As we have stepped into the Digital Era, the data and information have became one of the most important things in life. Strictly speaking, we depend on data like we do on our brain. And storing these tons of data securely is the biggest issue. Here comes the role of Secure Digital storage devices e.g. SD(Secure Digital) card, SS(Solid State) drives, Flash drives, Pen Drives, micro SD cards etc.
You must have used these storing devices, but did you ever wondered how come these tiny chips let you enjoy colorful pictures and videos and other information when inserted into your mobile phones , camera, tablets, PCs etc.? Don't worry here we are to inform you.
Before diving into it, we must be aware of some fundamentals of Digital Storage.
- Digital storage devices store data in the form of bits i.e. 0 and 1. For example, suppose we have to store an alphabet 'G', then it will be converted into a code containing a series of 0 & 1, also known as ASCII(American Standard Code for Information Exchange) code. Every single character on your keyboard has predefined ASCII code. when you click a key, computer identifies that key with ASCII code only, it has nothing to do with that alphabet structure.
- 0 and 1 are just power ON and power OFF respectively like we see in a switch. 0 corresponds to low voltage(0ff) and 1 corresponds to high voltage(on). High voltage means charge is present at that bit of storage device and low voltage means absence of charge at that point.
- For switching purpose, Transistors are used. Particularly, modified version of MOSFET i.e. Floating Gate MOSFET or FGMOS are used in digital storing devices. You can click on this link to dive into the working of Transistors.
- You might be surprised that the tiny SD card you insert in your phone actually contains thousands of tiny Transistors.
For the sake of understanding, you can visualize the Transistor as a way for electrons passing from one Terminal to other and in the middle there stands a Gate which allows or forbids the flow. In case of FGMOS, when the GATE allows the flow from source to drain for about 50 milliseconds, some Electrons are trapped into the floating gate (like in a jail) in a particular fashion. The electrons trapped constitute a high voltage where electron is absent and a low voltage, where it's present similar to the ASCII code using 0 and 1. This way a storage drives store the data. The floating gate is surrounded by a non conducting layer of Metal Oxide, so the trapped electrons can remain there and retain the data even after decades.
The gate is applied with negative voltage in case of data deletion or formatting thus vacating the Floating Gate for newer data. As these chips have no moving parts, these are pretty long lasting.
I hope, now you are aware of the modern day Secure Digital(SD) data storage devices and their working.
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