WM8351CGEB/RV WOLFSON [Wolfson Microelectronics plc], WM8351CGEB/RV Datasheet - Page 45

• Manufacturer Part Number: WM8351CGEB/RV
• Manufacturer: WOLFSON [Wolfson Microelectronics plc]

Production Data
12 CLOCKING, TIMING AND SAMPLE RATES
12.1 GENERAL DESCRIPTION
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The WM8351 includes clocking circuitry for the on-chip audio CODEC, the DC-DC converters and the
auxiliary ADC. It provides the following capabilities:
The WM8351 has two internal clock generators: a 2MHz RC oscillator and a 32kHz crystal oscillator.
Clocks are required for system start-up and also for the DC-DC converter clocks; these are derived
from the internal 2MHz RC oscillator. The 32kHz crystal oscillator (or external 32kHz source) is used
to drive the internal Real Time Clock (RTC), and may also be used as a reference source for the
CODEC clock generators.
The CODEC clocks may be derived either directly from MCLK, or else via an on-chip Frequency
Locked Loop (FLL) to generate the required clocking from a wide range of reference inputs. The FLL
can take as input the external MCLK, or ADCLRCLK / DACLRCLK (in Slave modes), or the 32kHz
crystal oscillator (or external 32kHz source), and generates (typically) a 12.288MHz clock for the
CODEC.
The flexible clocking arrangements are illustrated in Figure 33.
Figure 33 Clock Generation and Distribution Scheme
32kHz (GPIOn)
32kHz (GPIOn)
ADCLRCLK
DACLRCLK
X1
X2
MCLK
f
XTAL
OSC_USER_TRIM,
OSC
= 32.768kHz
Internal RC
Oscillator
R217[3:0]
DC-DC Clock
PMU Core
FLL_CLK_SRC
R45[1:0]
RTC_CLKSRC
R218[13]
÷ 2
To RTC
FLL
2MHz F
1MHz F
ADC Clock
DAC Clock
DC-DC
DC-DC
DC-DC2
DC-DC1, 3, 4
MCLK_SEL
R40[11]
ADC_CLKDIV
R68[2:0]
DAC_CLKDIV
R54[2:0]
PD, April 2012, Rev 4.5
MCLK_DIV,
R40[10:8]
12MHz Clock
÷ N
÷ N
÷ 2
to CODEC
(256fs)
WM8351
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