Heat
The addition of new features requires more and more processing
power. Higher-performing system-on-chip (SoC) processors
run a lot faster and typically consume more power and
generate more heat. Likewise, the larger LCD touchscreens in
infotainment systems can be affected by the heat generated
inside the infotainment head unit box. Therefore, Tier-1 ECU
suppliers are looking for ways to reduce the overall thermal load
inside infotainment head units.
Tier-1 ECU suppliers have been using Class-AB audio amplifiers
inside infotainment head units. However, Class-AB amplifiers are
significantly less efficient than newer Class-D amplifier designs
see Figure 2. This is important because the car's audio amplifier
is the second-largest source of heat generation inside the head
unit, just after the SoC. The more heat generated inside the
head unit's box means that designers need to include a much
larger passive radiated heat sink or a mechanical fan. Both
options exacerbate the goal to reduce overall solution size.
Figure 2: Class-AB vs. Class-D efficiency
(Courtesy of www.audioholics.com)
At the 2018 Consumer Electronics Show (CES), Texas
Instruments will be demonstrating the industry's first 2.1MHz
high switching frequency Class-D analog input automotive audio
amplifier. We designed the TPA6404-Q1 to best address the
issues related to infotainment head unit size and thermal load.
Class-D amplifiers typically switch the amplifier on and off at
~400kHz. A much higher 2.1MHz switching frequency in the
TPA6404-Q1 Class-D amplifier design enables the use of a
significantly lower inductance value for the output filter. You can
see in Figure 3 that a 2.1MHz design using a newer 3.3µH
metal alloy-type inductor (as opposed to the much larger
10µH/8.2µH needed for a 400kHz amplifier) allows all eight
inductors for a four-channel solution to fit into the same footprint
as just one 8.2µH inductor.
Figure 3: Inductor size comparison
Another key feature of the TPA6404-Q1 that helps contribute to
a small four-channel amplifier solution size is its "flow-through"
audio signal design. Figure 4 illustrates how the analog input
signals come into the amplifier device on one side of the chip;
then amplification of the audio signal takes place on the opposite
side of the device where the signals flow into the external
output filters.
Figure 4: Flow-through design of the TPA6404-Q1
17
OPA1622 SoundPlus™ Audio
Operational Amplifier
• High-Fidelity Sound Quality
• Ultra-low Noise: 2.8nV/√Hz at 1kHz
• Ultra-low Total Harmonic Distortion + Noise -119dB THD+N
(142mW/Ch into 32Ω/Ch)
Learn more
