LPDDR flash claims edge on xSPI NOR in code execution

A new flash memory chip claims to offer real-time code execution for safety-critical applications serving domain and zonal controllers in semi-autonomous vehicles while exceeding the capability of today’s most advanced xSPI NOR flash devices. Domain and zone controllers, which consolidate many safety-critical functions, must process huge amounts of data in real-time; so more memory is needed to support growing code size and complexity.

Infineon Technologies also claims that its SEMPER X1 chip is the industry’s first LPDDR flash memory; the LPDDR4 interface offers the scalability and performance required for direct code execution from an external NVM device. It does that by facilitating a scalable interface in terms of bus widths and the number of channels.

Figure 1 SEMPER X1 is the world’s first LPDDR flash memory device enabling real-time code execution from external NOR flash. Source: Infineon

According to Sandeep Krishnegowda, VP of marketing and applications for flash solutions at Infineon, at advanced process nodes, automotive-qualified eNVM technologies are challenged by high cost and lack of scalability. “As a result, standard xSPI NOR flash does not meet real-time execute-in-place (XiP) performance requirements.”

Jim Handy, general director at Objective Analysis, provided a more detailed view of this issue. “What’s at issue is that NOR flash, which has served as the program storage for MCUs and ASICs since the 1980s, suddenly stopped scaling when CMOS logic processes started to use FinFETs at 14 nm,” he said. “The smallest process to support NOR is 28 nm.”

“Designers could either use a new memory technology like MRAM and ReRAM to replace the NOR, or they could use an external flash chip,” Handy added. The trouble is that the parallel and SPI interfaces for external NOR flash are orders of magnitude slower than embedded NOR.” To that end, some MCU designers have added an LPDDR interface, hoping that memory makers will offer products that can support their MCUs at a higher speed.

“SEMPER X1 is the first NOR flash I know to come with an LPDDR interface,” he said. “I expect to see similar offerings from Infineon and its competitors in coming years.” Handy is the co-author of an annual report on emerging memory technologies.

The embedded vs. external flash

When it comes to embedded flash and external flash settings, the traditional way is to execute from embedded flash. And external NOR flash can be used as a memory expansion. In what Krishnegowda calls a pivot point, design engineers can now execute from external LPDDR flash with a high-performance LPDDR interface enabling real-time code execution from external flash.

“The real-time processors in domain and zone controllers need the performance of advanced process nodes,” he added. “So, real-time processors without embedded flash need equivalent performance from an external flash.”

Figure 2 SEMPER NOR flash is targeted at automotive, industrial, datacenter, and communications applications where failure is not an option. Source: Infineon

“SEMPER X1 offers significant performance gains compared to standard xSPI NOR flash as well as standard LPDDR4 DRAM,” Krishnegowda said. With an LPDDR4 interface, it operates at 3.2 GBytes/sec throughput and features a multi-bank architecture to meet the performance and density requirements of domain and zone controllers.

Krishnegowda added that SEMPER X1 flash has been architected and designed for functional safety. It’s ISO 26262 ASIL-B compliant and offers advanced error correction and other safety features. Moreover, it supports over-the-air (OTA) firmware updates with zero downtime.

At a time when software-defined vehicles increasingly demand real-time code execution for safety-critical applications like engine control, a new memory device taking advantage of the LPDDR4 interface can bring value to the next-generation automotive domain and zone controllers running safety-critical, real-time applications. Especially, when it claims to deliver 8 times the performance of current NOR flash memories and achieve 20 times faster random read transactions for real-time applications.

SEMPER X1 is sampling now with commercial availability in 2024.

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