WM8994ECSSLASHR datasheet(86/363 Pages) CIRRUS

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WM8994

Rev 4.6

RETUNE MOBILE PARAMETRIC EQUALIZER (EQ)

The ReTune Mobile Parametric EQ is a circuit which can be enabled in the digital playback path of the

WM8994 audio interfaces. The function of the EQ is to adjust the frequency characteristic of the

output in order to compensate for unwanted frequency characteristics in the loudspeaker (or other

output transducer). It can also be used to tailor the response according to user preferences, for

example to accentuate or attenuate specific frequency bands to emulate different sound profiles or

environments e.g. concert hall, rock etc.

The WM8994 provides three stereo EQ circuits; these are associated with AIF1 timeslot 0, AIF1

timeslot 1 and AIF2 respectively. The EQ is enabled in these three signal paths using the register bits

described in Table 27.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R1152 (0480h)

AIF1 DAC1

EQ Gains (1)

AIF1DAC1_EQ_E

Enable EQ in AIF1DAC1 playback

path (AIF1, Timeslot 0)

0 = Disabled

1 = Enabled

R1184

(04A0h)

AIF1 DAC2

EQ Gains (1)

AIF1DAC2_EQ_E

Enable EQ in AIF1DAC2 playback

path (AIF1, Timeslot 1)

0 = Disabled

1 = Enabled

R1408 (0580h)

AIF2 EQ Gains

(1)

AIF2DAC_EQ_EN

Enable EQ in AIF2DAC playback

path

0 = Disabled

1 = Enabled

Table 27 ReTune Mobile Parametric EQ Enable

The following description of the EQ is applicable to all three EQ circuits. The associated register

control fields are described in Table 29, Table 30 and Table 31 for the respective EQs.

The EQ can be configured to operate in two modes -

“Default” mode or “ReTune Mobile” mode.

DEFAULT MODE (5-BAND PARAMETRIC EQ)

In default mode, the cut-off / centre frequencies are fixed as per Table 28. The filter bandwidths are

also fixed in default mode. The gain of the individual bands (-12dB to +12dB) can be controlled as

described in Table 29.

The cut-off / centre frequencies noted in Table 28 are applicable to a sample rate of 48kHz. When

using other sample rates, these frequencies will be scaled in proportion to the selected sample rate for

the associated Audio Interface (AIF1 or AIF2).

If AIF1 and AIF2 are operating at different sample rates, then the cut-off / centre frequencies will be

different for the two interfaces. Note that the frequencies can be set to other values by using the

features described in “ReTune Mobile Mode”.

EQ BAND

CUT-OFF/CENTRE FREQUENCY

100 Hz

300 Hz

875 Hz

2400 Hz

6900 Hz

Table 28 EQ Band Cut-off / Centre Frequencies

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