TAS5508B_17 Datasheet, PDF (33/104 Pages) Texas Instruments – 8-Channel Digital Audio PWM Processor

www.ti.com
TAS5508B
8-Channel Digital Audio PWM Processor
SLES162C – DECEMBER 2005 – REVISED JULY 2009
All of the TAS5508B 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 TAS5508B hex coefficients for download to the TAS5508B.
I²C
SUBADDRESS
0x98
0x9C
0x9D
0xA1
Table 2-8. DRC Recommended Changes From TAS5508B Defaults
REGISTER FIELDS
DRC1 energy
DRC1 (1 – energy)
DRC1 attack
DRC1 (1 – attack)
DRC1 decay
DRC1 (1 – decay)
DRC2 energy
DRC2 (1 – energy)
DRC2 attack
DRC2 (1 – attack)
DRC2 decay
DRC2 (1 – decay)
RECOMMENDED TIME
CONSTANT (ms)
5
5
2
5
5
2
RECOMMENDED
HEX VALUE
0000 883F
007F 77C0
0000 883F
007F 77C0
0001 538F
007E AC70
0000 883F
007F 77C0
0000 883F
007F 77C0
0001 538F
007E AC70
DEFAULT HEX
0000 883F
007F 77C0
0000 883F
007F 77C0
0000 00AE
007F FF51
0000 883F
007F 77C0
0000 883F
007F 77C0
0000 0056
003F FFA8
Recommended DRC setup 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 using I²C registers 0x96 and 0x97. Note that to
avoid a potential timing problem, there should be a 10-ms delay between a write to 0x96 and a write to
0x97.
Recommended DRC setup 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. Note that to avoid a potential timing problem, there
should be a 10-ms delay between a write to 0x96 and a write to 0x97.
Figure 2-16 shows the positioning of the DRC block in the TAS5508B processing flow. As seen, the DRC
input can come either before or after soft volume control and loudness processing.
Master
Volume
Channel Volume
Bass and Treble
Bypass
Max
Volume
Loudness
DRC
Bypass
From Input Mixer
7
Biquads
in
Series
Bass
and
Treble
Bass
and
Treble
Inline
Pre- Post-
Volume Volume
DRC
DRC
Inline
Figure 2-16. DRC Positioning in TAS5508B Processing Flow
To Output Mixer
B0016-02
Submit Documentation Feedback
Description
33