WM8948ECSSLASHR datasheet(38/189 Pages) WOLFSON

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WM8948

Production Data

PD, May 2011, Rev 4.1

The DF1 response is defined by the following equations:

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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 WM8948 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.

RETUNE

TM FILTER

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 left and right ReTune™ filters are enabled

using the SE2_RETUNE_L_ENA and SE2_RETUNE_R_ENA register bits defined in Table 14.

For the derivation of the other ReTune™ configuration parameters, the Wolfson 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

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 bandpass/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 left and right

channel parameters may be programmed individually. The 5-band EQ may be enabled on the left

channel using the SE2_5BEQ_L_ENA register bit defined in Table 14. For the derivation of the other

associated registers, refer to the WISCE software.

WM8948ECS/R Datenblatt(PDF) 38 Page - Wolfson Microelectronics plc

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