Active antenna driver for car infotainment systems

June 12, 2014 // By Bernd Stein, Infineon
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.

AM/FM, DAB and satellite signals are received by active antenna systems with stubby, shark fin or windshield antennas. As car infotainment units have becoming more complex, the number of active antenna systems has grown as well. Sensitive circuitry like LNAs in these active antenna systems requires a stable power supply, protection and isolation from the harsh automotive environment as well as monitoring and diagnostic functions to provide antenna status. The new TLF4277-2 (figure 1) is designed to reliable supply active antennas in car infotainment applications.

Fig. 1: TLE4277-2 - second generation of single-chip ICs for active antenna supply with integrated precise current monitoring and enhanced protection features

An active antenna is an antenna that contains active electronic components. This allows - different to passive antennas - the construction of antennas of limited size and/or wide frequency range. Power for the active components may be supplied by batteries, a filtered power supply, or through the signal feeder itself (phantom power). The TLF4277-2 low drop out voltage regulator provides the related voltage to the active antenna. The adjustable output voltage (5 V to 12 V) makes the new voltage regulator capable of supplying the majority of standard active antennas, such as FM/AM, DAB, XM or SIRIUS.

The TLF4277-2 protects both the antenna and itself in this demanding electrical environment, while providing a stable output voltage. The IC also protects active antenna supply circuitry in the event of a short circuit within the antenna supply itself with an adjustable current limitation. Thermal conditions in automotive environments are equally challenging, requiring the supply to be stable over the automotive temperature range of -40 to 150°C with robust over temperature protection. In addition to these protection requirements, the TLF4277-2 simplifies the gathering of diagnostic information required to report antenna status.

New generation with enhanced features

The TLE4277-2 is the second generation of the TLE4277 family which was successfully implemented in various active antenna applications and

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