0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
Frequency Normalized to f
S
Magnitude
–
dB
ADC Channel Response for Decimation Filter A
(Red line corresponds to –73 dB)
G013
Digital Microphone Input/Decimation Filter
2.3.3.1.3 Decimation Filter
The TLV320DAC3203 offers 3 different types of decimation filters. The integrated digital decimation filter
removes high-frequency content and down samples the audio data from an initial sampling rate of
AOSR*Fs to the final output sampling rate of Fs. The decimation filtering is achieved using a higher-order
CIC filter followed by linear-phase FIR filters. The decimation filter cannot be chosen by itself, it is implicitly
set through the chosen processing block.
The following subsections describe the properties of the available filters A, B and C.
2.3.3.1.3.1 Decimation Filter A
This filter is intended for use at sampling rates up to 48kHz. When configuring this filter, the oversampling
ratio of the can either be 128 or 64. For highest performance the oversampling ratio must be set to 128.
Please also see the PowerTune chapter for details on performance and power in dependency of AOSR.
Filter A can also be used for 96kHz at an AOSR of 64.
Table 2-9. Decimation Filter A, Specification
Parameter
Condition
Value (Typical)
Units
AOSR = 128
Filter Gain Pass Band
0…0.39 Fs
0.062
dB
Filter Gain Stop Band
0.55…64Fs
–73
dB
Filter Group Delay
17/Fs
Sec.
Pass Band Ripple, 8 ksps
0…0.39 Fs
0.062
dB
Pass Band Ripple, 44.1 ksps
0…0.39 Fs
0.05
dB
Pass Band Ripple, 48 ksps
0…0.39 Fs
0.05
dB
AOSR = 64
Filter Gain Pass Band
0…0.39 Fs
0.062
dB
Filter Gain Stop Band
0.55…32Fs
–73
dB
Filter Group Delay
17/Fs
Sec.
Pass Band Ripple, 8 ksps
0…0.39 Fs
0.062
dB
Pass Band Ripple, 44.1 ksps
0…0.39 Fs
0.05
dB
Pass Band Ripple, 48 ksps
0…0.39 Fs
0.05
dB
Pass Band Ripple, 96 ksps
0…20kHz
0.1
dB
Figure 2-17. Decimation Filter A, Frequency Response
30
TLV320DAC3203 Application
SLAU434 – May 2012
Copyright © 2012, Texas Instruments Incorporated