microSD card
The microSD card is a miniaturized SD card. The small memory card is extremely compact and has dimensions of only 11 mm × 15 mm. It is available in three versions with different memory sizes and speed classes. The standard version is microSD, and there is also microSDHC, which stands for High Capacity, and microSDXC, which stands for Extended Capacity.
The storage capacity of microSD cards depends on the version. microSD is available with storage capacities from 8 MB to 2 GB, microSDHC with 4 GB to 32 GB and microSDXC from 64 GB to 2 TB.
To increase the data rate, microSDHC cards and microSDXC cards have a faster data bus with Ultra High Speed( UHS), which increases the data transfer rate. microSDHC and microSDXC memory cards come in four speed classes 2, 4, 6 and 10. The speed class indicates the minimum write speed. Class 2 has 2 MB/s, Class 4 has 4 MB/s, Class 6 has 6 MB/s and Class 10 has 10 MB/s. The write speed is 66 times higher for Class 10, 40 times higher for Class 6, 26 times higher for Class 4, and 13 times higher for Class 2 than the base data rate of 150 KB/s. As for read speeds, data rates of 60 MB/s (x400) and 90 MB/s (x600) are achievable.
For microSD cards with UHS bus, the memory card and the end device have to support the UHS bus. SD memory cards are marked for both speed classes and UHS classes. microSD cards are used in smartphones, digital cameras, camcorders and MP3 players because of their small dimensions and low weight. Via adapters, microSD cards can also be operated in SD card slots.