WM8948ECSSLASHR datasheet(60/189 Pages) WOLFSON

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WM8948

Production Data

PD, May 2011, Rev 4.1

SPEAKER PGA VOLUME CONTROL

The volume control of the left and right Speaker PGAs can be independently adjusted using the

SPKL_VOL and SPKR_VOL register fields as described in Table 34. The gain range is

-57dB to

+6dB in 1dB steps.

Note that the output from the Speaker PGA Volume control is an input to the Speaker Output control

described in the following section.

To prevent "zipper noise", a zero-cross function is provided on the Speaker PGAs. When this feature

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

period without zero-crossings, a timeout function is provided. When the zero-cross function is

enabled, the volume will update after the timeout period if no earlier zero-cross has occurred. The

timeout clock is enabled using TOCLK_ENA. See “Clocking and Sample Rates” for the definition of

this bit.

The SPK_VU bits control the loading of the Speaker PGA volume data. When SPK_VU 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 left and right Speaker PGA volume settings are both updated when a 1 is

written to either SPK_VU bit. This makes it possible to update the gain of the left and right output

paths simultaneously.

The Speaker PGA volume control register fields are described in Table 34.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R47 (2Fh)

Left SPK

volume ctrl

SPK_VU

Speaker PGA Volume Update

Writing a 1 to this bit will cause the

Left and Right Speaker PGA

volumes to be updated

simultaneously.

SPKL_ZC

Left Speaker PGA Zero Cross

Detector

0 = Change gain immediately

1 = Change gain on zero cross only

SPKL_PGA_

MUTE

Left Speaker PGA Mute

0 = Disable Mute

1 = Enable Mute

5:0

SPKL_VOL

11_1001

(0dB)

Left Speaker PGA Volume

00_0000 = -57dB gain

00_0001 = -56dB

…

11_1001 = 0dB

...

11_1111 = +6dB

(See Table 35 for volume range)

R48 (30h)

Right SPK

volume ctrl

SPK_VU

Speaker PGA Volume Update

Writing a 1 to this bit will cause the

Left and Right Speaker PGA

volumes to be updated

simultaneously.

SPKR_ZC

Right Speaker PGA Zero Cross

Detector

0 = Change gain immediately

1 = Change gain on zero cross only

SPKR_PGA_

MUTE

Right Speaker PGA Mute

0 = Disable Mute

1 = Enable Mute

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