Datasheet

TLV320AIC3120

SLAS653A –FEBRUARY 2010–REVISED MAY 2012

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5.6.4.4 DRC Attack Rate

When the output of the DAC digital volume control exceeds the programmed DRC threshold, the gain

applied in the DAC digital volume control is progressively reduced to avoid the signal from saturating the

channel. This process of reducing the applied gain is called attack. To avoid audible artifacts, the gain is

reduced slowly with a rate equaling the attack rate, programmable via page 0 / register 70, bits D7–D4.

Attack rates can be programmed from 4-dB gain change per 1/DAC_f

to 1.2207e–5-dB gain change per

1/DAC_f

Attack rates should be programmed such that before the output of the DAC digital volume control can clip,

the input signal should be sufficiently attenuated. High attack rates can cause audible artifacts, and too-

slow attack rates may not be able to prevent the input signal from clipping.

The recommended DRC attack rate value is 1.9531e–4 dB per 1/DAC_f

5.6.4.5 DRC Decay Rate

When the DRC detects a reduction in output signal swing beyond the programmed DRC threshold, the

DRC enters a decay state, where the applied gain in the digital-volume control is gradually increased to

programmed values. To avoid audible artifacts, the gain is slowly increased with a rate equal to the decay

rate programmed through page 0 / register 70, bits D3–D0. The decay rates can be programmed from

1.5625e–3 dB per 1/DAC_f

to 4.7683e–7 dB per 1/DAC_f

. If the decay rates are programmed too high,

then sudden gain changes can cause audible artifacts. However, if it is programmed too slow, then the

output may be perceived as too low for a long time after the peak signal has passed.

The recommended Value of DRC attack rate is 2.4414e–5 dB per 1/DAC_f

5.6.4.6 Example Setup for DRC

• PGA Gain = 12 dB

• Threshold = –24 dB

• Hysteresis = 3 dB

• Hold time = 0 ms

• Attack Rate = 1.9531e–4 dB per 1/DAC_f

• Decay Rate = 2.4414e–5 dB per 1/DAC_f

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