MIPI Alliance recently announced that it has completed the long-term development of the MIPI A-PHY v1.0 physical layer communication protocol. This is a serialiser-deserialiser (SerDes) physical layer specification primarily used for automotive applications. The specification is currently under member review and is expected to be officially adopted within the next 90 days. In fact, prior to this, MIPI already had a complete set of communication protocols widely used in the camera and display fields. D-PHY, C-PHY, and M-PHY are capable of high-volume physical transmission, but these physical layer protocols are unable to perform long-distance transmission, leading to usage barriers in the automotive and IoT fields.

A-PHY is designed to provide physical layer support for data transmission across the entire vehicle distance. Its maximum transmission distance can reach 15 meters, while the maximum transmission speed in the future can reach or even exceed 48 Gbps, far exceeding LVDS’s 1.5 Gbps. It will help the automotive industry accelerate the performance of Advanced Driver Assistance Systems (ADAS), Autonomous Driving Systems (ADS), and automotive surround view systems, including cameras and In-Vehicle Infotainment (IVI) displays.

In current automotive systems, high-level MIPI protocols such as Camera Serial Interface 2 (MIPI CSI-2) and Display Serial Interface 2 (MIPI DSI-2) are used to connect sensors and displays to many vehicles’ Electronic Control Units (ECUs) and other onboard computers. Currently, these systems transmit through short-distance physical layers like MIPI C-PHY or D-PHY. When long-distance transmission is required, a “bridging” solution must be used. However, the widely used bridging protocol LVDS has a maximum transmission speed of only 1.5 Gbps, which is far from meeting the development of automotive cameras and display devices, becoming one of the main constraints for new automotive functions. There are also many situations in IoT that require long-distance transmission, which cannot be resolved. A-PHY’s transmission speed is much higher than the commonly used bridging protocol such as LVDS.

A-PHY is designed for asymmetric data links in point-to-point topologies, with capabilities for high-speed unidirectional data and embedded bidirectional control data. It can also increase power transmission capabilities on the same cable. Its main core advantages are:

• Simpler system integration and lower costs: Host devices supporting MIPI CSI-2 and DSI-2 can eliminate the need for bridge integrated circuits.

• Long transmission distances: Up to 15 meters.

• High performance: Five transmission rates (2, 4, 8, 12, and 16 Gbps), with future capabilities reaching 48 Gbps and above.

• High reliability: Ultra-low 1E-18 packet error rate, achieving unprecedented reliable performance.

• High anti-interference capability: Using a unique PHY layer retransmission system, it has ultra-high anti-interference capabilities.

The first end-to-end A-PHY device may not be available until 2024. Market applications will also have a certain delay. However, from the MIPI Alliance’s white paper, we can see that the first plan is to introduce A-PHY bridging chips to replace the currently widely used LVDS chips. It is believed that this will have a significant impact on the current bridging chip market of TI and Maxim.

Ultimately, MIPI A-PHY will construct an end-to-end system designed to simplify the integration of cameras, sensors, and displays while also incorporating functional safety. By using the upcoming adaptation layer, these higher-level protocols will run natively on A-PHY, eliminating the need for these proprietary bridges.

This approach will transfer the device advantages established by the MIPI Alliance through mobile devices to automotive systems, reducing the costs and integration difficulties of automotive systems.

Non-A-PHY Situation

A-PHY Situation

According to the information obtained so far, there will be two different physical cables.

Although the main promotion of A-PHY is currently in the automotive field, I, being observant, found a logo on MIPI’s A-PHY page. This leads us to believe that A-PHY will also have significant potential in the IoT field in the future.