Multi-channel synchronous buck converters for car applications

November 12, 2015 // By Jeff Gruetter, Linear Technology
As automobiles continue to add a higher density of electronic systems to enhance safety, comfort, efficiency and performance, it is not surprising that they require both smaller and higher performance power conversion solutions. These new multi-channel power management solutions need to deliver up to four independent power rails usually to power VCORE, VI/O, VMEM required for microprocessors and generally a fourth 5V rail to power a CAN transceiver.

According to Strategy Analytics, “The demand for enabling semiconductor devices is expected to grow at a compound average annual growth rate (CAGR) of five percent over the next seven years, with the total market worth over $41 billion by 2021, compared to $30 billion in 2014.” They also identified that demand for microcontroller and power semiconductors will drive over 40 percent of revenues.

Strategy Analytics provides a very quantitative description of forecasting the growth of electronics content in automobiles, but more interesting is the prevalent role that power ICs play in this growth. These new power ICs must provide:

  1. Multiple voltage rails from a single power management IC
  2. Robust performance across a wide range of voltages, including cold-crank and stop-start scenarios from <4V to load dump transients in excess of 36V
  3. Outputs ranging from 5V down to less than 1V
  4. Ultralow electromagnetic interference (EMI) emissions
  5. The highest efficiency possible to both minimize thermal issues and optimize battery run-time
  6. Ultralow quiescent current (<10uA per channel) to enable always-on systems such as security, environmental control and infotainment systems to stay engaged without draining the vehicles battery when its engine (alternator) is not running.
  7. The smallest solution footprints, often requiring multiple voltage rails to minimize space required for power conversion circuits
  8. Switching frequencies of 2MHz or greater to keep the switching noise out of the AM Radio band and to keep solution footprints very small

The goal of the increased performance levels of power ICs is to allow the design of increasingly numerous and complex and electronic systems found within automobiles. Specific applications which are fueling the growth for electronic content in cars are found in every aspect of the vehicle. For example, new safety systems including lane monitoring, adaptive safety control, automatic turning and dimming headlights. Infotainment systems (telematics) which continue to evolve and pack more functionality into an already tight space must support an ever growing number of cloud based applications.

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