Memory & Storage Technology
USB Flash Drives: Components, Uses, and Myths Dispelled
By Paul Pickering for Mouser Electronics
The USB flash drive—also known as a jump drive, data stick, or thumb drive—continues to be the most popular portable storage device, with sales estimated to exceed 500 million annually by 2020. Although cloud storage is making headway in the same market spaces, USB drives offer capacity, speed, and size that make them ideal for many uses beyond just storage, including some perhaps unexpected uses as well. This article explores what’s inside a USB flash drive, explores various uses, and dispels common myths.
A Look Inside
A typical USB flash drive includes a USB connector, a mass storage controller, one or more flash memory chips, and a crystal oscillator, as well as additional features such as jumpers, LEDs, switches, and unpopulated space (Figure 1):
Figure 1: The internal components of a typical USB Flash Drive.
- USB Standard-A, "male" connector, which interfaces with the host computer
- USB mass storage controller, which is a microcontroller with on-chip ROM and RAM
- Test point, used for loading code into the microcontroller
- Flash memory chip, used to store data
- Crystal oscillator, which produces the clock signal and controls data output
- LED, which indicates active data transfer
- Write-protect switch, used to enable and disable writing of data
- Unpopulated space, potentially used for second flash memory chip
The memory capacity and speed of USB drives continue to increase. As of the time of this writing, 512GB USB drives are becoming common, with 1TB capacity also available. The average speed for a highly-ranked 64GB USB 3.0 device is 104MB/s for a write operation and 171MB/s for a read operation.
Recently, USB drives incorporated the Type-C connector, which provides a yet even smaller and thinner connector compared to the Type-A connector. The Type-C connector has a rounded, symmetric shape that fits into ports easily yet securely, and works either way up (solving the problem that everyone has faced where they have to stick a USB plug in three times before it eventually goes in). Figure 2 shows a USB drive that accommodates both the old and the new sockets.
Figure 2: A combination USB Type-C/USB 3.0 drive (Source: SanDisk)
USB Drive Uses
Although the USB drive was designed as a storage solution, users are finding new purposes for its small size, capacity, and portability. For example, USB drives are making applications portable and accessible for average consumers. When you’re away from the office, for example, you can take a USB drive containing all of your software and personal data; then, when you plug it into another computer, you have access to all of your information. When you unplug the drive, none of your personal data is left behind.
USB also makes it simple to install and update software. PortableApps.com, for example, offers lightweight versions of over 300 applications including office suites, browsers, image editors, and games. One caveat is that running portable applications does tend to increase the number of write cycles, which may reduce the drive’s operating life.
High-End Applications
There are multiple grades of USB drives for different applications. For example, Swissbit provides storage for applications where performance and reliability are key, such as in communications and networking, industrial, embedded, military and aerospace, transportation, casino gaming, and medical equipment markets. The company’s unitedCONTRAST II USB 2.0 flash drives use a high-end, USB 2.0 flash memory controller for high data reliability and endurance. They contain an error-correcting engine based around the cyclic Bose-Chaudhure-Hocquenghem (BCH) code engine (named after its inventors) that can correct up to eight random bit errors per sector. Figure 3 shows the internal block diagram of this drive.
Figure 3: System block diagram of a high-end error-correcting USB drive (Source: Swissbit)
For secure applications, USB drives are available that incorporate 256-bit Advanced Encryption Standard (AES) encryption of all data; some even include a mini keypad for password entry. Secure USB drives require a specialized Flash Memory Controller (FMC) such as Microchip’s SEC2410. This device is based around a 32-bit ARM Cortex M3 microcontroller; it includes a USB 2.0 interface and a hardware AES encryption engine.
Industrial Espionage
Although most computers become infected via email attachments, software downloads, or social media, a USB drive can be an efficient way of spreading a virus, worm, or other malware, especially if the computer doesn’t have online access. For example, a USB drive is thought to be the means by which an unnamed cyber-attacker infected Iran’s nuclear program with the infamous Stuxnet virus. Stuxnet targeted only Siemens Step7 Programmable Logic Controller (PLC) software, used by Iran for its uranium-enrichment centrifuges. What’s more, USB-borne malware can spread both ways: Inserting a clean USB stick into an infected machine can unwittingly help propagate the infection.
Computer Forensics (COFEX)
Inserting unwanted programs via USB isn’t just confined to evildoers (known as “black-hat” hackers). The “white-hat” types can use computer forensics to gather and preserve evidence from a computer for later use in a court of law. Often, the investigator gains access to the target machine via a USB drive. For example, Microsoft offers a tool for forensic investigators called Computer Online Forensic Evidence Extractor (COFEE). It helps extract information such as passwords and collect data on a Windows machine and is hosted on a USB flash drive. Other suppliers offer similar programs.
Security Keys
In an era of massive and well-publicized data breaches, security of both personal and professional data is a constant concern. Both commercial and open-source sites offer software that turns a USB drive into a security key. A utility running on the computer constantly checks for the presence of an encrypted key stored on the USB drive. When the USB drive is plugged in, the computer operates normally. Once you remove the drive, your computer is automatically locked and requires a password for access.
Some programs go even further: One program takes a picture any time an unauthorized user tries to access your computer when you’re away; the program will also sound an alarm if someone enters an incorrect password.
Brand Promotion
Product designers can use a USB flash drive as a blank canvas for their creativity. Figure 4 illustrates a USB flash drives used to promote the Mouser brand.
Figure 4: The compact size and shape of a USB drive offers creative opportunities. (Source: Mouser)
USB Myths Dispelled
Since USB flash drives were first introduced, myths and legends have grown around them. Here are a few of the most popular:
Myth: Magnets can damage or erase USB Drives.
Fact: USB drives are not built from magnetic materials, so they’re impervious to magnetic fields. The information on cassette tapes (remember them?) and credit cards, on the other hand, can be impacted.
Myth: Water Ruins USB Drives.
Fact: The water itself doesn’t harm the drive; the damage occurs when you power on the device and current flows through water droplets to places it is not intended to go. Make sure to dry out your device thoroughly before you plug it in. If you really must put your USB through the Heavy-Duty Wash cycle and use it right afterwards, the Kingston Digital 64GB USB 3.0 DataTraveler drive is for you. It’s designed for operation in rugged environments, has a shock-resistant rubber casing, and can withstand immersion in one meter of water for up to an hour.
Myth: Removing a USB during operation can damage it.
Fact: The USB drive will be fine. USB ports are designed to be hot-pluggable, but there is still a slight risk from ElectroStatic Discharge (ESD). The risk is miniscule, but present, so manufacturers include this detail in datasheets and similar.
Conclusion
The USB flash drive offers capacity, speed, and size that made them ideal for multiple uses, ranging from making applications portable to industrial espionage to brand promotion. The USB drive itself contains a number of components and features, and manufacturers continue to enhance the drive’s capabilities to meet consumer demands. Although cloud storage solutions now compete in some of the same markets, USB flash drives will continue to be a solid solution with multiple uses.
As a freelance technical writer, Paul Pickering has written on a wide range of topics including: semiconductor components & technology, passives, packaging, power electronic systems, automotive electronics, IoT, embedded software, EMC, and alternative energy. Paul has over 35 years of engineering and marketing experience in the electronics industry, including time spent in automotive electronics, precision analog, power semiconductors, embedded systems, logic devices, flight simulation and robotics. He has hands-on experience in both digital and analog circuit design, embedded software, and Web technologies. Originally from the North-East of England, he has lived and worked in Europe, the US, and Japan. He has a B.Sc. (Hons) in Physics & Electronics from Royal Holloway College, University of London, and has done graduate work at Tulsa University.
