WM8955LEFL datasheet(17/43 Pages) WOLFSON

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WM8955L

Product Preview Rev 0.4 May2003

TONE CONTROL

The WM8955L provides separate controls for bass and treble with programmable gains and filter

characteristics. This function operates on digital audio data before it is passed to the audio DACs.

Bass control can take two different forms:

•

Linear bass control: bass signals are amplified or attenuated bya user programmable

gain. This is independent of signal volume, and veryhigh bass gains on loud signals

maylead to signal clipping.

•

Adaptive bass boost: The bass volume is amplified bya variable gain. When the bass

volume is low, it is boosted more than when the bass volume is high. This method is

recommended because it prevents clipping, and usuallysounds more pleasant to the

human ear.

Treble control applies a user programmable gain, without anyadaptive boost function.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

7BB

Bass Mode

0 = Linear bass control

1 = Adaptive bass boost

Bass Filter Characteristic

0 = Low Cutoff (130 Hz at 48kHz sampling)

1 = High Cutoff (200 Hz at 48kHz sampling)

Bass Intensity

Code

BB=0

BB=1

0000

+9dB

15 (max)

0001

+9dB

0010

+7.5dB

…

(1.5dB steps)

…

0111

0dB

…

(1.5dB steps)

…

1011-1101

-6dB

4-2

1110

-6dB

1 (min)

R12 (0Ch)

Bass Control

3:0

BASS

1111 (OFF)

1111

Bypass (OFF)

Treble Filter Characteristic

0 = High Cutoff (8kHz at 48kHz sampling)

1 = Low Cutoff (4kHz at 48kHz sampling)

R13 (0Dh)

Treble Control

3:0

TRBL

1111

(Disabled)

Treble Intensity

0000 or 0001 = +9dB

0010 = +7.5dB

… (1.5dB steps)

1011 to 1110 = -6dB

1111 = Disable

Table 3 Tone Control

Note:

All cut-off frequencies change proportionallywith the DAC sample rate.

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