STA323W ST Microelectronics, STA323W Datasheet - Page 22

• Manufacturer Part Number: STA323W
• Description: 2.1 High Efficiency Digital Audio System
• Manufacturer: ST Microelectronics

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STA323W
7.8.2.2Channel 2 Volume (Address 09h)
7.8.2.3Channel 3 Volume (Address 0Ah)
7.8.3 Volume Description
The volume structure of the STA323W consists of individual volume registers for each of the three chan-
nels and a master volume register, and individual channel volume trim registers. The channel volume set-
tings are normally used to set the maximum allowable digital gain and to hard-set gain differences
between certain channels. These values are normally set at the initialization of the IC and not changed.
The individual channel volumes are adjustable in 0.5dB steps from +48dB to -80 dB. The master volume
control is normally mapped to the master volume of the system. The values of these two settings are
summed to find the actual gain/volume value for any given channel.
When set to 1, the Master Mute will mute all channels, whereas the individual channel mutes (CxM) will
mute only that channel. Both the Master Mute and the Channel Mutes provide a “soft mute” with the vol-
ume ramping down to mute in 4096 samples from the maximum volume setting at the internal processing
rate (~96kHz). A “hard mute” can be obtained by commanding a value of all 1’s (FFh) to any channel vol-
ume register or the master volume register. When volume offsets are provided via the master volume reg-
ister any channel whose total volume is less than –100dB will be muted.
All changes in volume take place at zero-crossings when ZCE = 1 (configuration register E) on a per chan-
nel basis as this creates the smoothest possible volume transitions. When ZCE=0, volume updates will
occur immediately.
The STA323W also features a soft-volume update function that will ramp the volume between intermedi-
ate values when the value is updated, when SVE = 1 (configuration register E). This feature can be dis-
abled by setting SVE = 0.
Each channel also contains an individual channel volume bypass. If a particular channel has volume by-
passed via the CxVBP = 1 register then only the channel volume setting for that particular channel affects
the volume setting, the master volume setting will not affect that channel. Also, master soft-mute will not
affect the channel if CxVBP = 1.
Each channel also contains a channel mute. If CxM = 1 a soft mute is performed on that channel
Table 16. Master Volume Offset as a function of MV (7..0).
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C2V7
C3V7
4
D7
D7
0
0
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01001100 (4Ch)
11111110 (FEh)
11111111 (FFh)
00000000 (00h)
00000001 (01h)
00000010 (02h)
MV (7..0)
…
…
C2V6
C3V6
D6
D6
1
1
C2V5
C3V5
D5
D5
1
1
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C2V4
C3V4
D4
D4
0
0
Volume Offset from Channel Value
C2V3
C3V3
D3
D3
0
0
Hard Master Mute
-127dB
-0.5dB
-38dB
-1dB
0dB
…
…
C2V2
C3V2
D2
D2
0
0
C2V1
C3V1
D1
D1
0
0
C2V0
C3V0
D0
D0
0
0
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