WM8737 datasheet(21/38 Pages) WOLFSON

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Preliminary Technical Data

WM8737L

AI Rev 3.0 May 2004

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

3DEN

3D function enable

0: disable

1: enable

4:1

3DDEPTH[3:0]

0000

Stereo depth

0000: 0% (minimum 3D effect)

0001: 6.67%

....

1110: 93.3%

1111: 100% (maximum 3D effect)

3DUC

Upper Cut-off frequency

0 = High (2.2kHz at 48kHz sampling)

1 = Low (1.5kHz at 48kHz sampling)

3DLC

Lower Cut-off frequency

0 = Low (200Hz at 48kHz sampling)

1 = High (500Hz at 48kHz sampling)

R4 (04h)

3D Control

DIV2

ADC 6dB attenuate enable

0: disabled (0dB)

1: -6dB enabled

Table 11 Stereo Enhancement Control

AUTOMATIC LEVEL CONTROL (ALC)

The WM8737L has an automatic level control that aims to keep a constant recording volume

irrespective of the input signal level. This is achieved by continuously adjusting the PGA gain so that

the signal level at the ADC input remains constant. A digital peak detector monitors the ADC output

and changes the PGA gain if necessary.

hold

time

decay

time

attack

time

input

signal

after

ALC

PGA

gain

ALC

target

level

Figure 8 ALC Operation

The ALC function is enabled using the ALCSEL[1:0] control bits in register R12. When enabled, the

recording volume can be programmed between -3dB and -18dB (relative to ADC full scale) using the

ALCL[3:0] register bits in register R12.

R13 and R14 bits HLD[3:0], DCY[3:0] and ATK[3:0] control the hold, decay and attack times,

respectively:

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