TPA2026D2_15 Datasheet, PDF (16/39 Pages) Texas Instruments – 3.2-W/Ch Stereo Class-D Audio Amplifier with Fast Gain Ramp SmartGain™ AGC/DRC

TPA2026D2
SLOS649A – MARCH 2010 – REVISED JANUARY 2011
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Figure 32. Input Signal Voltage vs Gain
Thus the AGC performs a mapping of the input signal vs. the output signal amplitude. This mapping can be
modified according to the variables from Table 1.
The following graphs and explanations show the effect of each variable to the AGC independently and which
considerations should be taken when choosing values.
Fixed Gain: The fixed gain determines the initial gain of the AGC. Set the gain using the following variables:
• Set the fixed gain to be equal to the gain when the AGC is disabled.
• Set the fixed gain to maximize SNR.
• Set the fixed gain such that it will not overdrive the speaker.
Figure 33 shows how the fixed gain influences the input signal amplitude vs. the output signal amplitude state
diagram. The dotted 1:1 line is displayed for reference. The 1:1 line means that for a 1dB increase in the input
signal, the output increases by 1dB.
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1:1
Increasing
Fixed Gain
Decreasing
Fixed Gain
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Figure 33. Output Signal vs Input Signal State Diagram Showing Different Fixed Gain Configurations
If the Compression function is enabled, the Fixed Gain is adjustable from –28dB to 30dB. If the Compression
function is disabled, the Fixed gain is adjustable from 0dB to 30dB.
Limiter Level: The Limiter level sets the maximum amplitude allowed at the output of the amplifier. The limiter
should be set with the following constraints in mind:
• Below or at the maximum power rating of the speaker
• Below the minimum supply voltage in order to avoid clipping
Figure 34 shows how the limiter level influences the input signal amplitude vs. the output signal amplitude state
diagram.
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