How do micro SD cards keep having more an more memory, yet stay the same size?


How do micro SD cards keep having more an more memory, yet stay the same size?

In: Engineering

Moore’s Law states that the amount of transistors manufacturers can put on an integrated circuit doubles every 2 years or so. This means you can fit more transistors into a memory card, increasing the amount of storage in the same sized card.

Moore’s law is predicted to slow down as science is getting down to molecular level transistors which actually leak electrons.

Most of the size of a microSD card is taken up by the wiring from the contacts to the chip(s). The chip is actually a pretty small part of the card. What is happening is the chip manufacturers are constantly improving their fabrication techniques and researchers are refining the physics so we’re able to fit more ‘stuff’ onto a chip the same size. This is Moore’s Law that the other comment mentions.

Also if you did make a smaller SD card then it wouldn’t fit anything. The card manufacturers together with the device manufacturers agreed on the dimensions of the card. That way the card maker could all make cards which would fit in many different devices. And the device manufacturers could make devices which take cards from anyone. This is how standards in the electronics world work. Companies that try to buck the standard often don’t last long.

Note that they tend to be less and less reliable. That is, the data on them degrade faster.

The trick is to store more than one bit per transistor: you can charge it at 0%, 33%, 66% or 100%. Instead of the classic 0% vs 100%. You get 4 possibilities, that’s 2 bits, per transistor.

You can go crazy and store 3 bits (8 different levels). The advantage of that is that you also increase the read/write speed as a single wire can carry 2 or 3 time more information.

The issue is that you make it unreliable as you get closer to analogic instead of digital. So you reserve a little bit of your storage as redundancy. You can use self correcting encoding, like is used on CD-ROM to hide it to your customer.