Systems & Design

LPDDR4/4X DRAM Variants and Possible System Configurations

What LPDDR4/4X DRAMs are available and what are the different possible system configurations with such DRAMs?


LPDDR is the de-facto standard for main-memory targeting mobile applications such as smartphones and tablets. Low-Power Double Data Rate Synchronous Dynamic Random Access Memories (LPDDR SDRAMs) or DRAMS offer high-performance while consuming significantly lower power than standard DDR memories, such as DDR5/4/3, which are ideal for systems requiring large memory capacity. For this reason, LPDDR DRAMs are ideal for applications that do not require large DRAM capacity, but need high bandwidth and are sensitive to power even when the system is in a standby mode. Some of the key features of LPDDR4/4X DRAMs are shown in Figure 1. While LPDDR4 and LPDDR4X DRAMs are the most popular today, LPDDR5 DRAMs, offering a higher performance at a lower power than LPDDR4/4X, are expected to become available in 2020.

This whitepaper explains the various available LPDDR4/4X DRAMs and outlines the different possible system configurations with such DRAMs. Associated with the different LPDDR DRAMs and system configurations are the different number of loads on the Command/Address (C/A) and data (DQ) buses. The paper concludes with a Signal Integrity (SI) based analysis with results for different C/A and DQ bus loads at various data-rates. The same analysis can be applied to LPDDR5 DRAMs.

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