Datasheet

V -dBV
OU
T
V -dBV
IN
Increasing
Limiter
Level
Decreasing
Limiter
Level
LimiterLevel= 500mW
LimiterLevel= 630mW
= 400LimiterLevel mW
V
-dBV
O
UT
V -dBV
IN
1
:1
LargeFixedGain
Small
Fixed
Gain
Input signal initial amplitude - |Current input signal amplitude|
Output signal amplitude =
Compression ratio
(1)
0dBV | 32 dBV|
8dBV =
4
- -
-
(2)
TPA2016D2
SLOS524D – JUNE 2008 – REVISED AUGUST 2009 ........................................................................................................................................................ www.ti.com
Figure 28. Output Signal vs Input Signal State Diagram Showing Different Limiter Level Configurations
The limiter level and the fixed gain influence each other. If the fixed gain is set high, the AGC has a large limiter
range. The fixed gain is set low, the AGC has a short limiter range. Figure 29 illustrates the two examples:
Figure 29. Output Signal vs. Input Signal State Diagram Showing Same Limiter Level Configurations with
Different Fixed Gain Configurations
Compression Ratio: The compression ratio sets the relation between input and output signal outside the limiter
level region. The compression ratio compresses the dynamic range of the audio. For example if the audio source
has a dynamic range of 60dB and compression ratio of 2:1 is selected, then the output has a dynamic range of
30dB. Most small form factor speakers have small dynamic range. Compression ratio allows audio with large
dynamic range to fit into a speaker with small dynamic range.
The compression ratio also increases the loudness of the audio without increasing the peak voltage. The higher
the compression ratio, the louder the perceived audio.
For example:
• A compression ratio of 4:1 is selected (meaning that a 4dB change in the input signal results in a 1dB signal
change at the output)
• A fixed gain of 0dB is selected and the maximum audio level is at 0dBV.
When the input signal decreases to – 32dBV, the amplifier increases the gain to 24dB in order to achieve an
output of – 8dBV. The output signal amplitude equation is:
In this example:
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