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SLOS417B – OCTOBER 2003 – REVISED JULY 2006
Decoupling Capacitor (C
S
)
The TPA2010D1 is a high-performance class-D audio amplifier that requires adequate power supply decoupling
to ensure the efficiency is high and total harmonic distortion (THD) is low. For higher frequency transients,
spikes, or digital hash on the line, a good low equivalent-series-resistance (ESR) ceramic capacitor, typically 1
µF, placed as close as possible to the device V
DD
lead works best. Placing this decoupling capacitor close to the
TPA2010D1 is very important for the efficiency of the class-D amplifier, because any resistance or inductance in
the trace between the device and the capacitor can cause a loss in efficiency. For filtering lower-frequency noise
signals, a 10 µF or greater capacitor placed near the audio power amplifier would also help, but it is not required
in most applications because of the high PSRR of this device.
Input Capacitors (C
I
)
The TPA2010D1 does not require input coupling capacitors if the design uses a differential source that is biased
from 0.5 V to V
DD
– 0.8 V (shown in
If the input signal is not biased within the recommended
common-mode input range, if needing to use the input as a high pass filter (shown in
or if using a
single-ended source (shown in
input coupling capacitors are required.
The input capacitors and input resistors form a high-pass filter with the corner frequency, f
c
, determined in
1
fc
+
2p R C
I I
(2)
The value of the input capacitor is important to consider as it directly affects the bass (low frequency)
performance of the circuit. Speakers in wireless phones cannot usually respond well to low frequencies, so the
corner frequency can be set to block low frequencies in this application.
is reconfigured to solve for the input coupling capacitance.
1
C
+
I
2p R f c
I
(3)
If the corner frequency is within the audio band, the capacitors should have a tolerance of ±10% or better,
because any mismatch in capacitance causes an impedance mismatch at the corner frequency and below.
For a flat low-frequency response, use large input coupling capacitors (1 µF). However, in a GSM phone the
ground signal is fluctuating at 217 Hz, but the signal from the codec does not have the same 217 Hz fluctuation.
The difference between the two signals is amplified, sent to the speaker, and heard as a 217 Hz hum.
To Battery
Internal
Oscillator
+
Differential
Input
-
R
I
IN-
_
R
I
+
IN+
Bias
Circuitry
GND
TPA2010D1
Filter-Free Class D
PWM
H-
Bridge
V
DD
C
S
V
O+
V
O-
SHUTDOWN
Figure 27. Typical TPA2010D1 Application Schematic With Differential Input for a Wireless Phone
10
TI [ TEXAS INSTRUMENTS ]
