TAS5705
SLOS549–JUNE 2008...................................................................................................................................................................................................... www.ti.com
The Bass Management function is explained in Figure 48.
A
Lf (Ch 1)
B
Rf (Ch 2)
C
Ls (Ch 3)
D
Rs (Ch 4)
F
Sub (Ch 6)
Bass Management Output
+
10 dB
Bass Management Output = BS_Out (linear) = Ch 6 = F ´ 3.121 + (A + B + C + D)
BS_Out (log) = 20 ´ log (BS_Out)
B0291-01
NOTE: Selection of A, B, C, D, or F is determined by the input multiplexer selection register (0x20).
Figure 48. Bass Management Block Diagram
Downmix is defined by I2C register 0x21, bits (3:0), as listed in Table 5.
Table 5. Downmix Definitions
Bits 3:0
X0X0
X0X1
X1X0
X1X1
0X0X
0X1X
1X0X
1X1X
Definition
L' = (0.000 × Ls + 0.000 × L) / 1.000
L' = (0.000 × Ls + 1.000 × L) / 1.000
L' = (1.000 × Ls + 0.000 × L) / 1.000
L' = (0.707 × Ls + 1.000 × L) / 1.707
R' = (0.000 × Rs + 0.000 × R) / 1.000
R' = (0.000 × Rs + 1.000 ×R) / 1.000
R' = (1.000 × Rs + 0.000 × R) / 1.000
R' = (0.707 × Rs + 1.000 × R) / 1.707
BANK SWITCHING
The TAS5705 uses an approach called bank switching together with automatic sample-rate detection. All
processing features that must be changed for different sample rates are stored internally in the TAS5705. The
TAS5705 has three full banks storing information, one for 32 kHz, one for 44.1/48 kHz, and one for all other data
rates. Combined with the clock-rate autodetection feature, bank switching allows the TAS5705 to detect
automatically a change in the input sample rate and switch to the appropriate bank without any MCU
intervention.
The TAS5705 supports three banks of coefficients to be updated during the initialization. One bank is for 32 kHz,
a second bank is for 44.1/48 kHz, and a third bank is for all other sample rates. An external controller updates
the three banks (see the I2C register mapping table for bankable locations) during the initialization sequence.
If the autobank switch is enabled (register 0x50, bits 2:0) , then the TAS5705 automatically swaps the
coefficients for subsequent sample rate changes, avoiding the need for any external controller intervention for a
sample rate change.
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