PRELIMINARY
CYW43438
■ Soft Mute—Improves the user experience by dynamically muting the output audio proportionate to the FM signal C/N. This prevents
a blast of static to the user. The mute characteristic is fully programmable to accommodate fine tuning of the output signal level. An
example mute characteristic is shown in Figure 30.
Figure 30. Soft Muting Characteristic
Input C/N (dB)
■ 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 provide 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.
■ Automatic Antenna Tuning—The CYW43438 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.
Document Number: 002-14796 Rev. *K
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