WM8733 Datasheet, PDF (9/11 Pages) Wolfson Microelectronics plc – 102dB Stereo DAC

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SYSTEM CLOCK
WM8733
The system clock is used to operate the digital filters and the noise shaping circuits. The system
clock input is at pin 14 (SCKI). The frequency of WM8733’s system clock should be set to 256fs or
384fs or 512fs, (where fs is the audio sampling frequency). The sample rate is typically: 32 kHz, 44.1
kHz, 48 kHz or 96kHz.
WM8733 has a system clock detection circuit that automatically determines whether the system
clock being supplied is at 256fs or 384fs or 512fs. The system clock should be synchronised with
LRCIN, but WM8733 is tolerant of phase differences. Severe distortion in the phase difference
between LRCIN and the system clock will be detected, and cause the device to automatically
resynchronise. During resynchronisation, the output of the device will either repeat the previous
sample, or drop the next sample, depending on the nature of the phase slip. This will ensure minimal
“click“ at the analog outputs during resynchronisation.
t_SCKIH
SCKI
t_SCKIL
Figure 5 System Clock Timing Requirements
SAMPLING RATE
(LRCIN)
32 kHz
SYSTEM CLOCK FREQUENCY (MHz)
256fs
384fs
512fs
8.192
12.288
16.384
44.1 kHz
48 kHz
96kHz
11.2896
12.288
24.576
16.9340
18.432
36.864
22.5792
24.576
49.152
Table 5 System Clock Frequencies Versus Sampling Rate
LRCIN
t_BCH
t_BCL
t_LB
BCKIN
t_BL
t_BCY
DIN
t_DS
t_DH
Figure 6 Audio Data Input Timing
WOLFSON MICROELECTRONICS LTD
PP Rev 1.3 July 2000
9