If there is one enduring trend for memory design in 2014 that will carry through to next year, it’s the continued demand for higher performance.

“The trend toward high performance is never going away, and research and engineering will always be focused on trying to keep up,” Lou Ternullo, product marketing director of memory and storage IP at Cadence, tells us. At the same time, the goal is to keep costs down, especially when it comes to consumer applications using DDR4 and mobile devices using LPDDR4. “Consumer applications are particularly sensitive to cost,” he says.

Ternullo believes LPDDR4 will gain a strong foothold in 2015, and not just to address mobile computing demands. Other applications that require lower cost, lower power consumption, and higher performance will benefit from LPDDR4, such as HDTVs, cameras, and other display devices -- and designers will need to adapt to the demand.

But while Ternullo is bullish on LPDDR4, the reality is that LPDRR3, or even DDR3 for that matter, will be around for the foreseeable future. He notes that customers want to hedge their bets with entire subsystems that will use the lowest-cost DRAM, whatever that may be, so they are looking for subsystems that can easily accommodate DDR3 in the immediate future, but will also be able to support DDR4 when it becomes cost-effective or makes more sense.

Cadence will be exhibiting at DesignCon in January, but it recently hosted its own Front-End Design Summit, which addressed another trend: With the adoption of advanced process nodes, design complexity is expanding much more rapidly than the design teams themselves, so it’s becoming pretty much mandatory to solve the most challenging design problems at the earliest RTL and pre-RTL stages of the development process. Designers now need to analyze and consider metrics that typically would have been first measured during implementation.

Keysight (formerly known as Agilent) will be showcasing its DDR Memory solutions at DesignCon. It will also be delivering papers covering design, simulation, and measurement challenges and solutions associated with DDR4 and LPDDR4, including a session on the latest test-and-measurement techniques to address the challenges raised by increased system data rates beyond 2,400 Mbit/s and how to minimize design risk. Keysight will also be presenting on ways to overcome simulation, probing, and test challenges raised by JEDEC’s BER contour spec for DDR4.

Another key trend for 2014 that will continue into 2015 is constraint-based design, says Bob Potock, VP of marketing at Zuken, because standards are so tight, as are timelines. On the manufacturing floor, failures are likely when changing memory vendors; constraint design anticipates this and can minimize those failures, he says. Meanwhile, SoC vendors are providing calibration tools for controllers, so when memory is switched out, it can be accommodated.

“Manufacturing floors are getting more challenging as well, because if you have an onboard memory failure, generally you can’t get to the OS, and you may have a board failure that you can’t debug,” says Potock, “because in-circuit testing on these small geometries is becoming very challenging.” Design, calibration, and diagnosing problems are strongly intertwined, he tells us.

DDR memory has a few parameters that can be addressed with constraint-based design, such as maximum length in terms of arrival times being consistent across a set of signals, whether it’s the data bus or the address bus, for example. “Those are probably the most critical ones,” says Potock. But because the DDR memory parameters are so tight, you can only do an optimal set of constraints, he notes, and then there are variations in board fabrication and chips, depending on the vendor, and that's when calibration comes into play.

Potock says memory is becoming a one of the most important concerns for designers when going to high-volume fabrication, as well as keeping up with emerging memory technologies when it’s unclear which ones may flourish. He says Zuken works closely with customers to understand what their future plans are for technologies as well as how the standards for a particular memory are maturing.

Like other vendors offering design tools, Zuken will be at DesignCon 2015 next month showcasing its CR-8000 Advanced PCB Design Software.

By: DocMemory
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