In-vehicle camera trends and accompanying technical challenges

In recent years, the market scale of in-vehicle cameras has been expanding. In-vehicle cameras are used in various applications such as ADAS (advanced driver assistance system), DMS (driver monitoring system), abandoned vehicle detection, face recognition, etc., and the number of cameras installed in a single vehicle is increasing.

Under these circumstances, one of the trends of in-vehicle cameras is higher resolution. Until now, the number of pixels in in-vehicle cameras was around 1-2​ ​MP, but in order to achieve clearer images, it is believed that 2-5​ ​MP or more will become mainstream in the future.

In-vehicle camera resolution trends

Along with the improvement of image quality, there is an increasing sense of challenge in the transmission of large amounts of data.

Analog Devices provides "GMSL (Gigabit Multimedia Serial Link)" as a communication interface capable of high-speed transmission of large amounts of data. This technology is attracting attention because it can transmit high-definition video with a simple circuit.

Click here for more information about GMSL

​Another trend in automotive cameras is miniaturization. In order to implement many in-vehicle cameras, the size limit per camera is becoming stricter. In addition, there is an increasing number of cases where cameras are embedded in inconspicuous places, such as the A-pillars at both ends of the windshield, so that they are not conscious of shooting, and there is a need for further miniaturization.

Therefore, a power supply system based on PoC is expected.

Review ~ What is PoC ~

Let's check what kind of technology PoC (Power over Coax) is.

In conventional power supply systems, video signals and power are transmitted on separate cables. As the number of installed cameras increases, the number of cables increases by two, making miniaturization difficult, increasing cable costs, and increasing fuel efficiency due to the weight of the cables.

On the other hand, in the PoC system, power is superimposed on the signal cable, and the video signal and power are transmitted over a single coaxial cable. Since there is no need to install a separate power supply cable and the connectors for connection can be consolidated, the amount of wiring can be greatly reduced, and the size, cost, and weight can be reduced to improve fuel efficiency at once.

PoC is attracting attention as a technology that contributes to the miniaturization of in-vehicle cameras, and is being adopted.

■Power over coax

・Transmission of power through coaxial cables

・A transmission method that superimposes the power supply on the signal cable and eliminates the need for a separate power supply cable.

　

■ Target

・GMSL, FPD Link, GVIF

In the GMSL PoC application,

-High speed serial data

-UART/I2C commands,

-DC power

are all on the coaxial cable.

⇒Power over coax power supply has high Vout, and considering load dump, power cannot be supplied by step-down DCDC.

Performance of power supply IC required for PoC of in-vehicle camera

What kind of power supply IC is required for PoC of an in-vehicle camera?

In-vehicle cameras typically consist of two boards. The camera module is equipped with a camera, and the camera control unit (ECU) performs video processing. The images captured by the camera module are transmitted to the ECU via a coaxial cable. Meanwhile, power is input from the main battery to the ECU, and then transmitted from the ECU to the camera module.

The picture below shows the ECU on the left and the camera module on the right.

The parts surrounded by red frames are the three types of ICs required for PoC. A power supply for PoC and a camera power supply protector are placed on the ECU. The power supply for the camera is placed on the camera module.

Let's take a look at what roles and performance are required of each.

Analog Devices Power Lineup for Automotive PoC

Now, let's take a look at what the specific solutions are.

Analog Devices has multiple lineups for each of the three types of ICs mentioned above.

We will introduce representative solutions for each.

[Power supply for PoC] Easy-to-design buck-boost converter "MAX25239/40"

An example of a PoC power solution is the MAX25239/40 buck-boost converter with step-up and step-down functions. With a wide input voltage range of 2-42V, it has a withstand voltage of 36V or higher, which is required for automotive primary power supplies, and is also compatible with cold cranks.

 

A typical buck-boost converter requires four external FETs, which tends to expand the board and complicate the design. Also, the longer the wiring, the greater the radiation noise.

 

All FETs are integrated in the MAX25239/40, simplifying the wiring design and facilitating miniaturization. In addition, it has high efficiency and excellent noise performance, so it can realize low noise in-vehicle PoC that does not generate heat easily.

[Camera power supply protector] "MAX20086~89" compatible with ASIL B/C/D

A typical example of camera power supply protector is "MAX20086-89" corresponding to ASIL B/C/D.

　

Various diagnostic functions such as overvoltage/undervoltage diagnosis and short circuit diagnosis are provided, and status monitoring is possible via the I2C interface.

　

By simply placing the MAX20086-89, it is possible to easily implement optimal protection functions for automotive applications that require reliability such as ADAS.

[Power supply for cameras] "MAX20019/20" that can pursue miniaturization to the limit

One example of a camera power solution is the MAX20019/20​ ​2-channel output, 17V step-down converter. It supports 16-17V withstand voltage required for camera power supply.

 

The device size is extremely small at 2 mm × 3 mm, allowing for compact circuit designs. Since a fixed output voltage can be selected from a wide variety of options, external components for voltage adjustment can be reduced and miniaturization can be pursued to the utmost. It also has a spread spectrum function that can reduce noise.

 

It is the best power supply solution for camera modules that require strict miniaturization.

The figure below shows an example of a configuration in which two​ ​MAX20019s are used to supply 4 lines of power. A 4-channel solution is also possible, but using two 2-​channel solutions provides more flexibility and easier component layout.

 

In this article, we introduced the types of power supply ICs required, the required performance, and representative solutions from Analog Devices for PoC of in-vehicle cameras.

 

ADI's PoC solutions contribute to the miniaturization, noise reduction, and heat management of automotive cameras. We have evaluation boards for the solutions introduced. Please feel free to contact us.

 

Application example

・ADAS (Advanced Driver Assistance System)

・In-vehicle camera module

Inquiry

If you have any questions regarding this article, please contact us below.