CDB4222 Просмотр технического описания (PDF) - Cirrus Logic

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CDB4222

20-Bit Stereo Audio Codec with Volume Control

Cirrus Logic 

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

11

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