WM8955BL Wolfson Microelectronics, WM8955BL Datasheet - Page 31

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

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Production Data
AUDIO SAMPLE RATES
The WM8955BL supports a wide range of master clock frequencies and can generate many
commonly used audio sample rates directly from the master clock.
There are two clocking modes:
•
•
Table 22 Clocking and Sample Rate Control
Note:
1.
The clocking of the WM8955BL is controlled using the MCLKDIV2, USB, and SR control bits. Setting
the MCLKDIV2 bit divides MCLK by two internally. The USB bit selects between ‘Normal’ and USB
mode. Each combination of the SR4 to SR0 control bits selects one MCLK division ratio and hence
one sample rate (see Table 23). The digital filter characteristics are automatically adjusted to suit the
MCLK and sample rate selected (see Digital Filter Characteristics).
Since all sample rates are generated by dividing MCLK, their accuracy depends on the accuracy of
MCLK. If MCLK changes, the sample rates change proportionately. Note that some sample rates (e.g.
44.1kHz in USB mode) are approximated, i.e. they differ from their target value by a very small
amount. This is not audible, as the maximum deviation is only 0.27% (8.0214kHz instead of 8kHz in
USB mode – for comparison, a half-tone step corresponds to a 5.9% change in pitch).
R8 (08h)
Sample Rates
REGISTER
ADDRESS
With BCLKDIV2=1, the LRCLK output produces a non-50:50 duty cycle if BCLK/LRCLK is not an
even integer.
‘Normal’ mode supports master clocks of 128f
USB mode supports 12MHz or 24MHz master clocks. This mode is intended for use in
systems with a USB interface, and can run without a PLL.
0
5:1
6
7
BIT
USB
SR [4:0]
MCLK DIV2
BCLKDIV2
LABEL
0
00000
0
0
DEFAULT
s
, 192f
s
, 256f
Clocking Mode Select
1: USB Mode
0: ‘Normal’ Mode
Sample Rate Control
MCLK Divide by 2
0: Divide disabled
1: Divide enabled
Divide BITCLK output by 2
(use only in USB master mode, i.e.
when USB=1, MS=1)
1 = BCLK is divided by 2 (Note 1)
0 = BCLK is not divided
s
, 384f
s
, and their multiples
DESCRIPTION
PD Rev 4.1 February 2007
WM8955BL
31