MIPI A-PHY®

General Info

• Overview

  MIPI A-PHY^® is a long-reach serializer-deserializer (SerDes) physical layer interface for automotive applications, including ADAS, ADS and other surround-sensor applications, including cameras and in-vehicle infotainment (IVI) displays.

  The specification provides an asymmetric data link in a point-to-point or daisy-chain topology, with high-speed unidirectional data, embedded bidirectional control data and optional power delivery, all over a single cable. This reduces wiring, cost and weight, and allows designers to optimize systems for the performance, cost and complexity required by their use cases, providing scalability and flexibility to meet a broad range of speed and design needs. For integration with existing network backbones, A-PHY complements Ethernet, CAN, FlexRay and other interfaces.

  In addition to automotive uses, the specification can be well-suited for applications such as IoT and industrial.

  MIPI A-PHY was developed by the MIPI A-PHY Working Group and is available to MIPI Alliance members. A-PHY v1.0 was also adopted as an IEEE standard in June 2021 and is available as IEEE 2977-2021. 

  For information about becoming a member, see Join MIPI.

• MASS Framework

  MIPI A-PHY serves as the foundation of an end-to-end connectivity framework, MIPI Automotive SerDes Solutions (MASS), designed to simplify the integration of cameras, sensors and displays, while also incorporating functional safety and security. Higher-layer MIPI protocols, such as Camera Serial Interface (MIPI CSI-2^®) and Display Serial Interface (MIPI DSI-2℠), are already used to connect sensors and displays to domain ECUs and other onboard computers in many vehicles. They typically are transported over MIPI C-PHY℠ or D-PHY℠ shorter-reach physical layers and use "bridge" solutions to connect to proprietary long-reach PHYs. With the use of adaptation layers, these higher-layer protocols can now run natively over A-PHY, eliminating the need for these proprietary bridges.

• Latest Versions

  A-PHY v2.0 doubles the supported baud rate from 4 GBaud to 8 GBaud, enabling support of two more downlink gears at 24 Gbps and 32 Gbps over a single cable, and enhancing the current 12 Gbps and 16 Gbps gears to support PAM4. Version 2.0 also adds an uplink gear supporting 1.6 Gbps.

  With these additions, A-PHY v2.0 addresses the increased bandwidth required by automotive zonal architectures, and enables a 1G Ethernet control channel with up to 32 Gbps video stream.

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  Version 1.1.1 of the A-PHY specification applies all corrections in the Errata 01 for A-PHY v1.1, and replaces deprecated technical terms with more inclusive wording.

  MIPI A-PHY v1.1, adopted in 2021, introduced several enhancements and is fully backward compatible with v1.0, allowing devices using both releases to coexist on the same network.

  A-PHY v1.1 doubled the total downlink data rate supported by A-PHY from 16 to 32 Gbps by adding support for Star Quad (STQ) shielded dual differential pair cables that provide dual differential pairs of conductors within a single shielded jacket. This enables two A-PHY ports over a single cable, saving cost, weight and complexity compared with using two separate coaxial or shielded twisted pair cables.

  A-PHY v1.1 also added optional PAM4 encoding for downlink gears G1 and G2, with data rates of 2 Gbps and 4 Gbps, respectively. PAM4 encoding features lower modulation bandwidth for sub-1 GHz operation, allowing manufacturers to more easily migrate to A-PHY while using either legacy cables on current platforms or lower-cost cables on new platforms.

  In v1.1, the maximum uplink data rate doubled to 200 Mbps, providing more bandwidth for command and control of automotive peripherals.