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Flash Drives - Components
By admin | May 20, 2007
The device is fitted on one end with a single male type-A USB connector. Inside the plastic casing is a small printed circuit board. Mounted on this board is some simple power circuitry and a small number of surface-mounted integrated circuits (ICs). Typically, one of these ICs provides an interface to the USB port, another drives the onboard memory, and the other is the flash memory.
Essential components:
There are typically three parts to a flash drive:
- Male type-A USB connector - provides an interface to the host computer.
- USB mass storage controller - implements the USB host controller and provides a linear interface to block-oriented serial flash devices while hiding the complexities of block-orientation, block erasure, and wear balancing, or wear levelling, although drives that actually perform this in hardware are rare. The controller contains a small RISC microprocessor and a small amount of on-chip ROM and RAM.
- NAND flash memory chip - stores data. NAND flash is typically also used in digital cameras.
- Crystal oscillator - produces the device’s main 12 MHz clock signal and controls the device’s data output through a phase-locked loop.
Additional components:
The typical device may also include:
- Jumpers and test pins - for testing during the flash drive’s manufacturing or loading code into the microprocessor.
- LEDs - indicate data transfers or data reads and writes.
- Write-protect switches - indicate whether the device should be in “write-protection” mode.
- Unpopulated space - provides space to include a second memory chip. Having this second space allows the manufacturer to develop only one printed circuit board that can be used for more than one storage size device, to meet the needs of the market.
- USB connector cover or cap - reduces the risk of damage due to static electricity, and improves overall device appearance. Some flash drives do not feature a cap, but instead have retractable USB connectors. Other flash drives have a “swivel” cap that is permanently connected to the drive itself and eliminates the chance of losing the cap.
- Transport aid - In some cases, the cap contains the hole suitable for connection to a key chain or lanyard or to otherwise aid transport and storage of the USB flash device.
Internals Of A Typical Flash Drive
| 1 | USB connector |
| 2 | USB mass storage controller device |
| 3 | Test points |
| 4 | Flash Memory chip |
| 5 | Crystal oscillator |
| 6 | LED |
| 7 | Write-Protect Switch |
| 8 | Space for second flash memory chip |
Source: http://en.wikipedia.org/wiki/Flash%5Fdrive
Topics: Computers & Software |