MAX9751 Maxim Integrated Products, Inc., MAX9751 Datasheet - Page 21

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MAX9751

Manufacturer Part Number
MAX9751
Description
2.6w Stereo Audio Power Amplifiers And Directdrive Headphone Amplifiers
Manufacturer
Maxim Integrated Products, Inc.
Datasheet
Table 4. Suggested Capacitor Manufacturers
maximum power dissipation for a given V
given by the following equation:
If the power dissipation for a given application exceeds
the maximum allowed for a given package, either reduce
V
temperature, or add heatsinking to the device. Large
output, supply, and ground PC board traces improve the
maximum power dissipation in the package.
Thermal-overload protection limits total power dissipa-
tion in these devices. When the junction temperature
exceeds +160°C, the thermal-protection circuitry dis-
ables the amplifier output stage. The amplifiers are
enabled once the junction temperature cools by 15°C.
This results in a pulsing output under continuous ther-
mal-overload conditions as the device heats and cools.
The headphone amplifiers have been specified for the
worst-case scenario—when both inputs are in phase.
Under this condition, the drivers simultaneously draw
current from the charge pump, leading to a slight loss in
headroom of V
the left and right signals have differences in both magni-
tude and phase, subsequently leading to an increase in
the maximum attainable output power. Figure 10 shows
the two extreme cases for in and out of phase. In reality,
the available power lies between these extremes.
The MAX9750/MAX9751/MAX9755 have different sup-
plies for each portion of the device, allowing for the opti-
mum combination of headroom and power dissipation
and noise immunity. The speaker amplifiers are pow-
ered from PV
headphone amplifiers are powered from HPV
V
amplifiers and ranges from 3V to 5.5V. V
tive supply of the headphone amplifiers. Connect V
CPV
CPV
potential as HPV
age at CPV
CPV
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TDK
DD
SS
. HPV
, increase load impedance, decrease the ambient
DD
SS
SS
SUPPLIER
. The remainder of the device is powered by V
. The charge pump is powered by CPV
ranges from 3V to 5.5V and should be the same
Output Power (Headphone Amplifier)
DD
DD
DD
is the positive supply of the headphone
SS
, and the resulting voltage appears at
. PV
DD
P
. In typical stereo audio applications,
2.6W Stereo Audio Power Amplifiers and
______________________________________________________________________________________
DISS MAX
. The charge pump inverts the volt-
DD
(
ranges from 4.5V to 5.5V. The
)
800-348-2496
807-803-6100
=
PHONE
2
π
V
2
DD
DirectDrive Headphone Amplifiers
R
L
Power Supplies
2
SS
DD
is the nega-
and load is
DD
847-925-0899
847-390-4405
SS
and
DD
DD
to
FAX
.
.
The input capacitor (C
fier input resistance (R
removes the DC bias from an incoming signal (see the
Block Diagrams). The AC-coupling capacitor allows the
amplifier to bias the signal to an optimum DC level.
Assuming zero source impedance, the -3dB point of
the highpass filter is given by:
R
given in the Electrical Characteristics table. Choose C
such that f
interest. Setting f
low-frequency response. Use capacitors with low-volt-
age coefficient dielectrics, such as tantalum or alu-
minum electrolytic. Capacitors with high-voltage
coefficients, such as ceramics, may result in increased
distortion at low frequencies.
BIAS is the output of the internally generated DC bias
voltage. The BIAS bypass capacitor, C
PSRR and THD+N by reducing power supply and other
noise sources at the common-mode bias node, and
also generates the clickless/popless, startup/shutdown
DC bias waveforms for the speaker amplifiers. Bypass
BIAS with a 1µF capacitor to GND.
Use capacitors with an ESR less than 100mΩ for opti-
mum performance. Low-ESR ceramic capacitors mini-
mize the output resistance of the charge pump. For
best performance over the extended temperature
range, select capacitors with an X7R dielectric. Table 4
lists suggested manufacturers.
The value of the flying capacitor (C1) affects the load
regulation and output resistance of the charge pump. A
C1 value that is too small degrades the device’s ability
to provide sufficient current drive, which leads to a loss
of output voltage. Increasing the value of C1 improves
load regulation and reduces the charge-pump output
IN
is the amplifier’s internal input resistance value
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-3dB
is well below the lowest frequency of
f
-3dB
Charge-Pump Capacitor Selection
3
dB
IN
too high affects the amplifier’s
IN
=
), in conjunction with the ampli-
), forms a highpass filter that
WEBSITE
Component Selection
R C
IN IN
1
Flying Capacitor (C1)
BIAS Capacitor
Input Filtering
BIAS
, improves
21
IN

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