BCM43455 Preliminary Data Sheet
Bluetooth Power Management Unit
BBC Power Management
The following are low-power operations for the BBC:
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Physical layer packet-handling turns the RF on and off dynamically within transmit/receive packets.
Bluetooth-specified low-power connection modes: sniff, hold, and park. While in these modes, the
BCM43455 runs on the low-power oscillator and wakes up after a predefined time period.
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A low-power shutdown feature allows the device to be turned off while the host and any other devices in the
system remain operational. When the BCM43455 is not needed in the system, the RF and core supplies
are shut down while the I/O remains powered. This allows the BCM43455 to effectively be off while keeping
the I/O pins powered so they do not draw extra current from any other devices connected to the I/O.
During the low-power shutdown state, provided VDDIO remains applied to the BCM43455, all outputs are
tristated, and most input signals are disabled. Input voltages must remain within the limits defined for normal
operation. This is done to prevent current paths or create loading on any digital signals in the system and
enables the BCM43455 to be fully integrated in an embedded device to take full advantage of the lowest
power-saving modes.
Two BCM43455 input signals are designed to be high-impedance inputs that do not load the driving signal
even if the chip does not have VDDIO power supplied to it: the frequency reference input (WRF_TCXO_IN)
and the 32.768 kHz input (LPO). When the BCM43455 is powered on from this state, it is the same as a
normal power-up, and the device does not contain any information about its state from the time before it was
powered down.
Wideband Speech
®
The BCM43455 provides support for wideband speech (WBS) using on-chip Broadcom SmartAudio
technology. The BCM43455 can perform subband-codec (SBC), as well as mSBC, encoding and decoding of
linear 16 bits at 16 kHz (256 Kbps rate) transferred over the PCM bus.
Packet Loss Concealment
Packet Loss Concealment (PLC) improves apparent audio quality for systems with marginal link performance.
Bluetooth messages are sent in packets. When a packet is lost, it creates a gap in the received audio bit-stream.
Packet loss can be mitigated in several ways:
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Fill in zeros.
Ramp down the output audio signal toward zero (this is the method used in current Bluetooth headsets).
Repeat the last frame (or packet) of the received bit-stream and decode it as usual (frame repeat).
These techniques cause distortion and popping in the audio stream. The BCM43455 uses a proprietary
waveform extension algorithm to provide dramatic improvement in the audio quality. Figure 8 and Figure 9 on
page 44 show audio waveforms with and without Packet Loss Concealment. Broadcom PLC/BEC algorithms
also support wideband speech.
Broadcom®
November 5, 2015 • 43455-DS109-R
Page 43
BROADCOM CONFIDENTIAL
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