Datasheet

TAS5548
SLES270 –NOVEMBER 2012 www.ti.com
D1 Sets number of speakers in the system, including possible line outputs
D3–D1 must be configured for the audio system in the application, as shown in Table 5-6.
Table 5-6. Audio System Configuration (General Control Register 0xE0)
Audio System D31–D4 D3 D2 D1 D0
6 channels or 5.1 not using PSVC 0 0 0 1 X
6 channels using PSVC 0 0 1 1 X
5.1 system using PSVC 0 0 1 1 X
8 channels or 7.1 not using PSVC (default) 0 0 0 0 X
8 channels using PSVC 0 0 1 0 X
7.1 system using PSVC 0 0 1 0 X
5.3.3.1 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 and the loudness function have no effect
on the signal.
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 is recommended:
• 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 a downmix is desired on channels 5 and 6 as lineout, the downmixing 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.
5.3.4 Recovery from Clock Error
The TAS5548 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.
5.3.5 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 is always controlled by the PSVC. When using PSVC the subwoofer cannot be
used as lineout.
5.3.6 Volume and Mute Update Rate
The TAS5548 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/f
S
seconds.
• In double speed, the update is 1 step every 8/f
S
seconds.
• In quad speed, the update is 1 step every 16/f
S
seconds.
Because of processor loading, the update rate can increase for some increments by one step every 1/f
S
to
3/f
S
. However, the variance of the total time to go from 18 dB to mute is less than 25%.
42 TAS5548 Controls and Status Copyright © 2012, Texas Instruments Incorporated
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