The micro USB plug is the smallest version of a USB plug. In addition, there is the standard USB plug and the mini-USB plug. The micro USB plug has the smallest dimensions of less than 7 mm. It is ideal for very small devices such as MP3 players, cell phones, digital cameras, etc., and is expected to replace the mini-USB plug in the medium term. The Micro-USB plug is also used as a plug for chargers, putting a stop to the manufacturer-specific variety of charger plugs.
The Micro- USB connector is relatively robust, it has a stainless steel shell, is rated for 10,000 mating cycles and meets USB 2.0 specifications, and comes in three versions as Micro-A, Micro-AB and Micro-B connectors. The USB 2.0 Micro-A is rectangular and is used on the host side. Its color is white. The USB 2.0 Micro-AB also has a rectangular design, but is gray. It is used for PC-lesscommunication between two end devices. This type of communication is called On-the-Go( OTG). The USB 2.0 Micro-B version is trapezoidal and black.
Unlike the standard USB connector, the Micro-USB connector has five contacts: Two for the positive supply voltage of +5 V and for ground, two more for the two data lines and one, pin 4, for the connector identification( ID) whether it is Micro-A or Micro-B. For Micro-A the pin is connected to ground, for Micro-B it is not connected.
Besides the mentioned Micro-USB connectors, which fulfill the specifications according to USB 2.0, there are other variants, which fulfill USB 3.0. Namely, on the one hand, there are connectors that are backwards compatible with the micro USB connectors for USB 2.0, these carry the designation USB 3.0 Standard-A, USB 3.0 Standard-B and USB 3.0 Powered-B, and three others, the actual 3.0 connectors, USB 3.0 Micro-A, USB 3.0 Micro-AB and USB 3.0 Micro-B. These USB connectors are colored blue to distinguish them from the other connectors.
The Micro-USB plug was standardized under pressure from the EU Commission and provides standardization for chargers for small mobile devices.