WM8721_04 Datasheet, PDF (24/37 Pages) Wolfson Microelectronics plc – Internet Audio DAC with Integrated Headphone Driver

WM8721 / WM8721L
USB MODE SAMPLE RATES
In USB mode the MCLK input is 12MHz only.
SAMPLING
RATE
DAC
kHz
48
MCLK
FREQUENCY
MHz
12.000
BOSR
0
SAMPLE
RATE
REGISTER SETTINGS
SR3 SR2 SR1
0
0
0
Production Data
DIGITAL
FILTER
TYPE
SR0
0
0
44.1 (Note 2)
12.000
1
1
0
0
0
1
8
12.000
0
0
0
0
1
0
8 (Note 1)
12.000
1
1
0
0
1
1
32
12.000
0
0
1
1
0
0
96
12.000
0
0
1
1
1
3
88.2 (Note 3)
12.000
1
1
1
1
1
2
Table 13 USB Mode Sample Rate Look-up Table
Notes:
1. 8k not exact, actual = 8.021kHz
2. 44.1k not exact, actual = 44.118kHz
3. 88.1k not exact, actual = 88.235kHz
4. All other combinations of BOSR and SR[3:0] that are not in the truth table are invalid
The BOSR bit represents the base over-sampling rate. This is the rate that the WM8721 digital signal
processing is carried out at and the sampling rate will always be a sub-multiple of this. In USB mode,
with BOSR = 0, the base over-sampling rate is defined at 250fs, with BOSR = 1, the base over-
sampling rate is defined at 272fs. This can be used to determine the actual audio sampling rate
required by the DAC.
The exact sample rates supported for all combinations are defined by the relationships in Table 14
below.
TARGET
SAMPLING
RATE
kHz
8
ACTUAL SAMPLING RATE
BOSR=0
BOSR=1
( 250fs)
(272fs)
kHz
kHz
8
8.021
12MHz/(250 x 48/8)
12MHz/(272 x 11/2)
32
32
not available
44.1
12MHz/(250 x 48/32)
not available
44.118
12MHz/272
48
48
not available
88.2
12MHz/250
not available
88.235
12MHz/136
96
96
not available
12MHz/125
Table 14 USB Mode Actual Sample Rates
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PD Rev 4.0 November 2004
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