CS47L24 datasheet(52/256 Pages) CIRRUS

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CS47L24

Rev 4.1

5-BAND PARAMETRIC EQUALISER (EQ)

The digital core provides two EQ processing blocks as illustrated in Figure 17. A 4-input mixer is associated with each

EQ. The 4 input sources are selectable in each case, and independent volume control is provided for each path. Each

EQ block supports 1 output.

The EQ provides selective control of 5 frequency bands as described below.

The low frequency band (Band 1) filter can be configured either as a peak filter or a shelving filter. When configured as a

shelving filter, it provides adjustable gain below the Band 1 cut-off frequency. As a peak filter, it provides adjustable gain

within a defined frequency band that is centred on the Band 1 frequency.

The mid frequency bands (Band 2, Band 3, Band 4) filters are peak filters, which provide adjustable gain around the

respective centre frequency.

The high frequency band (Band 5) filter is a shelving filter, which provides adjustable gain above the Band 5 cut-off

frequency.

EQnMIX_VOL2

EQnMIX_VOL3

EQnMIX_VOL4

EQnMIX_VOL1

EQnMIX_SRC1

EQnMIX_SRC3

EQnMIX_SRC4

EQnMIX_SRC2

EQ1 (50h)

EQ2 (51h)

5-band Equaliser

CS47L24 supports 2 EQ blocks, ie. n = 1 or 2

Figure 17 Digital Core EQ Blocks

The EQ1 and EQ2 mixer control registers (see Figure 17) are located at register addresses R2176 (880h) through to

R2191 (88Eh).

The full list of digital mixer control registers is provided in the “Register Map” section (Register R1600 through to R3000).

Generic register definitions are provided in Table 7.

The *_SRCn registers select the input source(s) for the respective EQ processing blocks. Note that the selected input

source(s) must be configured for the same sample rate as the EQ to which they are connected. Sample rate conversion

functions are available to support flexible interconnectivity -

see “Asynchronous Sample Rate Converter (ASRC)” and

“Isochronous Sample Rate Converter (ISRC)”.

The bracketed numbers in Figure 17,

e.g.,”(50h)” indicate the corresponding *_SRCn register setting for selection of that

signal as an input to another digital core function.

The sample rate for the EQ function is configured using the FX_RATE register - see Table 21. Note that the EQ, DRC

and LHPF functions must all be configured for the same sample rate.

The EQ function supports audio sample rates in the range 8kHz to 192kHz. When the DRC is enabled, the maximum

sample rate for the EQ, DRC and LHPF functions is 96kHz.

Sample rate conversion is required when routing the EQ signal paths to any signal chain that is asynchronous and/or

configured for a different sample rate.

The control registers associated with the EQ functions are described in Table 9.

The cut-off or centre frequencies for the 5-band EQ are set using the coefficients held in the registers identified in Table 8.

These coefficients are derived using tools provided in Cirrus Logic

’s WISCE™ evaluation board control software; please

contact your local Cirrus Logic representative for more details.

EQ1

R3602 (0E10h) to R3620 (0E24h)

EQ2

R3624 (0E28h) to R3642 (0E3Ah)

Table 8 EQ Coefficient Registers

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