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Decoupling Capacitor (C

Input Capacitors (C

fc +

1

2p R

(1)

C

1

2p R

c

(2)

TPA2012D2

SLOS438C – DECEMBER 2004 – REVISED MARCH 2007

The TPA2012D2 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 PV

the TPA2012D2 is 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 4.7

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.

Table 1. Gain Setting

INPUT IMPEDANCE

GAIN

GAIN

G1

G0

(V/V)

(dB)

(k

Ω)

0

0

2

6

28.1

0

1

4

12

17.3

1

0

8

18

9.8

1

1

16

24

5.2

The TPA2012D2 does not require input coupling capacitors if the design uses a differential source that is biased

high pass filtering is needed (see Figure 34), or if using a single-ended source (see Figure 35), input coupling

capacitors are required.

Equation 1.

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. Not using input capacitors can increase

output offset.

Equation 2 is used to solve for the input coupling capacitance.

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.

12

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