FEATURE INTERCONNECTION
OPTICAL CONNECTIONS FOR AUTOMOTIVE BATTERY MANAGEMENT
Carlos Pardo CEO and co-founder of KDPOFpresents the latest optical connector for automotive E
lectric and hybrid power trains in vehicles present different voltage
domains with large level differences, such as the ECU domain with 12 Volts, the actuators domain with 48 Volts, and the electric power domain with 400 Volts. The lack of galvanic isolation between the domains of a battery management system causes a serious threat to the user and a source of severe damage to the electromechanical parts of the car. Consequently, the galvanic isolation between these domains is a must due to ground parasitic resistance and potential shorts between voltage domains. Galvanic isolation is also necessary
between the primary and secondary systems of both ac-dc and dc-dc converters due to the presence of hazardous high voltage (above 25 Vac or 60 Vdc). According to the FMVSS 305 and ECE-R standards, the isolation barrier between battery and exposed conductive parts should maintain 500 Ω/V before and after a crash impact. This is a tough requirement that is very hard to reach without a nearly perfect isolation that copper-based networks are unable to ensure. Low cost and low performance means,
to achieve galvanic isolation is an opto coupler based solution, which is rather unreliable and offers very limited speed performance. Looking at optical connections, glass optical fibre (GOF) does not provide enough margin for automotive requirements. This solution is mainly aimed at the highly- controlled environment of data centres, and does not meet automotive norms. Consequently, the first choice for
battery management systems is Gigabit Ethernet POF (GEPOF), which fully meets the requirements of carmakers by providing high connectivity with a flexible digital host interface, low latency, low jitter, and low linking time. Optical connections with POF provide the optimal means to achieve galvanic
20 NOVEMBER 2017 | ELECTRONICS
isolation, providing 100Mbps Ethernet compatible solutions with enough margin to withstand the harsh automotive environment. In addition, they are easy to upgrade to 1000Mbps when a higher data rate is required. KDPOF is a Spanish start-up company
and leader in high data-rate transmission technology. Its KD1053 is one of the first 65nm CMOS ASSP’s that implements a PCS and PMA sublayer of a 1000BASE- RHx PHY, compliant with the specifications of IEEE Std 802.3bvTM- 2017 standard for gigabit optical communications over POF. KD1053 must be connected to a compatible Fibre Optic Transceiver (FOT), which implements a PMD sublayer and a Medium Dependent Interface (MDI) to form a complete automotive 1000BASE-RHC physical layer. In addition to battery management,
Ethernet seems to be the future network technology of choice for carmakers. Traditionally, there have been two main alternatives for physical layers in
Image 1:
Applications for POF in the car range from battery management and smart antenna modules to autonomous driving and ADAS.
Copyright: KDPOF
automotive applications, optical and copper-based, with copper coming in the form of UTP (Unshielded Twisted Pair), STP (Shielded twisted Pair), or coaxial cables. Traditional copper-based networks are the default choice for new architectures because of the risks and challenges of adopting new physical media. But looking closer, copper solutions suffer from electromagnetic emissions, immunity issues, and lack of galvanic isolation, not to mention their higher weight and their unstable cost. Plastic Optical Fiber (POF), however,
fulfills all these conflicting demands, thanks to gigabit capabilities over an optical, low cost, and already qualified transmission media. It is cheaper than STP; the cost is similar to coax. Future POF costs are much more predictable and bounded than copper based solutions. POF is immune to electrical noise, which is not the case with UTP. As an optical fibre with a large core, it is able to withstand vibrations and misalignments much better than other optical or copper alternatives. POF is basically made of plastic, so its weight is much lower than the other alternatives. Finally, POF can withstand harsh
Image 2:
Optical connections with POF are ideal for galvanic isolation in battery management systems
Copyright: KDPOF
environments and tolerate conditions such as routing across the engine compartment with temperatures as high as 105ºC, for certain routing sections POF is even able to withstand up to 120°C. POF cables are very reliable compared to GOF, coax, and STP. Their good bending performance starts at a radius of 10mm, and gigabit transmission distances of up to 50 meters are possible. Well-established engineering
collaboration between key leading optoelectronic and connector vendors worldwide ensures a well-supplied and competitive market for all the components needed in the system.
KDPOF
www.kdpof.com e:
sales@kdpof.com
/ ELECTRONICS
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