WM8959 datasheet(60/155 Pages) WOLFSON

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WM8959

Pre-Production

PP, May 2008, Rev 3.1

OUTPUT SIGNAL PATH VOLUME CONTROL

The output drivers LOPGA, ROPGA, LOUT and ROUT can be independently controlled as shown in

Table 27 and Table 28.

To minimise pop noise it is recommended that only the LOPGAVOL, ROPGAVOL, LOUTVOL and

ROUTVOL are modified while the output signal path is active. Other gain controls are provided in the

output signal path to provide appropriate relative scaling of signals from different sources, and to

prevent clipping when multiple signals are mixed. To prevent pop noise, only the gain controls noted

above should be modified while playback is active.

To prevent "zipper noise", a zero-cross function is provided on these output paths, so that when

enabled, volume updates will not take place until a zero-crossing is detected. In the event of a long

period without zero-crossings, a timeout function is available. When this function is enabled (using

the TOCLK_ENA register bit), the volume will update after the timeout period if no earlier zero-cross

has occurred. The timeout period is set by TOCLK_RATE. See “Clocking and Sample Rates” for

more information on these fields.

The OPVU bit controls the loading of the output driver volume data. When OPVU is set to 0, the

volume control data will be loaded into the respective control register, but will not actually change the

gain setting. The LOPGA, ROPGA, LOUT and ROUT volume settings are all updated when a 1 is

written to OPVU. This makes it possible to update the gain of all output paths simultaneously.

Note that the headphone outputs LOUT and ROUT have dedicated volume controls. As a result, the

output PGAs LOPGA and ROPGA do not need to be enabled to provide volume control for the LOUT

and ROUT outputs.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

OPVU[2]

N/A

Output PGA Volume Update

Writing a 1 to this bit will update

LOPGA, ROPGA, LOUTVOL and

ROUTVOL volumes simultaneously.

LOPGAZC

LOPGA Zero Cross Enable

0 = Zero cross disabled

1 = Zero cross enabled

R32 (20h)

6:0

LOPGAVOL

[6:0]

79h

(0dB)

LOPGA Volume

(See Table 28 for output PGA volume

control range)

OPVU[3]

N/A

Output PGA Volume Update

Writing a 1 to this bit will update

LOPGA, ROPGA, LOUTVOL and

ROUTVOL volumes simultaneously.

ROPGAZC

ROPGA Zero Cross Enable

0 = Zero cross disabled

1 = Zero cross enabled

R33 (21h)

6:0

ROPGAVOL

[6:0]

79h

(0dB)

ROPGA Volume

(See Table 28 for output PGA volume

control range)

OPVU[0]

N/A

Output PGA Volume Update

Writing a 1 to this bit will update

LOPGA, ROPGA, LOUTVOL and

ROUTVOL volumes simultaneously.

LOZC

LOUT (Left Headphone Output) Zero

Cross Enable

0 = Zero cross disabled

1 = Zero cross enabled

R28 (1Ch)

6:0

LOUTVOL

[6:0]

00h

(mute)

LOUT (Left Headphone Output)

Volume

(See Table 28 for output PGA volume

control range)

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