WM8946 datasheet(37/173 Pages) CIRRUS

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WM8946

Rev 4.5

DF1 FILTER

3D surround

5-notch filter

DF1 filter

L/HPF

Signal Enhancement Block 1 (SE1)

The DF1 filter is part of the SE1 block. This provides a direct-form 1 standard filter, as illustrated in

Figure 17. All of the filter coefficients are programmable for the left and right channels independently.

The default coefficients give a transparent filter response.

-1

Figure 17 Direct-Form 1 Standard Filter Structure

The DF1 response is defined by the following equations:

]

[

]

[

]

[

]

[

















The DF1 filters may be enabled on the left and right channels using the SE1_DF1_L_ENA and

SE1_DF1_R_ENA register bits defined in Table 13. For the derivation of the other associated

registers, refer to the configuration tools supplied with the WM8946 Evaluation Kit.

The DF1 filter can be used to implement very complex response patterns, with specific phase and

gain responses at different frequencies. Typical applications of this type of filter include the application

of refinements or compensations to the 3D enhancement or other user-selected filters.

RETUNETM FILTER

ReTune

5-band EQ

Signal Enhancement Block 2 (SE2)

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

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