Datasheet

EFFICIENCY AND THERMAL INFORMATION
100°C/W
(7)
JA DMAX
T T P C
A J
Max = Max - = 150 - 100 (0.4) = 110q °
(8)
OPERATION WITH DACS AND CODECS
FILTER FREE OPERATION AND FERRITE BEAD FILTERS
Ferrite
ChipBead
Ferrite
ChipBead
1nF
1nF
OUTP
OUTN
TPA2016D2
www.ti.com ........................................................................................................................................................ SLOS524D – JUNE 2008 – REVISED AUGUST 2009
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
JA
for the WCSP package:
Given θ
JA
of 100 ° C/W, the maximum allowable junction temperature of 150 ° C, and the maximum internal
dissipation of 0.4 W (0.2 W per channel) for 1.5 W per channel, 8- Ω load, 5-V supply, from Figure 15 , 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 42 shows typical ferrite bead and LC output filters.
Figure 42. Typical Ferrite Bead Filter (Chip bead example: TDK: MPZ1608S221A)
Copyright © 2008 – 2009, Texas Instruments Incorporated 29
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