APMemory – IoT RAMs for the smart world

No problems with write-erase cycle limitations, cost effective and small “IoT-RAMs” is what AP Memory calls its multi-serial PSRAMs, which are characterized by their low power consumption and target the emerging markets around the IoT. This makes them suitable for use in portable and networked devices, from smartphones to tablets and wearables, GPS modules to embedded systems as well as in the emerging edge AI sector. “That’s why we call them “IoT-RAMs”, because if you need to network for setting up IoT environments, you can’t get past IoT-RAMs,” says Jun Gu, CEO of AP Memory. They are also suitable for deployment in harsh industrial environments.

But what is hiding behind the IoT RAM term? The main foothold of the company are the pseudo SRAMs (PSRAMs), i.e. RAMs that are internally structured like dynamic RAM (DRAM), but externally act like static RAM (SRAM). The major advantage: Unlike SRAMs whose cells consist of up to six transistors, PSRAMs operate internally with DRAM cells consisting of a single transistor plus integrated capacitor. The entire refresh logic for the DRAM cells runs internally, the user does not notice anything of it. He is dealing with conventional SRAM interfaces, so the pseudoSRAM behaves as the name suggests, as if it were an ordinary SRAM. However, because an SRAM cell usually consists of six transistors, a DRAM cell of only one plus capacitor, the PSRAM takes up considerably less chip area than a real SRAM despite the overhead due to the internal refresh logic and the interfaces. This makes them appropriately more cost-effective.

In addition, AP Memory has succeeded in significantly reducing standby current consumption through ingenious circuit technology. In addition to “Cellular RAM” PSRAMs with 16-bit parallel address/data multiplex ports in FBGA54 packages, Quad-SPI versions as well as Octal-SPI versions are now available as well. The benefit of QPSI versions: They require only 8 ports, which means they consume even less power than the Octal types, which are housed in ball grid packages with up to 24 ports. Both types hardly deviate from each other in package size.

But why do users use volatile memory at all? The reason is simple: Wherever data has to be constantly moved back and forth, i.e. the data content in the memory is constantly changing, flash memories reach their limits because their cells get worn out by constant overwriting. One example is active echo cancelling. The PSRAMs and LPDRAMs, on the other hand, do not know this kind of problem. That is why IoT-RAMs are now an integral part of corresponding memory multi-chip packages. Here again the careful circuit design of AP Memory makes a difference as these PSRAMs achieve a power consumption in standby mode that is five times lower than that of other manufacturers. In portable devices, this leads to a accordingly longer battery life.

In total, more than 80 AP Memory engineers are working to further develop the PSRAM technology and expand the product range. “In the meantime, we have advanced to number one among PSRAM manufacturers and our market share is around 80 percent,” says Jun Gu. With more than 160 employees, AP Memory has more resources than its competitors: “Above all, we can react very rapidly on new trends.”

The main trend: all around the IoT and Industry 4.0, new markets are emerging for memory with characterised by low power consumption. Particularly here, however, are the demands for more frequent rewriting. That’s why Gu prefers to describe the memories as IoT-RAMs rather than with their original, somewhat unwieldy name: “Especially the high demand that Edge devices create will give the market for IoT-RAMs a strong boost. For example, almost all narrowband IoT platforms now rely on IoT-RAMs, and there is a noticeable shift from embedded SRAMs to IoT-RAMs,” says Gu.

He also expects a lot from the fusion of artificial intelligence (AI) and the IoT into “AIoT”, which requires completely new memory architectures for which PSRAM technology is an excellent starting point. AP Memory is working at full speed on appropriate IoT RAMs. Sales of the new memory types are expected to increase noticeably this year already.

AP Memory’s portfolio ranges from Quad-SPI PSRAMs with memory densities of 16, 32 and 64 Mb and Octal PSRAMs (32, 64 and 128 Mb) to “Celluar RAM” PSRAMs with 32, 64, 128 and 256 Mb. Package options include SOP8, USON, BGA24/54, WLCSP and Known Good Die (KGD).

AP Memory is now working with a number of IC manufacturers to add IoT RAMs to their chipsets. These include, for example, STMicroelectronics, which uses the memory in the environment of its STM32 ARM Cortex MCUs. Whenever user requirements exceed the capability of on-chip-integrated SRAMs, the Quad and Octal PSRAM types from AP Memory with capacities ranging from 16 Mb to 256 MB step in.

Besides the IoT-RAMs, the DRAMs form the second main foothold of AP Memory. Here, too, the company relies primarily on Low-Power types, from which PSRAMs originated. Low-Power DRAMs (LPDRAMs) are used in all applications where smallest possible footprint on the printed circuit board is not the key, but rather high storage density. The number of LPDRAM I/Os is accordingly higher:

Compared to standard SDRAMs, up to twice as many.

The LPDRAM range of AP Memory includes LPDDR2, LPDDR3 and LPDDR 4 versions with memory densities of up to 4 Gb. Standard DRAMs include SDR SDRAMs (64, 128, 256 MB), DDR1 (64, 128, 256 Mb) and DDR2 (256, 512 Mb and 1 Gb) as well as DDR3 SDRAMs with 1, 2 and 4 Gb memory densities, all of which can also be supplied as KGD. Most of these DRAMs are available in various memory densities and organizations, including packaged versions. The same applies to automotive DRAMs in versions from 64 Mb to 2 Gb.

Jun Gu, AP Memory: “In the meantime, we have advanced to number 1 among the manufacturers of PSRAMs, our market share is approximately 80 percent. With over 160 employees, AP Memory has sufficient resources that enable us to respond very quickly on any new trends”.

In 2016 Micron founded the Xccela consortium, whose first members included Winbond, GigaDevice Semiconductor and AP Memory Technology. At that time it seemed highly desirable to standardize the multi-serial NOR flash interfaces. Until then, each manufacturer went its own way to develop cost-effective memories with multi-serial interfaces and the highest possible performance. Especially in applications where instant-on capability was important, developers were looking for memory ICs that could meet the increased demands. In the meantime, Elite Semiconductor Memory Technology (ESMT), Phytec, Elnec, Lyontek, NOR-MEM Electronics Co., ASR Microelectronics and Xenon Digital Workshop have joined the Xccela consortium, most recently STMicroelectronics joined by the end of last year.

Up to this date, AP Memory is the only member among memory IC manufacturers to contribute the volatile memory chips within the Xccela consortium. They are particularly suitable for use in speech recognition, sound reproduction and speech synthesis, for example. Generally for all applications in which new data has to be constantly acquired, computed, and old data overwritten Flash memories cannot reach the required number of write-erase cycles in the long run.

Conventional SRAMs would be too expensive, the use of LPDRAMs is sometimes possible, but often fails due to space constraints and the higher number of I/O ports. Whether IoT-RAMs or LPDRAMs are to be preferred depends on the respective constraints of the application. The Xccela bus is an open standard for communication between volatile and non-volatile memories and other chips such as MCUs, SoCs and A/D converters. The powerful Octal SPI bus uses 8 serial data lines and is compatible with the new JEDEC xSPI standard. It is configured for Single Data Rate (SDR) and Double Data Rate (DDR). The SDR version works with clock frequencies of 166 MHz, theDDR version with 200 MHz for data transfer rates up to 400 MByte/s. For the SDR mode 10 pins are required and 11 for the DDR mode.

For more info, contact an Ineltek office within your area or contact us at info@ineltek.com.

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