Active antenna driver for car infotainment systems: Page 2 of 4

June 12, 2014 //By Bernd Stein, Infineon
Active antenna driver for car infotainment systems
The days of simple car radios using large telescope antennas are over. Nowadays cars are equipped with full featured infotainment or multimedia systems. While the AM/FM radio is still a part of the system, features like digital audio broadcasting (DAB), HDTV, satellite radio, integrated cell phones, CD/DVD/MP3 players, GPS navigation or video game systems are added.
shipped in high volume. The new voltage regulator provides several enhancements like better accuracy (of VQ & current monitor), higher output current and less external components. The TLF4277-2 is a monolithic integrated low drop out voltage regulator (figure 2) capable of supplying loads up to 300 mA. For an input voltage up to 40 V the TLF4277-2 provides an adjustable output voltage in a range from 5 V up to 12 V. The integrated current monitor function is a unique feature that provides diagnosis and system protection functionality.

Fig. 2: Simplified block and application diagram of the TLF4277-2

Fault conditions such as over-tem­perature and output overvoltage are monitored and indicated at the current sense output. The maximum output current limit of the device is adjustable to provide additional protection to the connected load. Via the enable function the IC can be disabled to lower the power consumption. Other features are a low dropout voltage (typ. 100 mV) and very low power consumption (typ. 150 µA at 25°C).

Accurate antenna status monitoring is provided by very accurate current sense, with a continuous monitoring of the load. Compared to other solutions with current sense accuracy in the range of 10 to 30 percent, the TLF4277-2 provides accuracy (current monitor factor) as high as 5 % across the full range of output current. Compared to previous solutions the output voltage tolerance is also improved (2 % compared to 3 - 5%). The adjustable maximum current limitation in the range of 10 mA to 300 mA improves amplifier lifetime. The digital status output signal shows if one or more of the monitored protection functions (over current, over voltage or temperature shutdown) is activated.

The TLF4277-2 needs less external components reducing the related PCB space. No external shunt is needed, which results in optimized systems costs. Reduced component count is a critical aspect as most infotainment applications in cars are implemented on expensive multilayer boards.

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