Datasheet

ReleaseTime
E
Limiterthreshold
GAIN
A
C
B
D
AttackTime
Limiterthreshold
Limiterthreshold
HoldTime
INPUTSIGNAL
OUTPUTSIGNAL
Limiterthreshold
TPA2016D2
SLOS524D – JUNE 2008 – REVISED AUGUST 2009 ........................................................................................................................................................ www.ti.com
The AGC works by detecting the audio input envelope. The gain changes depending on the amplitude, the limiter
level, the compression ratio, and the attack and release time. The gain changes constantly as the audio signal
increases and/or decreases to create the compression effect. The gain step size for the AGC is 0.5 dB. If the
audio signal has near-constant amplitude, the gain does not change. Figure 25 shows how the AGC works.
A. Gain decreases with no delay; attack time is reset. Release time and hold time are reset.
B. Signal amplitude above limiter level, but gain cannot change because attack time is not over.
C. Attack time ends; gain is allowed to decrease from this point forward by one step. Gain decreases because the
amplitude remains above limiter threshold. All times are reset
D. Gain increases after release time finishes and signal amplitude remains below desired level. All times are reset after
the gain increase.
E. Gain increases after release time is finished again because signal amplitude remains below desired level. All times
are reset after the gain increase.
Figure 25. Input and Output Audio Signal vs Time
Since the number of gain steps is limited the compression region is limited as well. The following figure shows
how the gain changes vs. the input signal amplitude in the compression region.
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