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-10 Rev. A 8 External Memory Interface for Mobile Devices The CPU needs memory to store, access, and compute data.  DRAM components provide high data bandwidth to enable fast data access.  DDR and LPDDR  DDR is used mostly for PCs. VDDQ = 1.8 V, 1.5 V, and 1.35 V  LPDDR was created for mobile devices to reduce power consumption. VDDQ = 1.2 V  PoP memory, stacked memory, and external memory  This document only covers the external memory bus design.  PoP memory package Stacked die memory package Sec. 2 Confidential and Proprietary –Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-10 Rev. A 9 External Memory Interface Example for Mobile Devices Sec. 2 Confidential and Proprietary –Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-10 Rev. A 10