www.ti.com
SLES257 – SEPTEMBER 2010
Table 3-7. Audio System Configuration (General Control Register 0xE0)
Audio System
6 channels or 5.1 not using PSVC
6 channels using PSVC
5.1 system using PSVC
8 channels or 7.1 not using PSVC (default)
8 channels using PSVC
7.1 system using PSVC
D31–D4
0
0
0
0
0
0
D3
0
0
1
0
0
1
D2
0
1
1
0
1
1
D1
1
1
1
0
0
0
D0
X
X
X
X
X
X
3.3.3.1
Using Line Outputs in 6-Channel Configurations
The audio system can be configured for a 6-channel configuration (with 2 lineouts) by writing a 1 to bit D1
of register 0xE0 (general control register). In this configuration, channel-5 and -6 processing are exactly
the same as the other channels, except that the master volume has no effect.
Note that in 6-channel configuration, channels 5 and 6 are unaffected by back-end error (BKND_ERR
goes low).
To
•
•
•
•
•
•
use channels 5 and 6 as unprocessed lineouts, the following setup should be done:
Channel-5 volume and channel-6 volume should be set for a constant output such as 0 dB.
Bass and treble for channels 5 and 6 can be used if desired.
DRC1 should be bypassed for channels 5 and 6.
If enabled, the loudness function shapes the response of channels 5 and 6. However, the amplitude of
5 and 6 is not used in determining the loudness response.
If a down mix is desired on channels 5 and 6 as lineout, the down mixing can be performed using the
channel-5 and channel-6 input mixers.
The operation of the channel-5 and -6 biquads is unaffected by the 6-/8-channel configuration setting.
3.3.4
Recovery from Clock Error
The TAS5508C can be set either to perform a volume ramp up during the recovery sequence of a clock
error or simply to come up in the last state (or desired state if a volume or tone update was in progress).
This feature is enabled via I
2
C system control register 0x03.
3.3.5
Power-Supply Volume-Control Enable
The power-supply volume control (PSVC) can be enabled and disabled via I
2
C register 0xE0. The
subwoofer PWM output can be configured to be controlled by the PSVC or digitally attenuated when
PSVC is enabled (for powered subwoofer configurations). Note that PSVC cannot be simultaneously
enabled along with unmute outputs after clock error feature.
3.3.6
Volume and Mute Update Rate
The TAS5508C has fixed soft volume and mute ramp durations. The ramps are linear. The soft volume
and mute ramp rates are adjustable by programming the I
2
C register 0xD0 for the appropriate number of
steps to be 512, 1024, or 2048. The update is performed at a fixed rate regardless of the sample rate.
• In normal speed, the update rate is 1 step every 4/Fs seconds.
• In double speed, the update is 1 step every 8/Fs seconds.
• In quad speed, the update is 1 step every 16/Fs seconds.
Because of processor loading, the update rate can increase for some increments by 1/Fs to 3/Fs.
However, the variance of the total time to go from 18 dB to mute is less than 25%.
Copyright © 2010, Texas Instruments Incorporated
TAS5508C Controls and Status
Product Folder Link(s):
49
TI [ TEXAS INSTRUMENTS ]
