max9752aetit Maxim Integrated Products, Inc., max9752aetit Datasheet - Page 23

• Manufacturer Part Number: max9752aetit
• Description: 2.2w, Low-emi, Stereo, Class D Power Amplifiers With Directdrive Headphone Amplifiers
• Manufacturer: Maxim Integrated Products, Inc.

Connect all components associated with the charge
pump (C2 and C3) to CPGND. Connect V
together at C2. Place the charge-pump capacitors (C1,
C2, and C3) as close to the device as possible. Bypass
HPV
capacitor and a 100µF capacitor to PGND. Place the
bypass capacitors as close to the device as possible.
Use large, low-resistance output traces. Current drawn
from the outputs increases as load impedance
decreases. High-output-trace resistance decreases the
power delivered to the load. For example, when com-
pared to a 0Ω trace, a 100mΩ trace reduces the power
delivered to a 4Ω load from 2.1W to 2.0W. Large out-
put, supply, and GND traces allow more heat to move
from the MAX9752/MAX9753/MAX9754 to the air,
reducing the thermal impedance of the system.
The MAX9752/MAX9753/MAX9754 thin QFN packages
feature exposed pads on their undersides. Connect the
exposed pad to GND with a large copper pad and mul-
tiple vias to the ground plane.
Filterless Class D amplifiers use the loudspeaker’s coil
inductance to filter out switching energy. Additionally, the
loudspeaker does not respond to the switching frequen-
cy of Class D amplifiers, nor could human ears hear
these frequencies. However, audio analyzers and oscil-
loscopes can detect these signals. On an oscilloscope,
2.2W, Low-EMI, Stereo, Class D Power Amplifiers
DD
with 1µF to GND. Bypass PV
______________________________________________________________________________________
Measuring Class D Outputs
with an Analog Analyzer
with DirectDrive Headphone Amplifiers
DD
SS
with a 0.1µF
and CPV
SS
the switching components obscure the audio signal. On
an audio analyzer they overload the input signal, degrad-
ing the measurement from the true audio performance of
the amplifier. A simple RC filter can be used (Figure 13)
to aid in evaluation of Class D amplifiers in the lab. This
circuit provides a single-pole response at 34kHz, with a
minimal insertion loss. More complex designs such as L-
C filters can provide more performance, but must be veri-
fied to ensure they do not add their own distortion
signature to the amplifier’s output.
Figure 13. Connecting a Class D Output to an Analog Analyzer
AND H-BRIDGE
MODULATOR
CLASS D
OUT_+
OUT_-
R
L
100Ω
100Ω
47nF
47nF
IN+
IN-
ANALYZER
AUDIO
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