How Does a Flash Disk Drive Work?
Flash memory is found in many different electronic devices, from video games to digital cameras. Due to its speed and reliability, flash memory has become increasingly popular. As a result, flash disk drives, or USB drives, have taken over floppy disks as they are smaller, faster, have much superior storage capacity. Since they have no moving parts, flash drives are also known as a solid-state storage medium.
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Essential Components
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Four essential components are typically in a flash drive. The USB connector enables the drive to be plugged into another electronic device, e.g. a computer tower block. Another component, a USB mass-storage controller, has some on-chip ROM and RAM. Thirdly, a NAND flash-memory chip is used to store data. A fourth component, a crystal oscillator, controls the drive's data output.
The Grid
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Flash memory contains a grid of rows and columns. At each intersection of the grid are two transistors, known as the floating gate and the control gate. These transistors (or gates) are separated by a thin oxide layer.
Flash drives have an EEPROM (Electrically Erasable Programmable Read-Only Memory) chip, which utilizes the grid design. The EEPROM can be deleted in blocks and must be saved before power is turned off or the drive is removed. Flash memory uses a method called tunneling to prepare the device to save and erase data from each block of space.
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Tunneling
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An electrical charge of 10 to 13 volts is sent to the floating gate, where the electrons are located. The electrons become charged and are then pushed and trapped by the oxide layer, which then gives them a negative charge. The cell sensor inside the flash drive monitors the tunneling process. This is how blocks are written to or erased.
Since the processes are done electronically, flash disk drives are much quicker than other EEPROM chips.
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- Photo Credit flash drive image by Antonio Oquias from Fotolia.com
