WM8803CDTSLASHV datasheet(12/45 Pages) WOLFSON

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WM8803

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PP Rev 1.1 September 2003

OSCILLATOR AMPLIFIER (XIN AND XOUT)

The following methods can be used to supply a clock signal to the internal oscillator amplifier.

(a) Oscillator element

CLKOUT

XIN

XOUT

(b) External clock signal

CLKOUT

XIN

XOUT

CLKOUT

XIN

XOUT

Figure 5 XIN and XOUT Circuit Structures

If an oscillator element is used, it is recommended that it provides the desired system operating

frequency as its fundamental frequency. Since the load capacitance depends on the oscillator

element characteristics, the circuit must be designed for the crystal used.

In normal operation, the clock signal to the XIN pin should be supplied at all times.

An externally supplied clock is used when the PLL circuit is unlocked and when XIN is the clock

source. A clock source input to XIN is also required when calculating the input data sampling

frequency.

A clock of frequency 11.2896, 12.288, 16.9344, 22.5792, 24.576, or 33.8688MHz that matches the

setting of the XISEL[2:0] should be applied. Digital data should only be input after the XISEL[2:0] has

been set to match the oscillator or external clock input frequency. The WM8803 may malfunction if

data is input when the input frequency and XISEL[2:0] frequency do not match.

The WM8803 will operate even when the frequency set with the XISEL[2:0] and the frequency

supplied to XIN differ. However, maintenance of continuity of clock switching and the input fs

calculation are not guaranteed.

The WM8803 supports an application in which CLKOUT is connected to XIN and XISEL3 is set, thus

requiring no oscillator element. However, since only the VCO is used as the source clock, when the

PLL is not in the locked state the VCO free-running frequency (10M to 16MHz) will be output from

CLKOUT. Furthermore, input fs calculation and limitation are not possible with this technique.

Additionally, since no clock is supplied to the oscillator amplifier circuit when the VCO is set to the

stopped state, the whole system will go to the stopped state. This function limits settings to

PLLCK[1:0] = “00”.

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