BCM43455 Preliminary Data Sheet
Audio Features
Audio Features
A number of features are implemented in the BCM43455 to provide the best possible audio experience for the
user.
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Mono/Stereo Blend, Switch, or FME—The BCM43455 provides automatic control of the stereo or mono
settings based on the FM signal carrier-to-noise ratio (C/N). This feature is used to maintain the best
possible audio SNR based on the FM channel condition. Three modes of operation are supported:
– Blend: In this mode, fine control of stereo separation is used to achieve optimal audio quality over a
wide range of input C/N. The amount of separation is fully programmable. In Figure 20, the separation is
programmed to maintain a minimum 50 dB SNR across the blend range.
– Extended blend: In this mode, stereo separation is maximized across a wide range of input CNR.
Broadcom static suppression typically gives a static-free user experience to within 3 dB of ultimate
sensitivity.
– Switch: In this mode, the audio switches from full stereo to full mono at a predetermined level to
maintain optimal audio quality. The stereo-to-mono switch point and the mono-to-stereo switch points
are fully programmable to provide the desired amount of audio SNR. In Figure 21 on page 63, the
switch point is programmed to switch to mono to maintain a 40 dB SNR.
– FM enhancement (FME): In this mode, advanced digital signal processing in the FM receiver greatly
enhances the stereo separation of the received audio. Traditional FM receivers deliver a full stereo
signal at a high carrier-to-noise ratio (CNR) and gradually blend into mono as the CNR drops. The
Broadcom stereo extension allows full stereo separation to within 2 dB of the FM receiver sensitivity
threshold. The same signal processing delays the onset of pops at the FM sensitivity threshold and
reduces the ambient background noise by more than 20 dB in the low CNR region near sensitivity. The
result is a low-noise full stereo signal at input RF levels lower than previously achievable.
Figure 20: Audio SNR for Blend, Switch, and FME Modes
Broadcom®
November 5, 2015 • 43455-DS109-R
Page 62
BROADCOM CONFIDENTIAL
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