ACS42200 datasheet(21/89 Pages) IDT

21 / 89 page

V1.2 1/12

ACS422X00

ACS422x00

LOW-POWER, HIGH-FIDELITY, INTEGRATED CODEC

range control processing element implements limiting, dynamic range compression, and dynamic range expansion

functions.

3.6.

Limiter

The Limiter function will limit the output of the DSP module to the Class-D and DAC modules. If the signal is greater

than 0dB it will saturate at 0dB as the final processing step within the DSP module.

There are times when the user may intentionally want the output Limiter to perform this saturation, for example +6dB of

gain applied within the DSP gain control and then limited to 0dB when output to the Class-D module would result in a

clipped signal driving the speaker output. This clipped signal would obviously contribute to increased distortion on the

speaker output which from the user listening perception it would “sound louder”.

At other times, the system implementor may wish to protect speakers from overheating or provide hearing protection by

intentionally limiting the output level before full scale is reached. A limit threshold, independent of the compressor

threshold is provided for this purpose. It is expected that the limit threshold is set to a higher level than the compressor

threshold.

3.7.

Compressor

Figure 7. Gain Compressor, Output vs Input

The traditional compressor algorithm provides two functions simultaneously (depending on signal level). For higher

Input (dBFS)

-2

-4

-6

-8

-10

-12

-14

-16

-18

-20

-22

-16

-18

-20

-22

-14

-12

-10

-8

-6

-4

-2

Limit Threshold:

Compressor Threshold:

Compressor Ratio:

3:1

-14.25 dBFS

-6 dBFS

Expander Threshold:

-18 dBFS

Expander Ratio:

1:2

Expanded

Output Range

Natural Output Range

Compressed Output Range

Compressor Threshold

Expander Threshold

Limit Threshold

ACS42200 Datasheet(PDF) 21 Page - Integrated Device Technology

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