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LPDDR4: What Makes It Faster and Reduces Power Consumption

DRAM memories are the ‘heart’ of any computational device, e.g. smart phones, laptops, servers etc. LPDDR4 was mainly designed to increase memory speed and efficiency for mobile computing devices such as smartphones, tablets, and ultra-thin notebooks.  It supports speeds up to 4267Mbps (double the speed of LPDDR3) and 1.1 V input/output buffer power, along with many other improvements compared to its predecessor (LPDDR3/LPDDR2). Below is a comparison of key features between all the three generations of LPDDR.

lpddr-comparison

Dual Channel Architecture

The memory architecture of LPDDR4 has been modified to achieve higher bandwidth and lower power consumption, a primary requirement of current generation computing devices. It has reduced power consumption by lowering the supply voltage, while increasing the bandwidth.

The architecture of LPDRR4 memory supports dual channel, while LPDDR3/LPDDR2 only supported single channel devices. In single channel, data signals need to travel a longer distance between memory array to I/O pads, hence consuming more power to transmit data.  Dual channel helps by providing a shorter Data Path which leads to reduced delay and power consumption to provide output data thus achieving higher bandwidth with low power consumption. Command Address (CA) pins are also reduced from 10 to 6, which contains command, address, and bank information. The dual channel architecture can accommodate 32 data bits (16×2), with 16 data bits per channel.

lpddr-channel-architecture

LPDDR4 provides flexibility in rapid switching with its ability to switch frequency points. It contains two Frequency Set Points (FSPs) in-order-to first store the operating frequency related information in FSPs (duplicate of all DRAM registers) and then switch between the stored operating frequency with single mode register write change. This translates to a significant reduction in latency for switching operating frequency and hence low power consumption.

LPDDR4X

Apart from LPDDR4, a variant called LPDDR4X is also available in the market. This variant is designed to reduce power consumption further, especially in smartphones. It is identical to LPDDR4, except that it consumes even less power (LPDDR4X: 0.6 Volt Vs LPDDR4: 1.1 Volt).

LPDDR4 Packaging

LPDDR4 supports three different combinations of packaging:

  1. Standard Package: Contains only LPDDR4 die having standard (32x) dual channel.
  2. Byte-Mode Package: Contains only Byte-mode LPDDR4 die having its DQ connected to either lower byte (DQ [7:0]) or to upper byte (DQ [15:8]).
  3. Mixed Mode Package: Contains both standard and byte mode LPDDR4 die, having some ranks containing only standard die and some containing only byte-mode die.

lpddr-package-config

Future of LPDDR

Ever since JEDEC released LPDDR4 specification in 2014, It has been the first choice of mobile companies. The advancement in communication technology demands higher and more powerful processing along with faster and compact memory devices. Currently LPDDR4 can meet industry demands, but with emerging technologies like self-driving cars, IoT and wearables, and the next wave of smartphones and tablets, more firepower in memory is required.

The future is closer than we think!

Stay tuned for our upcoming blogs on DRAM and Flash memories. For more information on Synopsys memory VIP, please visit: www.synopsys.com/vip.

Authored by Amit Paunikar