CS42L51(2005) View Datasheet(PDF) - Cirrus Logic

Part Name

Description

MFG CO.

CS42L51
(Rev.:2005)

Low Power, Stereo CODEC with Headphone Amp

Cirrus Logic 

4.3.8

CS42L51

Noise Gate

The noise gate may be used to mute signal levels that fall below a programmable threshold. This prevents

the ALC from applying gain to noise. A programmable delay may be used to set the minimum time before

the noise gate attacks the signal.

*Maximum noise gate attenuation levels will depend on the gain applied in either the PGA or MIC pre-

amplifier. For example: If both +32 dB pre-amplification and +12 dB programmable gain is applied, the

maximum attenuation that the noise gate achieves will be 52 dB (-96 + 32 + 12) below full-scale.

Ramp down time to the maximum setting is affected by the SOFTx bit.

Recommended settings: For best results, enable soft ramp for the digital attenuator. When the analog in-

puts are configured for differential signals (see “Differential Inputs” on page 29), enable the NG_ALL bit

to trigger the noise gate only when both inputs fall below the threshold.

Software

Controls:

“Noise Gate Configuration & Misc. (Address 1Fh)” on page 70, “ADC Control (Address 06h)” on

page 52.

Output

(dB)

NGEN=1

-52 dB

NGEN=0

-64 dB

-80 dB

-96

-40

THRESH[2:0]

Input (dB)

Figure 13. Noise Gate Attenuation

32

DS679A2

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