AUTONOMOUS & CONNECTED VEHICLES
Protecting autonomous vehicle control circuits JAMES COLBY, PRASAD TAWADE LITTELFUSE, INC.
The subsystems that make up an autonomous vehicle should be bullet-proof when it comes to electrical interference and transients. Those who follow autonomous vehicle technology are usually well aware of its benefits. But the safety and convenience autonomous vehicles offer can only come if the vehicle electronics is reliable and robust to electrical shocks such as lightning strikes (limited to the ac input of on-board chargers), in-vehicle power surges, and electrostatic discharge (ESD). Designers must incorporate circuit protection early enough in the design process to avoid last-minute revisions that can delay compliance approvals and potentially compromise circuit performance.
First consider the case of the camera subsystem. Among other things, multiple cameras work together to provide depth perception and convert visual light through a CCD/CMOS image sensor into electronic signals sent to a communication and control circuit. Of the circuit blocks in a camera subsystem, those that require protection components connect with external circuitry. They typically include a CAN transceiver, the power supply, and an Ethernet transceiver. The camera power supply subsystem requires protection from over-currents, high-energy transients, and ESD. A fuse provides over-current Typical camera system protection. Designers can select either make-up on an a conventional one-time blow, ceramic autonomous vehicle.
Typical automotive camera subsystem Technology
12 V
Power supply
1
Fuse PPTC
1
TVS diode Varistor Schottky diode
CAN
CAN transceiver
2
ESD protection Control unit (DSP)
Ethernet
Ethernet transceiver
Serializer
4
CCD/CMOS imaging module
2
Diode arrays
3
Polymer and silicon ESD diode
4
Diode arrays
3 Image sensor Legend
20
DESIGN WORLD — EE NETWORK
8 • 2020
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