# USB 2 Micro-A plug > the USB Micro plug used in hosts and carrying only USB 1–2 and power, replaced by the USB 2 Type‑C plug **Wikidata**: [Q102144888](https://www.wikidata.org/wiki/Q102144888) **Source**: https://4ort.xyz/entity/usb-2-micro-a-plug ## Summary The USB 2 Micro-A plug is a legacy USB connector designed for host devices, capable of carrying USB 1.0 through USB 2.0 data signals and power. It is characterized by a rectangular shape and a white insulator, serving as the compact successor to the USB Mini-A plug. This connector type has been effectively retired and replaced by the USB Type-C plug. ## Key Facts - **Official Name:** USB 2.0 Micro-A plug. - **Function:** Serves as a host-side connector carrying USB 1–2 data and power. - **Replaces:** USB Mini-A plug. - **Replaced By:** USB-C plug (specifically the USB 2 Type-C plug). - **Compatibility:** Connects with USB 2 Micro-AB receptacles and USB 3 Micro-AB receptacles. - **Pin Configuration:** Features 5 pins: VBUS (Pin 1), D− (Pin 2), D+ (Pin 3), ID (Pin 4), and GND (Pin 5). - **Visual Identification:** Distinguished by a required white insulator color inside the connector shell. - **Instance Class:** Classified as a USB 2 Micro plug and a USB Micro-A plug. - **Distinctions:** Different from the USB 2 Micro-B plug, USB 2 Standard-A plug, and USB 3 Micro-A plug. ## FAQs ### Q: What is the difference between a USB 2 Micro-A plug and a Micro-B plug? A: The USB 2 Micro-A plug is designed for host devices and features a white insulator, whereas the Micro-B plug is typically used for peripheral devices. The Micro-A plug serves as the "A" side of a connection, acting as the host or power source. ### Q: Can a USB 2 Micro-A plug fit into any USB Micro port? A: No, it is designed specifically to fit into USB Micro-AB receptacles. It is mechanically distinct from the more common USB Micro-B ports found on many older smartphones and peripherals, though the visual difference is subtle. ### Q: Is the USB 2 Micro-A plug still used in modern devices? A: No, it is considered a legacy connector. It has been replaced by the USB Type-C plug, which handles both host and device functions in a reversible format. ### Q: What is the purpose of the ID pin in the USB 2 Micro-A plug? A: The ID pin (Pin 4) allows the connector to support USB On-The-Go (OTG) functionality, helping the system identify the device's role (host or peripheral) when connected. ## Why It Matters The USB 2 Micro-A plug represents a specific, transitional phase in the evolution of mobile connectivity standards. Before the widespread adoption of the reversible USB Type-C connector, the industry sought to reduce the physical footprint of USB ports on mobile devices. The Micro-A plug was introduced as the host-side component of this strategy, replacing the bulkier USB Mini-A plug. Its significance lies in its role within the USB On-The-Go (OTG) ecosystem, which allowed mobile devices to act as hosts for peripherals like flash drives and keyboards. While the connector itself had a relatively short lifespan, it bridged the gap between the early Mini-USB era and the modern Type-C era. The specification's requirement for a white insulator to distinguish it from the black-insulated Micro-B plugs highlights the stringent identification standards required for complex USB protocols. Ultimately, the USB 2 Micro-A plug paved the way for the multifunctional, high-speed capabilities now standard in USB Type-C technology. ## Notable For - **Host Identification:** Being the specific "Micro" form factor designated for host controllers rather than peripherals. - **White Insulator:** Being one of the few USB plugs legally required by specification to use a white color insert for visual identification. - **OTG Support:** Containing the ID pin necessary for USB On-The-Go protocols, distinguishing it from standard charging cables. - **Obsolescence:** Being one of the few USB form factors completely replaced by the universal USB Type-C standard in modern host designs. ## Body ### Design and Specifications The USB 2 Micro-A plug is a rectangular connector defined by the USB 2.0 specification and subsequent legacy revisions. Officially termed the "USB 2.0 Micro-A plug," it is designed to plug into USB Micro-AB receptacles. The connector shell houses a white insulator, a mandatory visual indicator specified to help users distinguish it from the USB Micro-B plug (which typically uses a black insulator). The connector assembly consists of 10 leads (wires/contact paths), though it utilizes a 5-pin interface for its primary logic: 1. **VBUS (Pin 1):** Red wire, provides +5V power supply. 2. **D− (Pin 2):** White wire, data negative. 3. **D+ (Pin 3):** Green wire, data positive. 4. **ID (Pin 4):** Connected to ground in the plug; used for identifying the default host role in OTG configurations. 5. **GND (Pin 5):** Black wire, ground. ### Evolution and Legacy The USB 2 Micro-A plug was introduced to succeed the USB Mini-A plug, offering a slimmer profile for increasingly thin mobile devices. It was part of the "Micro" series intended to be more robust than the Mini series. However, the USB 2 Micro-A plug is now classified as a legacy component. It has been replaced by the **USB 2 Type-C plug** (and the broader USB-C standard), which consolidates host and device functions into a single, reversible connector type. Despite its replacement, the Micro-A plug remains an important part of USB history for defining early mobile host connectivity. ### Related Connectors The USB 2 Micro-A plug exists within a family of related connectors: - **USB 2 Micro-B plug:** The device-side counterpart, visually similar but with a different insulator color standard and slightly different geometry (trapezoidal vs. rectangular). - **USB 3 Micro-A plug:** A wider, usually blue-insulated connector that supports higher data transfer speeds (Superspeed) and carries additional pins, distinct from the USB 2 version. - **USB Mini-A plug:** The immediate predecessor, larger in size and similarly deprecated. ## References 1. [Source](https://www.usb.org/document-library/usb-31-legacy-cable-and-connector-revision-10) 2. [Source](https://www.usb.org/document-library/universal-serial-bus-31-legacy-connectors-and-cable-assemblies-compliance-document) 3. [Source](https://www.usb.org/document-library/usb-32-revision-11-june-2022) 4. [Source](https://www.usb.org/document-library/usb-type-cr-connectors-and-cable-assemblies-compliance-document-rev-21b) 5. [Source](https://www.usb.org/document-library/usb-type-cr-cable-and-connector-specification-release-24)