WM8955BL Wolfson Microelectronics, WM8955BL Datasheet - Page 38

• Manufacturer Part Number: WM8955BL
• Description: Stereo DAC
• Manufacturer: Wolfson Microelectronics

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WM8955BL
DIGITAL FILTER CHARACTERISTICS
Table 30 Digital Filter Characteristics
Table 31 DAC Filters
TERMINOLOGY
Stop Band Attenuation (dB) – the degree to which the frequency spectrum is attenuated (outside audio band)
Pass-band Ripple – any variation of the frequency response in the pass-band region
DAC FILTER RESPONSES
Figure 20 DAC Filter Frequency Response – Type 0
DAC Filter Type 0 (USB mode, 250fs operation)
DAC Filter Type 1 (USB mode, 272fs or Normal mode operation)
Passband
Passband Ripple
Stopband
Stopband Attenuation
Passband
Passband Ripple
Stopband
Stopband Attenuation
-100
-20
-40
-60
-80
3 (256/272, 88.2/96k mode)
0
0
2 (250 USB, 96k mode)
PARAMETER
0 (250 USB)
1 (256/272)
0.5
MODE
1
Frequency (Fs)
1.5
Depending on the MCLK frequency and sample rate selected, 4 different types of digital filter can be
used in the DAC, called Type 0, 1, 2 and 3 (see “Master Clock and Audio Sample Rates”). The
performance of Types 0 and 1 is listed in the table below, the responses of all filters is shown in the
following pages.
2
TEST CONDITIONS
2.5
f > 0.5465fs
+/- 0.03dB
f > 0.584fs
+/- 0.03dB
GROUP DELAY
-6dB
-6dB
3
11/FS
16/FS
4/FS
3/FS
Figure 21 DAC Filter Ripple – Type 0
-0.01
-0.02
-0.03
-0.04
-0.05
-0.06
0.02
0.01
0
0
0.5465fs
0.05
0.584fs
MIN
-50
-50
0
0
0.1
0.15
0.2
0.5fs
0.5fs
Frequency (Fs)
TYP
0.25
0.3
0.4535fs
+/- 0.03
PD Rev 4.1 February 2007
0.416fs
+/-0.03
0.35
MAX
0.4
0.45
Production Data
0.5
UNIT
dB
dB
dB
dB
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