MAX9751 Maxim Integrated Products, Inc., MAX9751 Datasheet - Page 22

• Manufacturer Part Number: MAX9751
• Description: 2.6w Stereo Audio Power Amplifiers And Directdrive Headphone Amplifiers
• Manufacturer: Maxim Integrated Products, Inc.

resistance to an extent. See the Output Power vs.
Charge-Pump Capacitance and Load Resistance
graph in the Typical Operating Characteristics. Above
2.2µF, the on-resistance of the switches and the ESR of
C1 and C2 dominate.
The output capacitor value and ESR directly affect the
ripple at CPV
output ripple. Likewise, decreasing the ESR of C2
reduces both ripple and output resistance. Lower
capacitance values can be used in systems with low
maximum output power levels. See the Output Power
vs. Charge-Pump Capacitance and Load Resistance
graph in the Typical Operating Characteristics.
The CPV
impedance of the power supply and reduces the
impact of the MAX9750/MAX9751/MAX9755’s charge-
pump switching transients. Bypass CPV
same value as C1, and place it physically close to
CPV
for a suggested layout).
An additional benefit of the MAX9750/MAX9751/
MAX9755 is the internally generated negative supply volt-
age (CPV
MAX9751/MAX9755 to provide the negative supply for
the headphone amplifiers. It can also be used to power
other devices within a design. Current draw from CPV
should be limited to 5mA, exceeding this affects the oper-
ation of the headphone amplifier. A typical application is
a negative supply to adjust the contrast of LCD modules.
When considering the use of CPV
note that the charge-pump voltage of CPV
proportional to CPV
The charge-pump output impedance plot appears in
the Typical Operating Characteristics.
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
22
DD
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and PGND (refer to the MAX9750 Evaluation Kit
DD
SS
bypass capacitor (C3) lowers the output
). CPV
SS
Powering Other Circuits from a
. Increasing the value of C2 reduces
DD
SS
CPV
and is not a regulated voltage.
is used by the MAX9750/
DD
Bypass Capacitor (C3)
Output Capacitor (C2)
Negative Supply
SS
in this manner,
DD
SS
with C3, the
is roughly
SS
Proper layout and grounding are essential for optimum
performance. Use large traces for the power-supply
inputs and amplifier outputs to minimize losses due to
parasitic trace resistance, as well as route head away
from the device. Good grounding improves audio per-
formance, minimizes crosstalk between channels, and
prevents any switching noise from coupling into the
audio signal. Connect CPGND, PGND and GND
together at a single point on the PC board. Route
CPGND and all traces that carry switching transients
away from GND, PGND, and the traces and compo-
nents in the audio signal path.
Connect all components associated with the charge
pump (C2 and C3) to the CPGND plane. Connect V
and CPV
pump capacitors (C1, C2, and C3) as close to the
device as possible. Bypass HPV
0.1µF capacitor to GND. Place the bypass capacitors
as close to the device as possible.
Use large, low-resistance output traces. As load imped-
ance decreases, the current drawn from the device out-
puts increase. At higher current, the resistance of the
output traces decrease the power delivered to the load.
For example, when compared to a 0Ω trace, a 100mΩ
trace reduces the power delivered to a 4Ω load from
2.1W to 2W. Large output, supply, and GND traces also
improve the power dissipation of the device.
The MAX9750/MAX9751/MAX9755 thin QFN package
features an exposed thermal pad on its underside. This
pad lowers the package’s thermal resistance by provid-
ing a direct heat conduction path from the die to the
printed circuit board. Connect the exposed thermal
pad to GND by using a large pad and multiple vias to a
GND plane on the bottom of the PCB.
SS
together at the device. Place the charge-
Layout and Grounding
DD
and PV
DD
with a
SS