TAS5508 datasheet(49/105 Pages) TI

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3.3.3.1 Using Line Outputs in 6-Channel Configurations

3.3.4

Recovery from Clock Error

3.3.5

Power-Supply Volume-Control Enable

3.3.6

Volume and Mute Update Rate

TAS5508

8-Channel Digital Audio PWM Processor

www.ti.com

SLES091D – FEBRUARY 2004 – REVISED JULY 2009

Table 3-7. Audio System Configuration (General Control Register 0xE0)

Audio System

D31–D4

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

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.

The TAS5508 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 I2C system control register 0x03.

The power-supply volume control (PSVC) can be enabled and disabled via I2C 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.

The TAS5508 has fixed soft volume and mute ramp durations. The ramps are linear. The soft volume and

mute ramp rates are adjustable by programming the I2C 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%.

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