BCM4339 Preliminary Data Sheet
Audio Features
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Soft Mute—Improves the user experience by dynamically muting the output audio proportionate to the FM
signal C/N. This prevents the user from being assaulted with a blast of static. The mute characteristic is
fully programmable to accommodate fine tuning of the output signal level. An example mute characteristic
is shown in Figure 23.
Figure 23: Example Soft Mute Characteristic
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High Cut—A programmable high-cut filter is provided to reduce the amount of high-frequency noise
caused by static in the output audio signal. Like the soft mute circuit, it is fully programmable to allow for
any amount of high cut based on the FM signal C/N.
Audio Pause Detect—The FM receiver monitors the magnitude of the audio signal and notifies the host
through an interrupt when the magnitude of the signal has fallen below the threshold set for a
programmable period. This feature can be used to provide alternate frequency jumps during periods of
silence to minimize disturbances to the listener. Filtering techniques are used within the audio pause
detection block to provide more robust presence-to-silence detection and silence-to-presence detection.
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Automatic Antenna Tuning—The BCM4339 has an on-chip automatic antenna tuning network. When used
with a single off-chip inductor, the on-chip circuitry automatically chooses an optimal on-chip matching
component to obtain the highest signal strength for the desired frequency. The high-Q nature of this
matching network simultaneously provides out-of-band blocking protection as well as a reduction of
radiated spurious emissions from the FM antenna. It is designed to accommodate a wide range of external
wire antennas.
Broadcom®
November 17, 2014 • 4339-DS106-R
Page 68
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