WM1811A datasheet(87/328 Pages) WOLFSON

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Production Data

WM1811A

PD, November 2013, Rev 4.1

AIF1 - OUTPUT PATH HIGH PASS FILTER

A digital high-pass filter can be enabled in the AIF1 output paths to remove DC offsets. This filter is

enabled independently on each output channel using the register bits described in Table 37.

The HPF cut-off frequency for the AIF1 channels is set using AIF1ADC1_HPF_CUT.

In hi-fi mode, the high pass filter is optimised for removing DC offsets without degrading the bass

response and has a cut-off frequency of 3.7Hz when the sample rate (fs) = 44.1kHz.

In voice modes, the high pass filter is optimised for voice communication; it is recommended to set the

cut-off frequency below 300Hz.

Note that the cut-off frequencies scale with the AIF1 sample rate. (The AIF1 sample rate is set using

the AIF1_SR register, as described in the “Clocking and Sample Rates” section.) See Table 38 for the

HPF cut-off frequencies at all supported sample rates.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R1040 (0410h)

AIF1 ADC1

Filters

14:13

AIF1ADC1_

HPF_CUT

[1:0]

AIF1ADC output path Digital HPF cut-off

frequency (fc)

00 = Hi-fi mode (fc = 4Hz at fs = 48kHz)

01 = Voice mode 1 (fc = 64Hz at fs = 8kHz)

10 = Voice mode 2 (fc = 130Hz at fs = 8kHz)

11 = Voice mode 3 (fc = 267Hz at fs = 8kHz)

AIF1ADC1L_

HPF

AIF1ADC (Left) output path Digital HPF

Enable

0 = Disabled

1 = Enabled

AIF1ADC1R

_HPF

AIF1ADC (Right) output path Digital HPF

Enable

0 = Disabled

1 = Enabled

Table 37 AIF1 Output Path High Pass Filter

Sample

Frequency

(kHz)

Cut-Off Frequency (Hz) for given value of

AIF1ADC1_HPF_CUT or AIF2ADC_HPF_CUT

8.000

0.7

130

267

11.025

0.9

178

367

16.000

1.3

127

258

532

22.050

1.9

175

354

733

24.000

2.0

190

386

798

32.000

2.7

253

514

1063

44.100

3.7

348

707

1464

48.000

4.0

379

770

1594

88.200

7.4

696

1414

2928

96.000

8.0

758

1540

3188

Table 38 AIF1 Output Path High Pass Filter Cut-Off Frequencies

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