CS47L85 datasheet(84/370 Pages) CIRRUS

84 / 370 page

CS47L85

Rev 4.3

DRCn_KNEE_IP

(Y0)

0dB

DRC

n_H

I_CO

DRCn Input Amplitude (dB)

DRCn Output Amplitude (dB)

DRCn_KNEE_OP

Knee1

Knee2

DRCn_KNEE2_IP

DRCn_KNEE2_OP

Figure 29 DRC Response Characteristic

The slope of the DRC response is determined by register fields DRCn_HI_COMP and DRCn_LO_COMP. A slope of 1

indicates constant gain in this region. A slope less than 1 represents compression (i.e. a change in input amplitude produces

only a smaller change in output amplitude). A slope of 0 indicates that the target output amplitude is the same across a

range of input amplitudes; this is infinite compression.

When the noise gate is enabled, the DRC response in this region is determined by the DRCn_NG_EXP register. A slope of

1 indicates constant gain in this region. A slope greater than 1 represents expansion (i.e., a change in input amplitude

produces a larger change in output amplitude).

When the DRCn

_KNEE2_OP knee is enabled (“Knee2” in Figure 29), this introduces the vertical line in the response pattern

illustrated, resulting in infinitely steep attenuation at this point in the response.

The DRC parameters are listed in Table 13.

REF

PARAMETER

DESCRIPTION

DRCn_KNEE_IP

Input level at Knee1 (dB)

DRCn_KNEE_OP

Output level at Knee2 (dB)

DRCn_HI_COMP

Compression ratio above Knee1

DRCn_LO_COMP

Compression ratio below Knee1

DRCn_KNEE2_IP

Input level at Knee2 (dB)

DRCn_NG_EXP

Expansion ratio below Knee2

DRCn_KNEE2_OP

Output level at Knee2 (dB)

Table 13 DRC Response Parameters

The noise gate is enabled when the DRCn_NG_ENA register is set. When the noise gate is not enabled, parameters 5, 6,

7 above are ignored, and the DRCn_LO_COMP slope applies to all input signal levels below Knee1.

The DRCn_KNEE2_OP knee is enabled when the DRCn_KNEE2_OP_ENA register is set. When this bit is not set, then

parameter 7 above is ignored, and the Knee2 position always coincides with the low end of the DRCn_LO_COMP region.

The “Knee1” point in Figure 29 is determined by register fields DRCn_KNEE_IP and DRCn_KNEE_OP.

Parameter Y0, the output level for a 0dB input, is not specified directly, but can be calculated from the other parameters,

using the equation:

Y0 = DRCn_KNEE_OP - (DRCn_KNEE_IP x DRCn_HI_COMP)

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