With two flash dies in a single package, SpiStack has been designed to provide fast, reliable and risk-free OTA updates which are now becoming a critical feature in automotive, internet of Things (IoT) and industrial applications.
“OTA enables designers to deliver firmware updates over the air to ensure security and reliability of devices, and also offers a way to deliver new features and functionalities.” said Jooweon (JW) Park, VP of Code Storage Flash Memory at Winbond. “However, in order for this technology to be widely adopted, it needs to be 100 percent successful and done quickly so that it does not cause any disruption to the user. This is where SpiStack has a unique advantage with its two stacked dies in a single device.”
OTA firmware updates for automotive electronic control units (ECU) need to be conducted in a safe environment, without having to consider wireless communication stability. Typically, there is an OTA Manager role for car gateways that control the OTA task for related ECUs. The Manager handles the update process for all ECUs within the vehicle, controls the distribution of firmware updates to ECUs, and tells the ECUs when to perform the update.
The OTA Manager needs to provide fast programming to restore the updated firmware under a stable communication environment, and store the new firmware while the ECU waits to be updated with new firmware..
Winbond’s SpiStack series enables stacking of multiple devices with the SPI interface. The stack can be homogeneous by stacking two or more SPI NOR flash or by stacking two or more serial NAND devices. The SpiStack can also be stacked with heterogeneous flash types such as putting an SPI NOR flash on top of a Serial NAND.
SpiStack provides designers with faster OTA updates. For example, an embedded system that uses a single-die 256Mbit NOR Flash device for code storage housed in an 8mm x 6mm WSON package can be replaced by a 512Mbit SpiStack device in the same package with two 256Mbit NOR Flash dies stacked one on top of another.
The two-die device can support Read While Write operation for OTA updating without suspension of read operations and with no risk of losing the existing firmware image in the event of an unexpected power interruption.
SpiStack also ensures greater density in a small package with fewer pins and a similar layout, resulting in reduced board size. Booting time shares the same performance with SPI NOR and SpiStack, which means NAND+NOR in a single package.
The NOR flash can fully cover the initial latency of Serial NAND, thus achieving fast booting throughput the same as NOR flash, which can save 90% programming time compared to NOR flash only.