TAS5504 datasheet(27/96 Pages) TI

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Introduction

SLES123 − October 2004

TAS5504

1.8.1 Auto Mute and Mute

The TAS5504 has individual channel automute controls that are enabled via the I2C interface. There are two

separate detectors used to trigger the automute:

•

Input Auto Mute: All channels are muted when all 8 inputs to the TAS5504 are less in magnitude than the

input threshold value for a programmable amount of time.

•

Output Auto Mute: A single channel is muted when the output of the DAP section is less in magnitude than

the input threshold value for a programmable amount of time.

The detection period and thresholds for these two detectors are the same.

This time interval is selectable via I2C to be from 1 ms. to 110 ms. The increments of time are 1, 2, 3, 4, 5, 10,

20, 30, 40, 50, 60, 70, 80, 90, 100, and 110 ms. This interval is independent of the sample rate. The default

value is mask programmable.

The input threshold value is an unsigned magnitude that is expressed as a bit position. This value is adjustable

via I2C. The range of the input threshold adjustment is from below the LSB (bit position 0) to below bit position

12 in a 24 bit input data word (bit positions 8 to 20 in the DSPE). This provides an input threshold that can be

adjusted for 12 to 24 bits of data. The default value is mask programmable.

31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10

23 22 21 20 19 18 17 16 15 14 13 12 11 10

DVD Data Range

CD Data Range

Threshold Range

24-Bit Input

32-Bit in DSPE

Representation

Figure 1−14. Auto Mute Threshold

The auto mute state is exited when the TAS5504 receives one sample that is greater that the output threshold.

The output threshold can be one of two values:

•

Equal to the input threshold

•

6 dB (one bit position) greater than the input threshold

The value for the output threshold is selectable via I2C. The default value is mask programmable.

The system latency enables the data value that is above the threshold to be preserved and output.

A mute command initiated by automute, master mute, individual I2C mute, the AM interference mute

sequence, or the bank switch mute sequence overrides an unmute command or a volume command. While

a mute command is activated, the commanded channels transition to the mute state. When a channel is

unmuted, it goes to the last commanded volume setting that has been received for that channel.

1.9

Loudness Compensation

The loudness compensation function compensates for the Fletcher-Munson loudness curves. The TAS5504

loudness implementation tracks the volume control setting to provide spectral compensation for weak low or

high frequency response at low volume levels. For the volume tracking function both linear and log control laws

can be implemented. Any biquad filter response can be used to provide the desired loudness curve. The

control parameters for the loudness control are programmable via the I2C interface.

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