Datasheet

7
Biquads
in
Series
Bass
and
Treble
DRC
Bass and Treble
Bypass
Bass
and
Treble
Inline
Pre-
Volume
Post-
Volume
DRC
Bypass
DRC
Inline
B0016-02
From Input Mixer To Output Mixer
Loudness
Channel Volume
Master
Volume
Max
Volume
TAS5508C
SLES257–SEPTEMBER 2010 www.ti.com
All of the TAS5508C default values for DRC can be used except for the DRC1 decay and DRC2 decay.
Table 2-8 shows the recommended time constants and their hex values. If the user wants to implement
other DRC functions, Texas Instruments recommends using the automatic loudspeaker equalization (ALE)
tool available from Texas Instruments. The ALE tool allows the user to select the DRC transfer function
graphically. It then outputs the TAS5508C hex coefficients for download to the TAS5508C.
Table 2-8. DRC Recommended Changes From TAS5508C Defaults
I
2
C RECOMMENDED TIME RECOMMENDED
REGISTER FIELDS DEFAULT HEX
SUBADDRESS CONSTANT (ms) HEX VALUE
0x98 DRC1 energy 5 0000 883F 0000 883F
DRC1 (1 – energy) 007F 77C0 007F 77C0
0x9C DRC1 attack 5 0000 883F 0000 883F
DRC1 (1 – attack) 007F 77C0 007F 77C0
DRC1 decay 2 0001 538F 0000 00AE
DRC1 (1 – decay) 007E AC70 007F FF51
0x9D DRC2 energy 5 0000 883F 0000 883F
DRC2 (1 – energy) 007F 77C0 007F 77C0
0xA1 DRC2 attack 5 0000 883F 0000 883F
DRC2 (1 – attack) 007F 77C0 007F 77C0
DRC2 decay 2 0001 538F 0000 00AE
DRC2 (1 – decay) 007E AC70 007F FF51
Recommended DRC set-up flow if the defaults are used:
• After power up, load the recommended hex value for DRC1 and DRC2 decay and (1 – decay). See
Table 2-8.
• Enable either the pre-volume or post-volume DRC.
Recommended DRC set-up flow if the DRC design uses values different from the defaults:
• After power up, load all DRC coefficients per the DRC design.
• Enable either the pre-volume or post-volume DRC.
Figure 2-16 shows the positioning of the DRC block in the TAS5508C processing flow. As seen, the DRC
input can come either before or after soft volume control and loudness processing.
Figure 2-16. DRC Positioning in TAS5508C Processing Flow
Figure 2-17 illustrates a typical DRC transfer function.
34 Description Copyright © 2010, Texas Instruments Incorporated
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