MIPI Phone Alliance Standard Aims at Automotive Sensors

January 1, 2019

Terry Costlow

Smartphones may expand their burgeoning role in the automotive industry. The MIPI (Mobile Industry Processor Interface) Alliance, which created interface standards for smartphone cameras and displays, plans to have a high-speed automotive standard ready by the end of next year. MIPI’s Automotive Working Group plans to complete the MIPI A-PHY, a physical layer specification that moves data from cameras, radar and lidar at 12-24 gigabits per second (Gbps). The group is also developing 48 Gbps technology for displays and other systems.

The group now plans to complete the document late in 2019, so it won’t show up on vehicles for a few years. Matt Ronning, MIPI Automotive Working Group Chairman, noted that this timeframe fits well with the industry’s need for very high bandwidth communication lines. “The real demand comes with autonomous vehicles that will have from 9 to 16 cameras plus radar and lidar,” he said.

The MIPI spec will be complementary to the industry’s shift from CAN to Ethernet, which provides the bandwidth needed when several ADAS systems work together. The interface that’s used for most smart phone cameras provides high speed, but developers must overcome a number of hurdles, particularly in signal-line length.

“Gbit Ethernet is coming next year for cars, but in phones, MIPI is already providing 10 Gbits/second,” said Rick Wietfeldt, MIPI Alliance board member and former chair, MIPI Technical Steering Group. “Mobile is leaps and bounds ahead in speed, but they’re looking at lengths of 15 cm, while automotive needs 15 meters.”

Today, most automotive sensor systems use proprietary interfaces, Lefkin said. Some data links provide power, while others don’t. A faster standard will help developers meet the demands that will come when larger numbers of high resolution sensors transmit data to centralized controllers. “Cameras and radar are really driving the data rates now,” said Peter Lefkin, Managing Director of the MIPI Alliance. “Requirements are going up quickly. A lot of cameras today have 2 Mpixel resolutions, in the fairly near future, they will be going to 8 Mpixels.”

Along with the length of signal lines, automotive applications have more stringent functional safety and electromagnetic coupling requirements. Functional safety introduces a bit of overhead, which must be looked at the earliest stages of standard development, Wietfeldt said. Developers are also looking closely at crosstalk, which can be an issue when many high-speed lines are routed into electronic control units.

Most automotive semiconductor suppliers are members of the Automotive Working Group along with a number of design tool providers and Bosch. Since the consortium was founded in 2004, its membership has grown to more than 300 companies.