Electronic Design

Innovations Accelerate Automotive Change

Electronic products for automobiles improve control, safety, fuel economy, and comfort while providing home-like entertainment and connectivity. This year’s crop of enabling technologies for automotive electronics promises to make each of these areas even better in the future.

In particular, three leading-edge products will change automotive electronics design as well as the automotive environment. These innovations include power packaging with dual-side cooling, a serializer/deserializer (SERDES) chipset with high-bandwidth digital content protection, and an audio amplifier for stop/start and hybrid vehicles.

Power MOSFET Packaging
Several new automotive applications require higher power levels such as electric power steering (EPS), power supplies, battery switches on hybrid electric vehicles, and integrated starter alternators (ISAs) on micro hybrid vehicles.

International Rectifier’s automotive DirectFET2 power MOSFET offers increased power density and dual-sided cooling as well as minimal parasitic inductance and resistance for heavy vehicle loads. The package design uses a coined copper clip to connect the drain of the MOSFET to the printed-circuit board (PCB), providing improved electrical connectivity and an additional top-side cooling path (Fig. 1).

The automotive-qualified (AEC-Q100 standard) version of packaging that has been used in high-power computing applications for several years was announced earlier in 2010. Passing the thorough automotive testing required changes to the design, and at the same time, IR increased the package size.

The automotive-qualified DirectFET2 power MOSFETs are rated at a maximum junction temperature of 175°C. They also have a Moisture Sensitivity Level rating of 1 (MSL1). And, IR recently added three more products to the automotive family.

In the larger package, with a footprint that’s 60% smaller than the industry-standard D2Pak, the AUIRF7738L2 and AUIRF7737L2 have a maximum on resistance of 1.6 mΩ and 1.9 mΩ with a source-drain voltage of 40 V. In the smaller medium-size DirectFET2 package, with a footprint the same size as a 5- by 6-mm power quad flat pack no-lead (PQFN) or SO-8, the AUIRF7736M2 has a maximum on resistance of 3.0 mΩ with a similar 40-V rating.

SerDes Chipset with HDCP
When it was initially introduced earlier this year, National Semiconductor’s FPD-Link III SERDES chipset addressed the needs of automotive infotainment and driver-assist systems. For example, it could be used to transmit high-speed video data from onboard cameras to a digital display.

More recently, the DS90UH925Q serializer and DS90UH926Q deserializer represent the industry’s first SERDES chipset with high-bandwidth digital content protection (HDCP) for automotive infotainment systems. Since the chipset supports in-car distribution of protected video and audio content that meets Digital Content Protection (DCP) LLC’s specification, it enables Blu-ray movies with up to 720p resolution in the vehicle. Major content providers such as Warner Bros., the Walt Disney Co., and Sony Pictures Entertainment endorse HDCP.

A high-quality viewing experience in the vehicle is part of carmakers’ efforts to provide home quality in a mobile environment. In addition, the newest FPD-Link III SERDES chipset (Fig. 2) allows the consolidation of video and audio data and bi-directional control over a single differential pair. This reduces interconnect size, weight, and cost and further simplifies system design in automotive systems.

A unique HDCP key that’s stored in the SERDES chipset’s memory protects video content from unauthorized use. In addition, the chipset encrypts the content data. And, it makes required authentication exchanges according to the HDCP specification.

Audio Amplifier
The STMicroelectronics TDA7850LV audio power amplifier addresses issues that are created by the energy-saving engine start/stop feature. This feature, combined with other technologies such as high-efficiency engine management programs, is projected to reduce fuel consumption by as much as 20% in certain models. According to Strategy Analytics, the annual demand for start/stop systems is expected to reach almost 20 million units by 2015.

Present in micro hybrid as well as hybrid electric vehicles, the stop/start system can cause the supply voltage for on-board electrical equipment to drop as low as 6 V when the engine is turned off and restarted since the battery is the only source of electrical power.

Also, switching between battery power and alternator power can generate “pop and click” noise. Both situations detract from quality audio in the vehicle, especially as automakers strive to improve the vehicle infotainment experience.

The TDA7850LV is the first of a new series of STMicroelectronics devices (Fig. 3) designed specifically to solve these problems in these rapidly emerging types of electrical-power-supplemented vehicles. The 4x50W MOSFET output stage has a 2-Ω output driver compatible with many speaker types.

In addition, the device integrates circuitry to regulate the supply voltage and suppress pop and click noises. By not having to add external components to obtain these functions, system designers simplify their design, reduce cost, and save PCB space.

Timely innovative ICs that solve problems created by changes in other vehicle systems should become increasingly common as the pace of change in automobiles accelerates.

International Rectifier

National Semiconductor

STMicroelectronics

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