WM8944BECSSLASHR datasheet(36/165 Pages) CIRRUS

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WM8944B

Rev 4.3

RETUNE FILTER

ReTuneTM

5-band EQ

Signal Enhancement Block 2 (SE2)

HPF

The ReTune

™ filter is part of the SE2 block. This is a very advanced feature that is intended to

perform frequency linearization according to the particular needs of the application microphone,

loudspeaker or housing. The ReTune algorithms can provide acoustic equalisation and selective

phase (delay) control of specific frequency bands.

The ReTune

™ filters are enabled using the SE2_RETUNE_L_ENA and SE2_RETUNE_R_ENA

The

ReTune™ filter coefficients are programmed in registers R101 to R132. For the derivation of the

other ReTune

configuration parameters, the WISCE™ software must be used to analyse the

requirements of the application. (Refer to WISCE

™ for further information.) If desired, one or more

sets of register coefficients might be derived for different operating scenarios, and these may be

recalled and written to the CODEC registers as required in the target application. The ReTune

configuration procedure involves the generation and analysis of test signals as outlined below.

To determine the characteristics of the microphone in an application, a test signal is applied to a

loudspeaker that is in the acoustic path to the microphone. The received signal through the application

microphone is analysed and compared with the received signal from a reference microphone in order

to determine the characteristics of the application microphone.

To determine the characteristics of the loudspeaker in an application, a test signal is applied to the

target application. A reference microphone is positioned in the normal acoustic path of the

loudspeaker, and the received signal is analysed to determine how accurately the loudspeaker has

reproduced the test signal.

5-BAND EQ

ReTuneTM

5-band EQ

Signal Enhancement Block 2 (SE2)

HPF

The 5-band EQ is part of the SE2 block. This function allows 5 frequency bands to be controlled. The

upper and lower frequency bands are controlled by low-pass and high-pass filters respectively. The

middle three frequency bands are notch filters. The cut-off / centre frequency of each filter is

programmable, and up to 12dB gain or attenuation can be selected in each case.

The 5-band EQ is enabled using the SE2_5BEQ_L_ENA register bit defined in Table 14.

The 5-band EQ coefficients are programmed in registers R132 to R175. For the derivation of these

registers, refer to the WISCETM software.

Typical applications of the 5-band EQ include the selection of user-preferences for different music

types, such as ‘rock’, ‘dance’ or ‘classical’ EQ profiles.

Note that when the right channel 5BEQ filter is disabled the gains for each of the frequency

bands must be set to 0dB.

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