TLV320AIC3204 Datasheet, PDF (48/159 Pages) Texas Instruments – Ultra Low Power Stereo Audio Codec

TLV320AIC3204
Ultra Low Power Stereo Audio Codec
SLOS602A – SEPTEMBER 2008 – REVISED OCTOBER 2008
5.8.2.8 5 Biquads, 1^st order IIR, AGC, Filter C
From Delta-Sigma
Modulator or
Digital Microphone
Filter C
HA
HB
HC
HD
HE
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1st Order
´
IIR
AGC
Gain
Compen
sation
To Audio
Interface
AGC
From
Digital Vol. Ctrl
To Analog PGA
Figure 5-11. Signal Chain for PRB_R14 and PRB_R17
5.8.2.9 25 Tap FIR, 1^st order IIR, AGC, Filter C
From Delta-Sigma
Modulator or
Digital Microphone
Filter C
25-Tap FIR
1^st Order
´
IIR
AGC
Gain
Compen
sation
To Audio
Interface
AGC
From
Digital Vol. Ctrl
To Analog PGA
Figure 5-12. Signal for PRB_R15 and PRB_R18
5.8.3 User Programmable Filters
Depending on the selected processing block, different types and orders of digital filtering are available. A
1st-order IIR filter is always available, and is useful to efficiently filter out possible DC components of the
signal. Up to 5 biquad section or alternatively up to 25-tap FIR filters are available for specific processing
blocks. The coefficients of the available filters are arranged as sequentially indexed coefficients in two
banks. If adaptive filtering is chosen, the coefficient banks can be switched on-the-fly. For more details on
adaptive filtering see Section 5.9.7 below.
The coefficients of these filters are each 24-bits wide, in two's-complement and occupy 3 consecutive 8-bit
registers in the register space. For default values please see .
5.8.3.1 1^st Order IIR Section
The transfer function for the first order IIR Filter is give by [equation not in source]
H(z)
=
N₀
2 ²³
+ N₁z ^-1
- D₁z ^-1
(5-2)
The frequency response for the 1^st order IIR Section with default coefficients is flat at a gain of 0dB.
Filter
1^st Order
IIR
Table 5-5. ADC 1st order IIR Filter Coefficients
FIlter
Coefficient
N0
N1
D1
ADC Coefficient Left
Channel
C4 (Pg 8,Reg 24,25,26)
C5 (Pg 8,Reg 28,29,30)
C6 (Pg 8,Reg 32,33,34)
ADC Coefficient Right Channel
C36 (Pg 9,Reg 32,33,34)
C37 (Pg 9,Reg 36,37,38)
C39 (Pg 9,Reg 40,41,42)
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Application Information
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