USB Flash Drive

Written on March, 28, 2025

Contents

• Definition
• Functions
• Overview
• Components
  • USB Plug (aka USB connector)
  • NAND Flash Memory Chip
  • Mass Storage Controller Chip
  • Crystal Oscillator
  • Printed Circuit Board (PCB)
  • Case
  • Optional Components
• Transfer Speed
• Lifetime and Wear
• Security and Encryption
• Explanation
• Cost
• Conclusion
• References

Definition 

A USB flash drive (aka USB stick, memory stick, thumb drive, or pen drive) is a small, portable device that is used to store and transfer data between machines. It is designed to be compatible with any device (desktop, PC, projector, 3D-printer, etc.) that has a USB port in a “plug and play” fashion i.e., it functions without any explicit configuration from the user. Each USB flash drive varies in physical appearance, storage capacity, transfer speed, lifetime, security, and cost. 

Functions 

A USB flash drive primarily functions as a portable storage device capable of persisting any form of digital data—such as documents, images, videos, software, and even entire operating systems (OSs). Storage capacity varies widely across USB flash drives, typically ranging from 2-64 GB, with some designed to hold up to 4 TB of data. While they can theoretically store any type of data, specific USB flash drives are limited by their storage capacity and formatting. The format of a USB flash drive is the file system it uses to organize its data. Corollary functions of USB flash drives include: 

• Quick data transfer between devices: e.g., porting a 3D model to a 3D printer, copying a presentation to a projector 
• Media sharing: e.g., sharing large video files with a friend 
• Portable backup: e.g., saving important documents from a PC to protect against data loss if the computer gets damaged 
• Boot medium: e.g., booting into an Ubuntu system stored on a bootable USB flash drive from a Windows computer 

Overview 

A prototypical USB flash drive is rectangular and weighs around 1.10 oz (30 g). The main materials used are plastic for the outer cover, metal for the USB plug, and silicon for the internal flash memory and controller.  

USB flash drives are often described as thumb sized. Exact dimensions vary across manufacturers and styles. A prototypical uncased USB flash drive measures approximately 1.75 x 0.52 x 0.18 in (44.4 x 13.1 x 4.5 mm). Since case styles vary, the dimensions of a prototypical encased USB flash drive ranges. However, a typical one would measure around 2.25 x 0.75 x 0.4 in; consider the USB flash drive depicted in Figure 3. 

There are no limits on USB flash drive appearance as long as the device contains the essential components that allow it to function. Because of this, USB flash drives can be made from unconventional materials like wood or completely custom designed. 

Components 

USB Plug (aka USB connector) 

A metal piece that plugs into USB ports on another device (Figure 6: 1). Because of its shape it is also referred to as a male plug. To ensure reliable connectivity, USB plugs are made from durable materials such as stainless steel. There are two USB plug types: USB-A and USB-C. USB-A plugs are wider, rectangular, and unidirectional, meaning the orientation they are plugged into a device matters, i.e., it may require flipping to be in the proper orientation. USB-C plugs are smaller, slightly rounded, and reversible. While USB-A is still used, it is a legacy standard and is gradually being replaced by the faster, more versatile USB-C.  

NAND Flash Memory Chip 

Where a USB flash drive’s data is stored (Figure 6: 4). Flash memory is a type of electronically erasable programmable read-only (EEPROM) non-volatile storage, which means that it supports erase, write, and read operations and retains its data without power. This type of memory was designed to perform erasures quickly or “in a flash,” which is how it earned its name (Bigelow, 2023).  

At the lowest level, memory is a specially designed electronic circuit. NAND flash memory is differentiated from other types of flash memory by its circuit design, which is similar to that of the logical NOT AND (aka NAND) gate. Because of its design, NAND flash memory is slower at reading data than other types of flash memory. It also wears out faster, which means it has a shorter lifetime. However, it is capable of storing more information in less space and writes/erases faster with less power (But what is NAND, n.d.). 

Mass Storage Controller Chip 

A microcontroller (a small, specialized computer), which runs software that determines how data storage, reading, and writing operations are performed (Figure 6: 2). It manages data transfer between the device a USB flash drive is plugged into and the drive’s flash memory.  

