Tensilica and Design IP Blogs

With highly effective DDR4 and LPDDR4 class memories, it’s not always easy to know what kind of memory will best fit the needs of your application? What is the optimal compromise between keeping costs in check and optimizing performance?

To answer that we have to take a step back and look at the history of the DDRs. In the PC memory area, we have the DDR2, DDR3 and DDR4. On the LPDDR front there are LPDDR2, LPDDR3, LPDDR4.

Figure 1: History of DDR Memory

The DDR4 standard took from 7 to 10 years and it’s now specified up to 3200 Mbps. LPDDR4 on the other hand is specified up to 3200 Mbps as of today and has a goal to reach 4266 Mbps data rate pretty soon. From the perspective of available samples, you can get 2133 or 2400 Mbps today. LPDDR4 3200 Mbps memory samples should be coming at the end of this year.

The fact that LPDD4 memory has caught up with PC memory data rates, and will actually surpassed it at 4266 Mbps has opened up new possibilities for certain applications like the automotive industry infotainment systems or high-end security camera applications. There are many other applications seeking higher bandwidth without necessarily an increase in memory capacity. Because of that, in order to fulfill the bandwidth requirements, you would have to use multiple DDR4s. Or you can utilize one or two LPDDR4 memory devices.

That leaves us with an interesting situation: while the single memory cost for LPDDR4 may be higher, the total memory subsystem memory cost using LPDDR4 can be lowered, because you can stay with lesser components that keep the overall cost in check as well. 

Introducing LPDDR4 in applications that traditionally did not use the LP features can now achieve much higher bandwidth (meaning higher performance) as well as keep cost in check while maintaining memory capacity needs that you have. This is a new trend we’re seeing in the industry where certain applications can use the LPDDR4 class memory instead of the DDR4 for their needs.