WM8956CGEFLSLASHV datasheet(53/80 Pages) WOLFSON

53 / 80 page

Production Data

WM8956

PD, November 2011, Rev 4.1

OTHER SAMPLE RATE CONTROL BITS

The de-emphasis filter and 3D stereo enhance functions all need to be configured for the chosen

sample rate when in use, as show in Table 34.

DEEMPH, 3DUC and 3DUC should be configured to match the chosen DAC sample rate.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R5 (05h)

DAC Control (1)

2:1

DEEMPH

[1:0]

De-Emphasis Control

11 = 48kHz sample rate

10 = 44.1kHz sample rate

01 = 32kHz sample rate

00 = No de-emphasis

R16 (10h)

3D Enhance

3DUC

Upper Cut-Off Frequency

0 = High (Recommended for

fs>=32kHz)

1 = Low (Recommended for

fs<32kHz)

3DLC

Lower Cut-Off Frequency

0 = Low (Recommended for

fs>=32kHz)

1 = High (Recommended for

fs<32kHz)

Table 34 Additional Sample Rate Controls

PLL

The integrated PLL can be used to generate SYSCLK for the WM8956 or provide clocking for external

devices via the GPIO1 pin.

The PLL is enabled by the PLLEN register bit.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R26 (1Ah)

Power

management (2)

PLLEN

PLL Enable

0 = PLL off

1 = PLL on

R52 (34h)

PLL (1)

SDM

Enable Integer Mode

0 = Integer mode

1 = Fractional mode

Table 35 PLLEN Control Bit

The PLL frequency ratio R = f2/f1 (See Figure 34) can be set using the register bits PLLK and PLLN:

PLLN = int R

PLLK = int (2

24 (R-PLLN))

EXAMPLE:

MCLK=12MHz, required clock = 12.288MHz.

R should be chosen to ensure 5 < PLLN < 13. There is a fixed divide by 4 in the PLL and a selectable

divide by N after the PLL which should be set to divide by 2 to meet this requirement.

Enabling the divide by 2 sets the required f2 = 4 x 2 x 12.288MHz = 98.304MHz.

R = 98.304 / 12 = 8.192

PLLN = int R = 8

k = int ( 2

24 x (8.192 – 8)) = 3221225 = 3126E9h

WM8956CGEFL/V Datasheet(PDF) 53 Page - Wolfson Microelectronics plc

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