CS4222 Datasheet, PDF (11/26 Pages) Cirrus Logic – 20-Bit Stereo Audio Codec with Volume Control

CS4222
Figure 4.
Analog/Digital Volume Control - Control Port
Mode Only
The DAC outputs are each routed through an at-
tenuator which is adjustable in 0.5 dB steps.
Output attenuation is available through the Out-
put Attenuator Data Bytes (#3 & #4). Level
changes are implemented with an analog volume
control until the residual output noise is equal to
the noise floor in the mute state at which point
volume changes are performed digitally. This
technique is superior to purely digital volume
control techniques as the noise is attenuated by
the same amount as the signal, thus preserving
dynamic range (see Figure 5).
The CS4222 implements a "soft" volume control
whereby level changes are achieved by ramping
DS236PP3
0 ^{Analog Digital}
Signal
Noise
0 _{Attenuation (dB)} -113.5
Figure 5. Hybrid Analog/Digital Attenuation
from the current level to the new level in 0.5 dB
steps. The default rate of volume change is 8
LRCK cycles for each 0.5 dB step (equivalent to
647 µs at Fs = 48 kHz). The rate of volume
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