CS48L32 datasheet(53/192 Pages) CIRRUS

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DS1219F4

Cirrus Logic

CS48L32

4.3 Digital Core

The slope of the DRC response is determined by 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.

If the noise gate is enabled, the DRC response in this region is determined by DRCn_NG_EXP. 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).

If the DRCn_KNEE2_OP knee is enabled (Knee 2 in Fig. 4-20), this introduces the vertical line in the response pattern

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

The DRC parameters are listed in Table 4-14.

The noise gate is enabled by setting DRCn_NG_EN. When the noise gate is not enabled, Parameters 5–7 (see

Table 4-14) are ignored, and the DRCn_LO_COMP slope applies to all input signal levels below Knee 1.

The DRCn_KNEE2_OP knee is enabled by setting DRCn_KNEE2_OP_EN. If this bit is not set, Parameter 7 is ignored

and the Knee 2 position always coincides with the low end of the DRCn_LO_COMP region.

The Knee 1 point in Fig. 4-20 is determined by DRCn_KNEE1_IP and DRCn_KNEE1_OP.

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

using Eq. 4-2.

Equation 4-2. DRC Compression Calculation

4.3.5.2

Gain Limits

The minimum and maximum gain applied by the DRC is set by DRCn_MINGAIN, DRCn_MAXGAIN, and DRCn_NG_

MINGAIN. These limits can be used to alter the DRC response from that shown in Fig. 4-20. If the range between

maximum and minimum gain is reduced, the extent of the dynamic range control is reduced.

The minimum gain in the compression regions of the DRC response is set by DRCn_MINGAIN. The minimum gain in the

noise-gate region is set by DRCn_NG_MINGAIN. The minimum gain limit prevents excessive attenuation of the signal

path.

The maximum gain limit set by DRCn_MAXGAIN prevents quiet signals (or silence) from being excessively amplified.

4.3.5.3

Dynamic Characteristics

The dynamic behavior determines how quickly the DRC responds to changing signal levels. Note that the DRC responds

to the average (RMS) signal amplitude over a period of time.

The DRCn_ATK determines how quickly the DRC gain decreases when the signal amplitude is high. The DRCn_DCY

determines how quickly the DRC gain increases when the signal amplitude is low.

These fields are described in Table 4-15 and Table 4-16. The register defaults are suitable for general-purpose

microphone use.

Table 4-14. DRC Response Parameters

Parameters

Parameter

Description

DRCn_KNEE1_IP

Input level at Knee 1 (dB)

DRCn_KNEE1_OP

Output level at Knee 1 (dB)

DRCn_HI_COMP

Compression ratio above Knee 1

DRCn_LO_COMP

Compression ratio below Knee 1

DRCn_KNEE2_IP

Input level at Knee 2 (dB)

DRCn_NG_EXP

Expansion ratio below Knee 2

DRCn_KNEE2_OP

Output level at Knee 2 (dB)

DRCn_KNEE1_OP

DRCn_KNEE1_IP

DRCn_HI_COMP

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