EFFICIENCY AND THERMAL INFORMATION

100°C/W

(7)

JA

DMAX

T

T

P

C

A

J

Max =

Max -

= 150 - 100 (0.4) = 110

q

°

(8)

OPERATION WITH DACS AND CODECS

FILTER FREE OPERATION AND FERRITE BEAD FILTERS

Ferrite

ChipBead

Ferrite

ChipBead

1nF

1nF

OUTP

OUTN

TPA2016D2

The maximum ambient temperature depends on the heat-sinking ability of the PCB system. The derating factor

for the packages are shown in the dissipation rating table. Converting this to

θ

Given

θ

dissipation of 0.4 W (0.2 W per channel) for 1.5 W per channel, 8-

Ω load, 5-V supply, from Figure 14, the

maximum ambient temperature can be calculated with the following equation.

Equation 8 shows that the calculated maximum ambient temperature is 110°C at maximum power dissipation

with a 5-V supply and 8-

Ω a load. The TPA2016D2 is designed with thermal protection that turns the device off

when the junction temperature surpasses 150°C to prevent damage to the IC. Also, using speakers more

resistive than 8-

Ω dramatically increases the thermal performance by reducing the output current and increasing

the efficiency of the amplifier.

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/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. See the functional block diagram.

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 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 37 shows typical ferrite bead and LC output filters.

Figure 37. Typical Ferrite Bead Filter (Chip bead example: TDK: MPZ1608S221A)

Copyright © 2008, Texas Instruments Incorporated

29

Product Folder Link(s): TPA2016D2