Volume Boost - Cirrus Logic WM8940 Manual

Rev 4.4
Upper
Threshold
0.5dB
LIMLVL
0.5dB
Lower
Threshold
0dB
-0.5dB
-1dB
Figure 20 DAC Digital Limiter Operation
The limiter has a programmable upper threshold which is close to 0dB. Referring to Table 33, in
normal operation (LIMBOOST=000 => limit only) signals below this threshold are unaffected by the
limiter. Signals above the upper threshold are attenuated at a specific attack rate (set by the LIMATK
register bits) until the signal falls below the threshold. The limiter also has a lower threshold 1dB
below the upper threshold. When the signal falls below the lower threshold the signal is amplified at a
specific decay rate (controlled by LIMDCY register bits) until a gain of 0dB is reached. Both threshold
levels are controlled by the LIMLVL register bits. The upper threshold is 0.5dB above the value
programmed by LIMLVL and the lower threshold is 0.5dB below the LIMLVL value.

VOLUME BOOST

The limiter has programmable upper gain which boosts signals below the threshold to compress the
dynamic range of the signal and increase its perceived loudness. This operates as an ALC function
with limited boost capability. The volume boost is from 0dB to +12dB in 1dB steps, controlled by the
LIMBOOST register bits.
The output limiter volume boost can also be used as a stand alone digital gain boost when the limiter
is disabled.
WM8940
input
output
43