Crystal Oscillator 

Provides the rhythm or “clock” to which data transfer operations are performed (Figure 6: 5). It ensures stable and accurate digital information transfer between a device and USB flash drive. 

Printed Circuit Board (PCB) 

Connects the USB plug, controller chip, and flash memory chips together allowing data in the form of electrical signals to pass through the USB flash drive. The PCB is typically green but can be other colors. The one in Figure 6 is red. 

Case 

A plastic or metal enclosure. It protects all the internal components of a USB flash drive from damage, dust, and moisture.  

Optional Components 

• LED Indicator: an LED light that shows when a USB flash drive is in use (Figure 6: 6).  
• Write-protect switch: a control that prevents write access to the NAND flash memory chip (Figure 6: 7). 
• Attachment point: a hole in the case that can hold a ring for attaching a USB flash drive to a keychain. 
• Extra space: a location that can hold more NAND flash memory to increase a USB flash drive’s storage capacity (Figure 6: 8). 
• Plug cover: a plastic, wooden, or custom designed piece that fits over the USB plug to protect it. 

Transfer Speed 

Different USB flash drives have different speeds. USB flash drives that use USB 2.0 have transfer speeds of up to 480 Mbps while the newer USB 3.0 supports a max speed of 5 Gbps (Johnston, 2024). USB 3.0 is more than 10 times faster than USB 2.0. For example, transferring a 16 GB video file from a computer to a USB 2.0 flash drive would take 5 minutes compared to 28 seconds for a USB 3.0 flash drive (Johnston, 2024). There are newer versions of USB such as USB 3.1, USB 3.2, and USB4 that have even faster transfer rates. 

Lifetime and Wear 

A USB flash drive has a finite lifetime. A high-quality USB flash drive should be able to store data accurately for ten or more years (Stiemer, 2025). Because data is stored using electrons in a circuit, data integrity is tied to the electron’s behavior. Factors such as long-term exposure to high temperatures or decades-long storage can lead electrons to “leak” from their memory locations, resulting in data degradation or loss (Stiemer, 2025).  

The ability of a USB flash drive to retain its data with integrity is also affected by the number of program/erase (P/E) cycles it supports. A P/E cycle refers to the process of writing data to a memory location of the drive, then clearing the same area to prepare it for new data. A high volume of P/E cycles exhausts a critical physical resource (the oxide layer) of NAND flash memory, leading to reduced storage integrity or failure (Bigelow, 2023). This phenomenon is called wear. Importantly, USB flash drive reads do not contribute to wear. A basic USB flash drive supports 100,000 P/E cycles before wearing out, while some last for 1 million or more cycles (Bigelow, 2023).  

Summarily, the lifetime of a USB flash drive is determined by environment factors and P/E cycle count. Over extended periods, data will inevitably degrade as electrons leak. Consequently, USB sticks are not ideal for long-term storage. 

Security and Encryption 

There are two main options for securely storing sensitive data on a USB flash drive. The first option requires buying an encrypted USB flash drive. These come with built-in encryption hardware and some even boast integrated pin pads (Kingston Technology, 2019). The second option entails using encryption software on a computer to secure the data on a USB flash. Subsequently plugging the USB flash drive into a device would require entering a password before being able to access and modify the data. 

Hardware encryption is stronger and faster, but more expensive. Software encryption is more flexible and can be used with USB flash drives that do not have built-in hardware encryption capabilities. 

Explanation 

The components of a USB flash drive work together to enable data transfer and storage from a device to the drive and from the drive to a device. To transfer data to a USB flash drive or view and modify existing data on it: 

1. Plug a USB flash drive into a device by fitting its USB-A or USB-C plug into the device’s USB port.  
2. Wait for the device to recognize the USB flash drive. 
3. *View the USB flash drive’s contents on the device. 
4. *Transfer data from the device to the USB flash drive or from the USB flash drive to the device by dragging and dropping files. 
5. *Modify the data (create, rename, delete, move) stored on the USB flash drive using the device’s interface. 
6. Eject the USB flash drive from the device. 
7. Remove the USB plug from the USB port. 

*Read, write, and modification operations involve data flow from the device to the USB plug, controller chip, and flash memory chip (and vice versa) timed by the crystal oscillator. 

