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What’s Inside A USB Drive?


Have you ever wondered what’s inside a USB? Have you ever been baffled at how this compact piece of technology, small enough to fit in the palm of your hand, can hold so much information? You may not have the means or the time to crack open a flash drive and see what’s inside, but we do. We’ve taken apart our fair share of flash drives and seen what makes them tick.

Read on as we break down what’s inside a USB drive.


Essential Components

All USB drives are comprised of five essential components. Without them, a flash drive could not hope to function. These five components are:

  • Standard USB Plug
  • USB Mass Storage Controller
  • NAND Flash Memory Chip
  • Crystal Oscillator
  • Cover

Standard USB Plug

This is the external part of the drive that forms a physical interface with the host (i.e. your computer). They tend to be flat and rectangular in shape. The “male” part of the USB connector that slides into the computer is called a plug; the female connector that can link to other cables and devices is called the port (though sometimes it’s called the receptacle).

Most USB plugs are Standard-A connectors. These are the classic USB Type A devices. Plugs are also available as Type-B, Mini-USB, Micro-USB, and USB Type-C.

USB Mass Storage Controller

This is a small microcontroller inside the USB that makes your device accessible to a host’s system and enables file transfers between the host and USB device. The microcontroller is essentially a middleman facilitating the data transfer. It contains a small amount of on-chip ROM and RAM.

Both ROM and RAM chips deal with data storage, but there’s a crucial difference between them: ROM is non-volatile storage while RAM is volatile. If both of them were volatile, your flash drive wouldn’t be able to hold onto your data. Volatile storage requires a constant source of power in order for it to retain information. When the power is off or the device is pulled out of a host, the RAM chip would lose any information stored on it. A ROM chip, however, is different: as a non-volatile chip, it would retain the data regardless of whether or not it was connected to a power source.

NAND Flash Memory Chip

NAND flash memory is another form of non-volatile data storage. The NAND chip in USB drives is the backbone of the device, giving it the power and storage space it needs to hold onto your information. Your USB drive would barely be able to hold a receipt without it, let alone gigabytes of documents.

Crystal Oscillator

This part of the USB drive controls the flow of information within the USB drive. It uses a 12 MHz clock signal to control the device’s output. All electronic devices use a clock signal. The signal functions in a manner similar to a pendulum, oscillating from one end to the other. This signal helps coordinates the actions of all the electronics on the USB drive.


This is the “body” of the USB drive. It is the hard outer shell that protects the “guts” of the drive. It’s also the part of the USB drive that gets customized and styled to give USB drives their distinctive appearances.

Additional Components

All USB drives contain those five essential parts, but they also occasionally contain additional components that add extra features and functionality to your USB drive.


Some drives come with LED indicator lights. These can come in handy, as they’ll let you know when the drive is in use or being charged. LEDs are a great way to quickly and accurately monitor the status of your USB drive.

Unpopulated Space

Drives can also sometimes come with additional room inside the drive. That extra space is usually left open so a second memory chip can be added to bulk up the information storage capacities of the drive.

Transport Aid

Consider this the “convenience” component. This is the part of the USB that makes it easy to carry around. It can be a keyhole or built-in loop, a keyring, or anything else that makes it possible to clip or attach your USB for transportation.

USB Connector Cap

Some drives include a USB connector cover or cap to offer additional protection for your flash drive. These caps are designed to cover the open plugs of your USB drives, preventing dust or other damaging particles from getting inside. USB drives can also include swivel covers to protect your connectors. Sometimes the “cap” can be the cover of the USB itself, if the connectors are retractable from inside the body of the drive.

Write-Protect Switches

This is an added security feature for USB drives. Write-protect switches are a way to safeguard and preserve the integrity of your data. The switches can enable or disable the writing of data into memory. So, for example, if you were to plug your USB into a potentially unreliable source, you could switch on write-protect mode to prevent additional data from getting onto your USB drive.

Jumpers/Test Pins

These are used for testing during the manufacturing of certain USB drives. They’re used to test for flaws, as well as to ensure that everything inside the USB drive is working properly. They also help load code onto the drive’s microcontroller during the manufacturing process. If your drive is missing test pins or jumpers, don’t worry about it: not all models need or use them.

How Your USB Drive Works

Now that you know what all the parts in your drive are, you may be wondering how USB drives work in the first place! Let’s break down how the average flash drive works: it’s a lot like plumbing.

The Flow Of Data

Picture water running through a pipe. Now imagine that is data flowing through your USB drive! A USB drive functions a lot like a transistor, but one that stays switched on all the time. If you don’t know how a transistor works, they function a lot like pipes, but for energy. A typical transistor is composed of 3 parts:

  • Source: The part of the transistor where electricity and power flow into it (like water entering the opening of a pipe).
  • Drain: The part of the transistor where all that energy is expelled (like water flowing out of a pipe).
  • Gate: A section in-between the source and drain that regulates the flow of energy passing between the two points (like the shut-off valve on a pipe that controls the flow of water). When the gate is shut in a transistor, the energy shuts off.


What makes flash drives unique in comparison to standard transistors is that they come with a second gate. This second gates comes on top of the first one. The purpose of this second gate is to trap energy & data inside it, so that even when the first gate is closed and the power is shut off on the drive, that information is retained on the drive. To use our pipe analogy one more time: the second gate traps water inside the pipe, ensuring that it doesn’t get lost or flow back out.

This is why USB drives have both ROM and RAM chips. Using a combination of volatile and non-volatile storage, they are able to ensure a steady flow and transfer of information. The second gate in the drive keeps your information on-board, so even if your drive stays unplugged and powerless for months at a time, you can still retrieve any information stored on it.

In Conclusion

It can sound pretty technical, but most flash drives can be summed up and put together with only a handful of components! They are simple but extraordinarily useful pieces of technology, a form of electronics that is essential in our data-driven age. If you have any more questions about what goes on inside a USB drive, drop us a line at Premium USB. We’d be happy to answer your questions.