WM8580AGEFTV datasheet(53/106 Pages) WOLFSON

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WM8580A

PD, Rev 4.9, November 2013

PHASE-LOCKED LOOPS AND S/PDIF CLOCKING (SOFTWARE MODE)

The WM8580A is equipped with two independent phase-locked loop clock generators and a

comprehensive clocking scheme which provides maximum flexibility and function and many

configurable routing possibilities for the user in software mode. An overview of the software mode

clocking scheme is shown in Figure 38.

PLL_A

( R = f2 / f1 )

DIV

OSCCLK

DIV

PLLACLK

OSC

CLKOUT

XOUT

XIN

S/PDIF RX

PLL_B

( R = f2 / f1 )

DIV

PLLBCLK

OSCCLK

PLLACLK

MCLK

PLLBCLK

OSCCLK

PLLACLK

CLK2

CLK1

Figure 38 PLL and Clock Select Circuit

OSCILLATOR

The function of the oscillator is to generate the OSCCLK oscillator clock signal. This signal may be

used as:



The clock source for the PLLs.



A selectable clock source for the MCLK pin, when the pin is configured as an output.



A selectable clock source for the CLKOUT pin, when enabled.

Whenever the PLLs or the S/PDIF receiver is enabled, the OSCCLK signal must be present to enable

the PLLs to generate the necessary clock signals.

The oscillator uses a Pierce type oscillator drive circuit. This circuit requires an external crystal and

appropriate external loading capacitors. The oscillator circuit contains a bias generator within the

WM8580A and hence an external bias resistor is not required. Crystal frequencies between 10 and

14.4MHz or 16.28MHz and 27MHz can be used in software mode. In this case the oscillator XOUT

must be powered up using the OSCPD bit. The recommended circuit is shown in the recommended

components diagram, please refer to Figure 55.

Alternatively, an external CMOS compatible clock signal can be applied to the XIN pin in the absence

of a crystal. This is not recommended when using the PLL as the PLL requires a jitter-free OSCCLK

signal for optimum performance. In this case the oscillator XOUT can be powered down using the

OSCPD bit.

WM8580AGEFTV Datasheet(PDF) 53 Page - Wolfson Microelectronics plc

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