wm8953 Wolfson Microelectronics plc, wm8953 Datasheet - Page 69

• Manufacturer Part Number: wm8953
• Description: Low Power Stereo Adc With Pll And Tdm Interface Low Power Stereo Adc With Pll And Tdm Interface
• Manufacturer: Wolfson Microelectronics plc

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Production Data
ADC SAMPLE RATE
The ADC sample rate is selectable, relative to SYSCLK, by setting the register fields ADC_CLKDIV.
This must be set according to the SYSCLK frequency, and according to the selected clocking mode.
Two clocking modes are provided - Normal Mode (AIF_LRCLKRATE = 0) allows selection of the
commonly used sample rates from typical audio system clocking frequencies (eg. 12.288MHz); USB
Mode (AIF_LRCLKRATE = 1) allows many of these sample rates to be generated from a 12MHz
USB clock. Depending on the available clock sources, the USB mode may be used to save power by
supporting 44.1kHz operation without requiring the PLL.
The AIF_LRCLKRATE field must be set as described in Table 39 to ensure correct operation of
internal functions according to the SYSCLK / Fs ratio. Table 40 describes the available sample rates
using four different common MCLK frequencies.
In Normal mode, the programmable division set by ADC_CLKDIV must ensure that a 256 * ADC Fs
clock is generated for the ADC DSP.
In USB mode, the programmable division set by ADC_CLKDIV must ensure that a 272 * ADC Fs
clock is generated for the ADC DSP.
Note that in USB mode, the ADC sample rates do not match exactly with the commonly used sample
rates (e.g. 44.118 kHz instead of 44.100 kHz). At most, the difference is less than 0.5%. Data
recorded at 44.100 kHz sample rate and replayed at 44.118 kHz will experience a slight (sub 0.5%)
pitch shift as a result of this difference. Note also that the USB mode cannot be used to generate a
48kHz samples rate from a 12MHz MCLK; the PLL should be used in this case.
Table 39 ADC Sample Rate Control
R7 (07h)
R10 (0Ah)
REGISTER
ADDRESS
7:5
10
BIT
ADC_CLKDIV
[2:0]
AIF_LRCLKRAT
E
LABEL
DEFAULT
000b
0b
ADC Sample Rate Divider
000 = SYSCLK / 1.0
001 = SYSCLK / 1.5
010 = SYSCLK / 2.0
011 = SYSCLK / 3.0
100 = SYSCLK / 4.0
101 = SYSCLK / 5.5
110 = SYSCLK / 6.0
111= Reserved
LRCLK Rate
0 = Normal mode (256 * fs)
1 = USB mode (272 * fs)
DESCRIPTION
PD, January 2009, Rev 4.0
WM8953
69