Today’s car infotainment systems share little similarity with the radios in early cars. When first used, car radios were simplistic; nothing more than just analog radios. Today, however, modern infotainment systems provide far more than just music and news to the driver and their passengers. Besides playing music from storage devices like SD cards and USB drives, radios can play various frequency bands, covering both analog and digital broadcasts. In addition, mobile devices can now connect to infotainment systems via Bluetooth to play music and make phone calls, providing seamless integration from your personal device to your car.
Powerful navigation systems, meanwhile, now come as standard in modern cars, using GPS and real-time data from the internet to find the fastest route for the driver. However, the use of an internet connection is not exclusively there for the navigation system. Some cars provide a Wi-Fi access point so passengers can browse on their phones during the trip. The number of features and functionalities is increasing for every new generation of infotainment systems, but one thing stays the same: a stable and reliable power source is needed under all operating conditions. This article focuses on the power tree which is needed to supply a state-of-the-art infotainment system. It presents different challenges when designing this kind of application and shows a built and tested power management reference design.
A modern infotainment system has several loads which need to be powered with typically two different supply voltages needed as a main power source. The reference design discussed in this article provides one rail with +3.3 V @ 3.0 A (6.0 A peak) and +7.5 V @ 1.5 A (2.5 A peak). With the +3.3 V rail, loads like the tuner and microprocessors can be supplied either directly or by subsequent low-voltage point-of-load (POL) converters. The rail with +7.5 V for example is used for microphone phantom biasing of the hands-free set and active noise cancellation, active antennas (FM, AM, GPS, DAB), rear view camera and a CD player.