INL-

INL+

INR-

INR+

TPA2012D2

DAC or CODEC

Copyright © 2016, Texas Instruments Incorporated

14

TPA2012D2

SLOS438F – DECEMBER 2004 – REVISED MARCH 2017

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Copyright © 2004–2017, Texas Instruments Incorporated

Table 1. Gain Setting

G1

G0

GAIN

(V/V)

GAIN

(dB)

INPUT IMPEDANCE

0

0

2

6

28.1

0

1

4

12

17.3

1

0

8

18

9.8

1

1

16

24

5.2

9.3.2 Short-Circuit Protection

TPA2012D2 goes to low duty cycle mode when a short-circuit event happens. To return to normal duty cycle

mode, the device must be reset. The shutdown mode can be set through the SDL and SDR pins, or the device

can be turned off and turned on to return to normal duty cycle mode. This feature protects the device without

affecting long-term reliability.

9.3.3 Operation With DACs and CODECs

In using Class-D amplifiers with CODECs and DACs, sometimes there is an increase in the output noise floor

from the audio amplifier. This occurs when mixing of the output frequencies of the CODEC and DAC mix with the

switching frequencies of the audio amplifier input stage. The noise increase can be solved by placing a low-pass

filter between the CODEC, DAC, and audio amplifier. This filters off the high frequencies that cause the problem

and allow proper performance. The recommended resistor value is 100 Ω and the capacitor value of 47 nF.

Figure 35 shows the typical input filter.

Figure 35. Reducing Out-of-Band DAC Noise With External Input Filter

9.3.4 Filter-Free Operation and Ferrite Bead Filters

A ferrite bead filter can often be used if the design is failing radiated emissions without an LC filter and the

frequency sensitive circuit is greater than 1 MHz. This filter functions well for circuits that just have to pass FCC

and CE because FCC and CE only test radiated emissions greater than 30 MHz. When choosing a ferrite bead,

choose one with high impedance at high frequencies, and very low impedance at low frequencies. In addition,

select a ferrite bead with adequate current rating to prevent distortion of the output signal.

Use an LC output filter if there are low frequency (< 1 MHz) EMI sensitive circuits and/or there are long leads

from amplifier to speaker.

Figure 36 shows typical ferrite bead and LC output filters.