CS42L56 datasheet(35/92 Pages) CIRRUS

35 / 92 page

DS851F2

CS42L56

whenever a threshold violation occurs. It then modifies the signal level by adjusting the gain settings in

the PGA and ADC digital volume control accordingly.

As shown in Figure 18, if the input signal level rises above the maximum threshold, the ALC first lowers

the PGA gain settings. It then decreases the ADC digital volume at a programmable “attack” rate and

maintains the resulting level below the maximum threshold. In contrast, if the input signal level falls below

the minimum threshold, the ALC first increases the ADC digital volume settings and then increases the

PGA gain settings at a programmable “release” rate. However, once an attack or release operation has

been performed on an input signal, the ALC does not change the PGA or the digital volume control set-

tings until the next threshold violation occurs.

Output

(after ALC)

Input (before ALC)

Total ALC

Response

ALCMAX[2:0]

ARATE[5:0]

below full scale

ALCMIN[2:0]

below full scale

ALCMIN[2:0]

below full scale

ALCMAX[2:0]

below full scale

PGA

Response

ADC Vol.

Cntrl.

Response

RRATE[5:0]

ARATE[5:0]

Figure 18. ALC Operation

CS42L56 Datasheet(PDF) 35 Page - Cirrus Logic