CYW4343X
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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 CYW4343X is not needed in the system, the RF and core supplies are shut down while the I/O
remains powered. This allows the CYW4343X to effectively be off while keeping the I/O pins powered, so they do not draw
extra current from any other I/O-connected devices.
During the low-power shut-down state, provided VDDIO remains applied to the CYW4343X, 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 digital signals in the system and enables the CYW4343X to be fully integrated in an embedded device to take
full advantage of the lowest power-saving modes.
Two CYW4343X 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
CYW4343X 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.
8.5.1 FM Power Management
The CYW4343X FM subsystem can operate independently of, or in tandem with, the Bluetooth RF and BBC subsystems. The FM
subsystem power management scheme operates in conjunction with the Bluetooth RF and BBC subsystems. The FM block does
not have a low power state, it is either on or off.
8.5.2 Wideband Speech
The CYW4343X provides support for wideband speech (WBS) technology. The CYW4343X 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.
8.6 Packet Loss Concealment
Packet Loss Concealment (PLC) improves the apparent audio quality for systems with marginal link performance. Bluetooth mes-
sages 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 CYW4343X uses a proprietary waveform extension algo-
rithm to provide dramatic improvement in the audio quality. Figure 30 and Figure 31 show audio waveforms with and without Packet
Loss Concealment. Cypress PLC/BEC algorithms also support wideband speech.
Figure 30. CVSD Decoder Output Waveform Without PLC
Packet losses causes ramp-down
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