WM8737L

Preliminary Technical Data

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AI Rev 3.0 May 2004

20

Figure 7 ADC Digital Filter

The ADC digital filters contain a digital high pass filter, selectable via software control. The high-pass

filter response is detailed in the “Digital Filter Characteristics” section. When the high-pass filter is

enabled the dc offset is continuously calculated and subtracted from the input signal. By setting

HPOR, the last calculated d.c. offset value is maintained but still subtracted from the input.

The output data format can be programmed by the user to accommodate stereo or monophonic

recording on both inputs. The polarity of the output signal can also be changed under software

control. The software control is shown below.

REGISTER

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

0

ADCHPD

0

ADC High Pass Filter Enable (Digital)

1: Disable High Pass Filter

0: Enable High Pass Filter

4

HPOR

0

Store dc offset

0: Present offset maintained

1: Continuously update offset

R5 (05h)

ADC Control

6:5

POLARITY

00

00: Polarity not inverted

01: L polarity invert

10: R polarity invert

11: L and R polarity invert

Table 10 ADC Control

3D STEREO ENHANCEMENT

The WM8737L has a 3D stereo enhancement function for use in applications where the natural

separation between stereo channels is low. The function is activated by the 3DEN bit, and artificially

increases the separation between the left and right channels. The 3DDEPTH setting controls the

degree of stereo expansion. Additionally, one of four filter characteristics can be selected for the 3D

processing, using the 3DFILT control bits.

When 3D enhancement is enabled (and/or the tone control for playback) it may be necessary to

attenuate the signal by 6dB to avoid limiting. This is a user selectable function, enabled by setting

DIV2.