Micro SD cards are one of the smallest removable flash memory card formats designed specifically for small devices, mainly used as phone memory. Smaller than miniSD cards, and also based on the SD card format, microSD memory cards measure roughly 15mm x 11mm in size - about the size of a little finger fingernail.Older devices support only Micro SD cards while the latest devices support both Micro SD cards and Micro SDHC cards.
Micro SD cards can also be used in SD-compatible devices via an SD adapter. Micro SD cards are becoming increasingly popular because they are so small and slim and mobile phones and the minute MP4 video players are increasingly using this innovative space saving technology.
A Micro SD card's speed is measured by how quickly information can be read from, or written to, the card. In applications that require sustained write throughput, such as video recording, the device might not perform satisfactorily if the SD card's class rating falls below a particular speed.
In early SD cards, the speed was measured with the "Ã—" rating, which compared the average speed of reading data to that of the original CD-ROM drive. Currently, the official unit of measurement is the Speed Class Rating, which guarantees a minimum rate at which data can be written to the card.
The newer families of SD card improve card speed by increasing the bus rate. Whatever the bus rate, the card can signal to the host that it is "busy" until a read or a write operation is complete. Compliance with a higher speed rating is a guarantee that the card limits its use of the "busy" indication
Different Speed Classes
The Speed Class Rating is the official unit of speed measurement for SD cards. The class number guarantees a minimum write speed as a multiple of 8 Mbit/s (1 MB/s)
These are the ratings of all currently available cards:
Class 2 : 2 MB/s Speed
Class 4 : 4 MB/s Speed
Class 6 : 6 MB/s Speed
Class 10 :10 MB/s Speed
Common applications for Speed Classes
Class 2 : H.264 video recording, MPEG-4, MPEG-2 video recording
Class 4: MEPG-2 (HDTV) video recording, digital still camera (DSC) consecutive photo shooting
Class 6: Mega-pixel DSC consecutive photo shooting, professional video camera
Class 10: Full HD video recording, HD still picture consecutive shooting
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