Clock Drivers Can Handle the Heat

Article By : Gary Hilson

Both automotive and edge applications are defined by harsh operating conditions, driving the need for robust signal integrity.

A key characteristic of automotive memory is that it must be able to withstand extreme temperatures, but edge computing is also adopting some of the same technologies to handle harsh conditions.

Renesas Electronics’ first industrial temperature DDR5 and DDR4 registered clock drivers (RCDs) can handle temperatures as low as -40 degrees Celsius and as high as 105 degrees Celsius, which make them appropriate for memory devices going into vehicles, whether it’s to handle the heat generated by the engine or being parked during the winter months.An RCD sits between the memory controller and DRAM ICS, redistributing the commands and address signals within a memory module to basically to improve the signal integrity and connect more memory devices to one DRAM channel. Given the amount of memory content supporting the intelligence in today’s vehicles, whether autonomous or not, any RCD is going to have to be able to handle the extreme environment of a car with high reliability. Most industrial temperature RCDs only operate in the 0 degrees Celsius to 70 degrees Celsius range, said Allen Youssefi, principal engineer for memory interface product management at Renesas.

Other applications besides automotive are just as likely to make use of Renesas’ new RCDs, he said in an interview. The company’s new RCDs are also targeted at Industry 4.0, 5G, and edge applications. The latter combine traditional compute and communications architectures together, which demand server components that can withstand the harsh environments at the network edge, which is why the company has put a lot of effort into qualifying its RCD products over extended temperature ranges for emerging use cases.

There’s a lot of data in in edge applications, especially those doing artificial intelligence inference or machine learning, whether they use 4G or 5G. “There has to be a back-end infrastructure to support all that data movement,” said Youssefi. “When you look at those inside of those infrastructures, you will see a bunch of servers there that need DRAM memory modules.”  All these applications are hungry for memory bandwidth. “If you don’t have a registered clock driver that takes the load away from the DRAM itself on the module, you’re going to run into signal integrity issues and power issues.” Higher data rates require an RCD for buffering, he said. “There’s a lot of signal traffic.”

The RCD component for an automotive application goes into a mini server that sends and receives a lot of data. “Even though it’s a small server in that car or the autonomous vehicle, it’s pretty important.” He said these automotive mini servers collecting data are not unlike those sitting at the edge.

Allen Youssefi

Reliability is especially important in automotive as well, and regardless of temperature requirements, Youssefi said its DDR4 and DDR5, which are in production now, have gone through a great deal of testing validation, and even revisions before they made it into production. “They’ve been and qualified and validated with all of our customers that are using these products, as well as ecosystem enablers.” He said as more customers working in emerging applications are requiring RCDs that can specifically handle lower and higher temperatures, Renesas has implemented improved design techniques and different internal methods to screen the RCDs the higher temperature range.

DDR DRAM, including the lower power flavor, is likely to see uptake at the edge as more powerful computing is required in harsher environments, as well as automotive applications.

The latest update to the LPDDR5 standard released by the JEDEC Solid State Technology Association, improves performance, power, and flexibility, but also includes signal integrity improvements with TX/RX equalization that make it more reliable; an Adaptive Refresh Management feature helps the memory device adjust in more stressful operating environments, including more extreme temperatures.

This article was originally published on EE Times.

Gary Hilson is a general contributing editor with a focus on memory and flash technologies for EE Times.


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