Datasheet
Trace Width
EFFICIENCY AND THERMAL INFORMATION
q
JA
+
1
Derating Factor
+
1
0.041
+ 24°CńW
(3)
T
A
Max + T
J
Max * q
JA
P
Dmax
+ 150 * 24 (1.5) + 114°C
(4)
OPERATION WITH DACs AND CODECs
FILTER FREE OPERATION AND FERRITE BEAD FILTERS
1 nF
Ferrite
Chip Bead
OUTP
OUTN
Ferrite
Chip Bead
1 nF
TPA2012D2
SLOS438D – DECEMBER 2004 – REVISED JUNE 2008 ..................................................................................................................................................
www.ti.com
Recommended trace width at the solder balls is 75 µ m to 100 µ m to prevent solder wicking onto wider PCB
traces.
For high current pins (PV
DD
, PGND, and audio output pins) of the TPA2012D2, use 100- µ m trace widths at the
solder balls and at least 500- µ m PCB traces to ensure proper performance and output power for the device.
For the remaining signals of the TPA2012D2, use 75- µ m to 100- µ m trace widths at the solder balls. The audio
input pins (INR+/- and INL+/-) must run side-by-side to maximize common-mode noise cancellation.
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 QFN package:
Given θ
JA
of 24 ° C/W, the maximum allowable junction temperature of 150 ° C, and the maximum internal
dissipation of 1.5W (0.75 W per channel) for 2.1 W per channel, 4- Ω load, 5-V supply, from Figure 25 , the
maximum ambient temperature can be calculated with the following equation.
Equation 4 shows that the calculated maximum ambient temperature is 114 ° C at maximum power dissipation
with a 5-V supply and 4- Ω a load. The TPA2012D2 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 4- 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 Figure 33 for the 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 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 37 shows typical ferrite bead and LC output filters.
Figure 37. Typical Ferrite Chip Bead Filter (Chip bead example: TDK: MPZ1608S221A)
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Product Folder Link(s): TPA2012D2