tda2075a Tripath Technology Inc., tda2075a Datasheet - Page 16

• Manufacturer Part Number: tda2075a
• Description: Stereo Class-t Digital Audio Amplifier Driver Using Digital Power Processingtm
• Manufacturer: Tripath Technology Inc.

Input Capacitor Selection
C
frequency pole. Typically this pole is set below 10Hz to minimize attenuation at 20Hz. C
according to:
Modulator Feedback Design
The modulator converts the signal from the input stage to the high-voltage output signal. The optimum
gain of the modulator is determined from the maximum allowable feedback level for the modulator and
maximum supply voltages for the power stage. Depending on the maximum supply voltage, the feedback
ratio will need to be adjusted to maximize performance. The values of R
explanation below) define the gain of the modulator. Once these values are chosen, based on the
maximum supply voltage, the gain of the modulator will be fixed.
For the best signal-to-noise ratio and lowest distortion, the maximum modulator feedback voltage should
be approximately 4Vpp. The modulator feedback resistor R
feedback voltage is approximately 4Vpp. This will keep the gain of the modulator as low as possible and
still allow headroom so that the feedback signal does not clip the modulator feedback stage. Increasing
the value of R
necessary to achieve full power for the amplifier since the input stage will clip at approximately 4Vpp. This
will ensure that the input stage doesn’t clip before the output stage.
Figure 3 shows how the feedback from the output of the amplifier is returned to the input of the modulator.
The input to the modulator (FBKOUT1/FBKGND1 for channel 1) can be viewed as inputs to an inverting
differential amplifier. R
large OUT1/OUT2 signal to down to 4Vpp.
I
can be calculated once a value for R
16
C
where: R
I
= 1 / (2S x F
FBC
F
will increase the modulator gain. Sometimes increasing the value of R
P
I
= Input resistor value in ohms (typically 20k:)
= Input low frequency pole (typically 3.6Hz)
1/2 TDA2075A
FBA
P
Processing
Modulation
Figure 3: Modulator Feedback
x R
and R
I
)
&
FBB
bias the feedback signal to approximately 2.5V and R
FBKGND1
FBKOUT1
I
has been determined. C
R
FBA
R
FBB
AGND
V5
T r i p a t h T e c h n o l o g y , I n c . - T e c h n i c a l I n f o r m a t i o n
FBC
R
R
should be adjusted so that the modulator
FBA
FBB
I
and R
R
R
FBC
FBC
I
FBA
determine the input low-
OUT1
OUT1 GROUND
, R
T D A 2 0 7 5 A – R e v . 0 . 9 / K L i / 1 0 . 0 5
FBB
and R
FBC
FBC
IN
FBC
is calculated
(see
may be
scales the