TPA005D02
2-W STEREO CLASS-D AUDIO POWER AMPLIFIER
SLOS227C – AUGUST 1998 – REVISED MARCH 2000
APPLICATION INFORMATION
input capacitor, C
I
In the typical application an input capacitor, C , is required to allow the amplifier to bias the input signal to the
I
proper dc level for optimum operation. In this case, C and R , the TPA005D002’s input resistance forms a
I
IN
high-pass filter with the corner frequency determined in equation 8.
–3 dB
1
2 R
f
(8)
c(highpass)
C
IN I
R
is nominally 10 kΩ
IN
f
c
The value of C is important to consider as it directly affects the bass (low frequency) performance of the circuit.
I
Consider the example where the specification calls for a flat bass response down to 40 Hz. Equation 8 is
reconfigured as equation 9.
1
C
(9)
I
2 R
f
c
IN
In this example, C is 0.40 µF so one would likely choose a value in the range of 0.47 µF to 1 µF. A low-leakage
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tantalum or ceramic capacitor is the best choice for the input capacitors. When polarized capacitors are used,
the positive side of the capacitor should face the amplifier input as the dc level there is held at 1.5 V, which is
likely higher than the source dc level. Please note that it is important to confirm the capacitor polarity in the
application.
differential input
The TPA005D02 has differential inputs to minimize distortion at the input to the IC. Since these inputs nominally
sit at 1.5 V, dc-blocking capacitors are required on each of the four input terminals. If the signal source is
single-ended, optimal performance is achieved by treating the signal ground as a signal. In other words,
reference the signal ground at the signal source, and run a trace to the dc-blocking capacitor which should be
located physically close to the TPA005D02. If this is not feasible, it is still necessary to locally ground the unused
input terminal through a dc-blocking capacitor.
power supply decoupling, C
S
The TPA005D02 is a high-performance Class-D CMOS audio amplifier that requires adequate power supply
decoupling to ensure the output total harmonic distortion (THD) is as low as possible. Power supply decoupling
also prevents oscillations for long lead lengths between the amplifier and the speaker. The optimum decoupling
is achieved by using two capacitors of different types that target different types of noise on the power supply
leads. For higher frequency transients, spikes, or digital hash on the line, a good low equivalent-series-
resistance (ESR) ceramic capacitor, typically 0.1 µF placed as close as possible to the device’s various V
leads works best. For filtering lower-frequency noise signals, a larger aluminum electrolytic capacitor of 10 µF
DD
or greater placed near the audio power amplifier is recommended.
The TPA005D02 has several different power supply terminals. This was done to isolate the noise resulting from
high-current switching from the sensitive analog circuitry inside the IC.
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