Cost 

USB flash drive price varies widely based on storage capacity, USB plug type, speed, and security features. Having more flash memory, a USB-C plug (or both USB-C and USB-A plugs on one device), faster transfer speeds, and hardware encryption corresponds to higher costs. Table 1 gives typical price ranges for USB flash drives with common feature combinations. 

Range	Features
Up to $25	Up to 256 GB USB-A flash drives
$25-$50	A 512 GB USB-A flash drive or a 256 GB USB-C flash drive
$50-$150	A 1 TB USB-A flash drive or a 512 GB USB-C flash drive
Over $150	A 2 TB USB-A or USB-C flash drive, or an encrypted flash drive

Conclusion  

USB flash drives are compact and lightweight, making them easy to carry around. They are designed to be durable and resistant to damage from physical shock, drops, and vibrations since they do not have any moving mechanical parts. They can hold any type of digital data (documents, images, videos, applications, and OSs) and support a wide range of storage capacities. Modern USB flash drives use fast data transfer protocols. 

While USB flash drives possess many benefits, they also have a few drawbacks. Because they are small, they are easy to misplace or lose. They are designed to endure wear and tear, but can still be physically damaged if crushed, bent, or exposed to water. If a USB flash drive does not have hardware encryption and software encryption is not used, anyone with access to the drive can view and modify its data. 

USB flash drives are one among many data storage solutions. They are designed to store 2 GB – 4 TB of data short-term, transfer files, and function as bootable media. Since USB flash drives have limited storage capacity and comparatively short lifespans, they are not ideal for storing more than 4 TB of data or archiving data. To store substantial amounts of data, hard disk drives (HDDs), solid state drives (SSD), or cloud storage are more suitable. To reliably store data for lengthy periods of time, consider using tape drives, which can preserve data for decades or archival-grade optical discs, to store data for hundreds or even thousands of years (Butler, 2023). 

References 

Aiibe 32GB USB Flash Drive Memory Stick Thumb Drive Black. Amazon. (n.d.). https://www.amazon.com/Aiibe-Flash-Drive-Memory-Stick/dp/B07GN6CGDF.

Bigelow, S. J. (2023, May). What is NAND flash memory? TechTarget. https://www.techtarget.com/searchstorage/definition/NAND-flash-memory. 

Butler, S. (2023, July 8). What’s the best way to store data for decades or centuries? HowToGeek. https://www.howtogeek.com/858426/whats-the-best-way-to-store-data-for-decades-or-centuries/.

But what is NAND memory and how does it work? Nexus Industrial Memory. (n.d.). https://nexusindustrialmemory.com/guides/what-is-nand-memory/.

Johnston, L. (2024, May 16). How to choose the right flash drive. Lifewire. https://www.lifewire.com/what-size-usb-flash-drive-do-i-need-2640421.

Kingston Technology. (2019, February 1). Encrypted USB Flash Drives Explained [Video]. YouTube. https://youtu.be/xf_hRTzSnvU?si=1f9iRMTreZ1PBjkH.

Navigator USB flash drive. USB Memory Direct. (n.d.). https://www.usbmemorydirect.com/products/navigator/.

Encrypted USB Drive Secure USB Flash Drive 32GB/64GB AES256-bit USB 3.0 Hardware Password Memory Stick Automatic Lock for Protection Aluminum Alloy Shell with Encryption Keypad, Flash Drive. Temu. (n.d.). https://share.temu.com/JoWUckoSRDC.

Stiemer, F. (2025, February 14). How long does data last on a USB flash drive? It’s complicated. PCWorld. https://www.pcworld.com/article/2037550/how-long-does-data-last-on-a-usb-flash-drive-its-complicated.html.

Type C flash drive, 2 in 1 OTG USB C+ USB 3.0 dual drive Waterproof memory stick with keychain metal for computer, MacBook, Google’s Chromebook pixel, Samsung Galaxy (Type-C32GB). Amazon. (n.d.-b). https://www.amazon.com/Waterproof-Keychain-Computer-Chromebook-TYPE-C32GB/dp/B082LZJ7QY.

Uncased USB flash disk / memory stick – 2 GB. Adafruit Industries. (n.d.). https://www.adafruit.com/product/5476.