Although emerging non-volatile memories have been touted as options for the Internet of Things, in the short term, flash looks to be the go-to memory for smart homes devices, with a focus on reducing power consumption.
Adesto Technologies, known for its CBRAM for niche applications requiring radiation tolerance, just announced its DataFlash-L series line of memory products for smart home applications that emphasize low power operation and higher system efficiency. In a telephone interview with EE Times, Paul Hill, Adesto's director of marketing, said the DataFlash-L family maximizes battery life and minimizes the need for on-board capacitors by using less power during active modes and offers designers the ability to operate the system in lower voltages.
Adesto's DataFlash-L (AT25PE) series offers a range of power-saving features including wide operating voltage range of 1.65V to 3.6V and “ultra-deep power down" mode. Hill said this enables home control systems and other wireless devices to operate from unregulated battery supplies and may not require low drop out or boost regulators to manage the power supply rail during a power-failure. The device's sleep mode means it can function with a standby current of less than 400 nanoamps, he added, an important feature for battery-operated devices. “They spend a lot of time in deep sleep," he said.
Hill said many IoT devices are moving to OTA connectivity—a security system connected to an Amazon Echo, for example—and operate in real-time when they're not in sleep mode. Adesto's DataFlash-L includes a page erase feature and built-in intelligence to automatically manage internal programming and erase tasks, reducing CPU overhead by offloading memory management tasks and thereby increasing efficiency.
While Hill does anticipate that other emerging technologies will find their way into IoT and smart home applications in particular, he said flash is well-established and customers don't see the need for anything else.
Adesto is currently seeing smart home products with sockets and designs that operate at 1.6v-3.6V, so any product that runs at lower voltage will require a new design or redesign to incorporate a new memory device. It does manufacture memory products that specify a 1.2V power supply, such as its Moneta RM3313 product family, but it has yet to be adopted into any smart home applications.
Winbond Electronics Corp., meanwhile, is heading down to that 1.2v range with its recently expanded flash product portfolio. The company introduced its lowest-voltage SpiFlash memories to date at 1.2 and 1.5V, which it said are the industry's lowest NOR flash voltages. Krishna Shekar, Winbond's senior director of flash marketing, told EE Times via telephone the company's SpiStack technology enables it stack NOR on NOR, NAND on NAND and NOR on NAND. “That gives us a lot flexibility," Shekar said.
The new SpiFlash family comes in 8-pin packages to give designers serial flash memories for audio, wearable, IoT and other applications requiring low power in small packages. The 1.2V products cover an operating voltage range from 1.14V to 1.3V for very- low-power designs, while the 1.5V devices have a wider operating voltage range from 1.14V through 1.6V to portable designs the advantage of sustained battery operation, both when the battery is fresh and when its voltage decreases from use and/or time.
The lower voltage devices are a long time coming, added Conrado Canio, technical marketing manager for Winbond's flash products, as the 1.8V products were first introduced a decade ago. He said the company's new SpiFlash line is perfectly matched for the low power devices with 1.5V battery cell. “There are already chipsets that can operate in this range," Canio said.
Like Adesto's new offerings, the Winbond product update bears in mind that many smart home devices are spending a lot of time in sleep mode, but need to power up quickly to handle data transmission. SpiFlash is also designed so IoT devices in the home require fewer batteries—only one AA or AAA, rather than two, said Canio. They also contribute to PCB space savings, he added, as smaller low-dropout regulators can be used due to the design's lower voltages, saving PCB area and bill-of-materials costs. The lower voltages also reduce noise coupling, which provides for more-compact PCB designs.
Winbond also sees flash continuing to dominate IoT for the foreseeable future given its data retention and endurance characteristics, said Canio. "It's proven over time," he said.
Other memory technologies that are seen as contenders for IoT applications include Adesto's CBRAM, as well as other resistive RAM such as Nantero's , while the improved economies of embedded MRAM manufacturing suggests it has potential as well.
Alan Niebel, president of WebFeet Research, said Winbond's 1.2V serial quad NOR should use significantly less power than competing higher-voltage NOR components, and makes it ideal for smart home applications that use energy harvesting or a long-term battery since on extending device life and reducing the amount energy needed for data transmission. “With the lower voltage, you still have enough speed running at 80 megahertz," he said. “The lower voltage of the system reduce the number of batteries you have to have."
Niebel said it's also important not only to have a system that go into sleep mode when not active, but also come back at a “good clip." He said Winbond has been working at this for quite a while and first to market. There are other potential alternatives to flash, such as embedded MRAM, as well as Adesto's CBRAM, he said. “That also runs at very low power but they don't have the densities," Niebel said.
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