TPA2028D1_17 Datasheet, PDF (19/43 Pages) Texas Instruments – 3-W Mono Class-D Audio Amplifier With Fast Gain Ramp SmartGain AGC/DRC

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Max Gain Max Gain
= 30dB = 22dB
TPA2028D1
SLOS660C – JANUARY 2010 – REVISED OCTOBER 2015
1:1
V_IN - dBV
Figure 38. Output Signal Versus Input Signal State Diagram Showing Different Maximum Gains
A particular application requiring maximum gain of 22dB, for example. Thus, set the maximum gain at 22dB. The
amplifier gain will never have a gain higher than 22dB; however, this will reduce the limiter range.
Attack, Release, and Hold time:
• The attack time is the minimum time between gain decreases.
• The release time is the minimum time between gain increases.
• The hold time is the minimum time between a gain decrease (attack) and a gain increase (release). The hold
time can be deactivated. Hold time is only valid if greater than release time.
Successive gain decreases are never faster than the attack time. Successive gain increases are never faster
than the release time.
All time variables (attack, release and hold) start counting after each gain change performed by the AGC. The
AGC is allowed to decrease the gain (attack) only after the attack time finishes. The AGC is allowed to increase
the gain (release) only after the release time finishes counting. However, if the preceding gain change was an
attack (gain increase) and the hold time is enabled and longer than the release time, then the gain is only
increased after the hold time.
The hold time is only enabled after a gain decrease (attack). The hold time replaces the release time after a gain
decrease (attack). If the gain needs to be increased further, then the release time is used. The release time is
used instead of the hold time if the hold time is disabled.
The attack time should be at least 100 times shorter than the release and hold time. The hold time should be the
same or greater than the release time. It is important to select reasonable values for those variables in order to
prevent the gain from changing too often or too slow.
Figure 39 illustrates the relationship between the three time variables.
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