TPA3100D2_07 Datasheet, PDF (21/38 Pages) Texas Instruments – 20-W STEREO CLASS-D AUDIO POWER AMPLIFIER

TPA3100D2
www.ti.com
SLOS469D – OCTOBER 2005 – REVISED FEBRUARY 2006
APPLICATION INFORMATION (continued)
Adaptive Dynamic Range Control
TPA3100D2
TPA3100D2
Closest Competitor
Closest Competitor
t - Time = 100 ms/div
t - Time = 20 ms/div
Figure 31. 1-kHz Sine Output at 10% THD+N
Figure 32. 8-kHz Sine Output at 10% THD+N
The Texas Instruments patent-pending adaptive dynamic range control (ADRC) technology removes the notch
inherent in class-D audio power amplifiers when they come out of clipping. This effect is more severe at higher
frequencies as shown in Figure 32.
Gain setting via GAIN0 and GAIN1 inputs
The gain of the TPA3100D2 is set by two input terminals, GAIN0 and GAIN1.
The gains listed in Table 1 are realized by changing the taps on the input resistors and feedback resistors inside
the amplifier. This causes the input impedance (Z_I) to be dependent on the gain setting. The actual gain settings
are controlled by ratios of resistors, so the gain variation from part-to-part is small. However, the input impedance
from part-to-part at the same gain may shift by ±20% due to shifts in the actual resistance of the input resistors.
For design purposes, the input network (discussed in the next section) should be designed assuming an input
impedance of 12.8 kΩ, which is the absolute minimum input impedance of the TPA3100D2. At the lower gain
settings, the input impedance could increase as high as 38.4 kΩ
GAIN1
0
0
1
1
Table 1. Gain Setting
GAIN0
0
1
0
1
AMPLIFIER GAIN (dB)
TYP
20
26
32
36
INPUT IMPEDANCE
(kΩ)
TYP
32
16
16
16
INPUT RESISTANCE
Changing the gain setting can vary the input resistance of the amplifier from its smallest value, 16 kΩ± 20%, to
the largest value, 32 kΩ± 20%. As a result, if a single capacitor is used in the input high-pass filter, the -3 dB or
cutoff frequency may change when changing gain steps.
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