Feature: Thermal management


Reliability and more Reliability concerns have led automotive manufacturers to abandon traditional hard disk drive (HDD) storage devices, which have limited lifetime and are prone to mechanical failure. Instead, designers today prefer to use mass storage devices based on NAND Flash memory, such as solid state disks (SSDs), eMMC drives or universal flash storage (UFS) devices. NAND Flash has become the preferred technology for mass storage


NAND Flash- based storage devices for high reliability in automotive applications


By Silicon Motion design engineers W


ith every new generation of vehicle, the automation, safety and navigation systems become more sophisticated. Supported by an array of cameras, radar (RF) and LiDAR (optical) ranging systems, sensors and more, advanced driver assistance


systems (ADAS) generate and process huge volumes of digital data. Infotainment systems, too, are growing in code size, as drivers demand reliable and accurate navigation and information and passengers look for more entertainment options in the front and rear of the cabin. In functional terms, the car is becoming a data centre on wheels, which requires high-speed access to a large amount of data, in real time.


30 November 2022 www.electronicsworld.co.uk


in mobile phones, laptop computers and other consumer devices, as well as in SSDs, because it offers a valuable combination of high memory density and high performance. Tis means that huge data storage capacity can be provided in a small device, and the user benefits from rapid access to stored data. Tese characteristics are very important to automotive manufacturers. But automotive applications impose special requirements that raise important additional questions about the choice of NAND storage device: • Performance – in applications like driver assistance and navigation, latency is a key figure of merit. Automotive manufacturers require fast read and write speeds and high data throughput.


• Data integrity – every read and write operation carries a risk of generating bit errors, which can lead to data loss or corruption. Reliability is a critical factor in the automotive market and, in a storage device, data integrity is an important marker of reliability.


• Data retention – unlike a consumer device such as a mobile phone, a vehicle is expected to have an operating lifetime of at least ten years. Automotive manufacturers want to be confident that their chosen NAND storage device will retain data for the life of the vehicle.


Zero defects In vehicles, long-term reliability and lifetime of an electronics component such as a mass storage device are crucial criteria. Te automotive industry applies strict qualification tests, according to the AEC-Q100 standard, to the integrated circuits used in automotive electronic control units (ECUs), with the aim of achieving zero defects over a long lifetime, at temperatures of 85°C or higher. Te goal of reducing the component defect rate to zero is important


because of the long lifetime of a vehicle, the high number of components it carries, and the huge cost of rectifying a known fault in a fleet of vehicles in service – not to mention the reputational damage to a car maker’s brand. To illustrate the point simply, imagine a single ECU consisting of


1,000 parts. If the ECU manufacturer tolerated a defect rate as low as 1ppm, this single ECU alone would be responsible for 1,000 faults in a fleet of a million vehicles. And according to a 2019 report from analyst firm IHS Markit, a new luxury vehicle can contain as many as 150 ECUs. Tis is why the automotive industry imposes the goal of zero-defect


rate, and its strategy for reaching that goal is to apply a component- qualification process, codified in the various AEC-Q10x standards. Te criteria for AEC-Q100 qualification, for example, are extremely strict and verify a component’s reliability across a number of test parameters. Te main reliability tests are:


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