ASIL-Grade Camera Power Protector Safeguards Your Car Cameras
March 17, 2020
| By: Starry Tsai
Executive Business Manager Maxim Integrated
| and Chintan Parikh
Business Director; Automotive Business Unit, Maxim Integrated
Your eyes aren't the only ones fixed on the road while you're driving these days. Modern vehicles now boast multiple cameras, which, combined with other advanced sensors such as radar and LiDAR, support safety features like advanced driver assistance systems (ADAS). The fusion of these sensors detects blind spots, pedestrians, street lanes, and more…and even guides the vehicles to park themselves. Some of today’s semi-autonomous vehicles, for instance, have 8 to 12 cameras providing 360-degree surround view for parking assist and forward visibility of 250m for collision avoidance. These cameras can work with ultrasonic sensors and a forward-facing radar to provide a more extensive field of vision.
Globally, the automotive camera market is anticipated to reach roughly $7.5 billion by 2023, with a CAGR of 24.3% from 2018 to 2023, according to a report from Research and Markets. The researchers note that demand for ADAS as well as North American and European government requirements for rearview backup cameras are key drivers of this growth. Also, cameras are starting to replace traditional side-view mirrors in some cars, and emerging driver monitoring systems rely on cameras to assess conditions like drowsiness or distraction. The move towards higher safety standards will only continue to fuel the demand for cameras.
Given that these automotive cameras play such a critical role in safety, it's imperative to ensure that they are powered properly and operate reliably. You'll also want to consider compliance to the Automotive Safety Integrity Level (ASIL). ASIL, which classifies the inherent safety risk in an automotive system, is an important part of complying with ISO 26262, which provides an international standard for safety-critical automotive components.
Figure 1. Automotive cameras that provide surround view add to the safety features of vehicles. An ASIL-grade camera protector IC like the MAX20087 can support reliable operation of these camera systems.
Balancing Power and Protection Needs
There are various power management schemes for automotive cameras—typically, the path spans from the car battery that provides the power source to the remote cameras themselves. Say you've got a 12V car battery and several cameras to power over a coaxial cable. Due to the wide voltage swings between the battery and the cabling (which is typically 8V-10V at 0.3A per camera), you will need to consider various constraints related to power over coaxial systems. You'll need a buck-boost converter to adjust for the different voltages, particularly during start-stop and cold-crank conditions. But still, you'll need to provide some isolation against fault conditions such as overcurrent, short-to-ground, and short-to-battery—all of which can cause damage and, as a result, impact driver and passenger safety. For this, you may need to develop additional hardware and software for system monitoring and/or use several discrete devices, based on the number of cameras in your system.
Better yet, you could choose a highly integrated camera power protector IC for your automotive camera module. Such a device enables you to minimize your fault mitigation circuitry by tightly controlling the maximum current per channel. You'd also be able to isolate all faults on each camera from a single power supply and from other cameras. An ideal protector IC would also provide diagnostic fault information via I2C.
The camera protector can be part of a fusion electrical control unit (ECU) for the camera system. A buck-boost converter would connect to the car battery and deliver DC power to the remote cameras through the camera protector, AC-blocking coils, and coaxial cables. A quad deserializer would connect a microprocessor to the remote cameras over a bank of AC-coupling capacitors and the same coaxial cables. Each of the remote cameras would be managed by automotive power management ICs (PMICs), the serializer, and the image sensor. Figure 2 provides a depiction of this architecture.
Figure 2. Power management architecture for automotive camera system.
Industry's Only ASIL-Grade Camera Protector
Maxim's MAX20087 provides an example of a camera protector IC that can be plugged into a remote camera system. It's the industry's only ASIL-grade camera protector (complying with ASIL B through ASIL D) with integrated I2C-based diagnostics. As a dual/quad device, it provides two or four 600mA protection switches in a 4mm x 4mm, 20-pin TQFN. A single MAX20087 supports four cameras simultaneously, while two of the devices in parallel on the same bus supports eight cameras. The device protects each output individually from short-to-battery, short-to-ground, and overcurrent conditions. An integrated 8-bit analog-to-digital converter (ADC) monitors current, voltage, and supply readings as required for ASIL compliance.
The functionality integrated into the MAX20087 saves you from having to utilize more discrete components. For example, since the device blocks short-to-battery from backfeeding to the supply rail, you won't need to add a reverse blocking diode on each channel. You can assess the MAX20087 for your next car camera design by buying the MAX20087EVKIT evaluation kit, which can operate as a stand-alone protector or be connected to a controller through an I2C interface for advanced control and diagnostics.
To round out the power management architecture for a camera system, Maxim provides various automotive power ICs. For example, the remote cameras can be supported by these automotive PMICs:
- MAX25249 and MAX25249B quad output mini PMICs, the industry's smallest such solutions for automotive cameras with precision monitoring. These devices integrate three DC-DC converters and a high-PSRR LDO in a 3.5mm x 3.5mm, 20-pin TQFN.
- MAX20049 flexible, compact, quad power supply with 2.2MHz, 500mA buck converters and dual LDOs for automotive camera modules. The two step-down converters are designed for fixed-frequency pulse-width modulation (PWM) operation with input voltages from 3.5V to 17V.
Ensuring that your car cameras are properly powered and will operate reliably is essential given the critical role that these cameras play in automotive systems. That's why the right automotive PMICs can make all the difference in your designs. Learn more on the topic by reading the article, "Provide a Safe Power Path from the Car Battery to Remote Cameras."