Electronic Design

Automotive/Convergence Sponsored by: MAXIM INTEGRATED PRODUCTS

How will the move from 12-V auto battery systems to 42 V affect the design of automotive electronic circuits?
ICs operate from 1.5 to 3.5 V, and they will operate from 1 V or less in the near future. The ideal engine-control unit (ECU) will be designed to be compatible to enable ECU manufacturers to make the transition where applicable. Devices that make this possible will be attractive to Tier 1 suppliers so they can target one module to both markets. As the module input voltage increases to 42 V, this change in power-supply topology will require dc-dc converters to step down the high voltage followed by the post linear regulators to generate the multiple rails needed in the module (Fig. 1).

Will power budget design considerations change as the result of new 42-V auto batteries?
Yes. Despite lower supply voltage ICs that consume less power, more electronics are being used in cars. In fact, the number of ICs will increase substantially over the next five years. This increase is the main reason for OEMs looking to 42 V to begin with, as alternator loads are already at their maximum capacity. Intelligent battery-monitoring systems are being implemented for load-shedding and other power-saving features. Even simple components like a remote keyless entry (RKE) system for a keyfob or keychain must be designed for minimum power consumption, even though it derives its power from its own small battery (Fig. 2).

How will an auto's operating environment influence my designs?
Autos face very harsh environments, from the frozen tundras of Alaska to the searing hot deserts of Arizona, so ICs need to handle various temperature extremes, depending on the vehicle location. Under-the-hood modules must handle -40°C to 150°C ambient conditions, with the die operating temperature running even higher. Electrical characteristics and performance specifications must be simulated, verified, and calibrated over this increased temperature range. ICs also must endure shock and vibration and acceleration/deceleration effects. Therefore, ICs and subsystems must be designed to withstand these conditions, which include package design and testing, to last for the average automotive lifetimes of at least 10 to 15 years.

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