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參數(shù)資料
| 型號： | MAX9720BEUE |
| 廠商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分類： | 音頻／視頻放大 |
| 英文描述： | 50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown |
| 中文描述： | 0.05 W, 2 CHANNEL, AUDIO AMPLIFIER, PDSO16 |
| 封裝： | 4.40 MM, MO-153AB, TSSOP-16 |
| 文件頁數(shù)： | 15/21頁 |
| 文件大?。?/td> | 508K |
| 代理商： | MAX9720BEUE |
Applications Information
Power Dissipation
Under normal operating conditions, linear power ampli-
fiers can dissipate a significant amount of power. The
maximum power dissipation for each package is given
in the
Absolute Maximum Ratings
section under
Continuous Power Dissipation or can be calculated by
the following equation:
where T
J(MAX)
is +150
°
C, T
A
is the ambient temperature,
and
θ
JA
is the reciprocal of the derating factor in
°
C/W as
specified in the
Absolute Maximum Ratings
section. For
example,
θ
JA
of the TSSOP package is +106.38
°
C/W.
The MAX9720 has two power dissipation sources: the
charge pump and the two amplifiers. If the power dissipa-
tion for a given application exceeds the maximum
allowed for a given package, either reduce V
DD
, increase
load impedance, decrease the ambient temperature, or
add heat sinking to the device. Large output traces
improve the maximum power dissipation in the package.
Thermal overload protection limits total power dissipa-
tion in the MAX9720. When the junction temperature
exceeds +140
°
C, the thermal protection circuitry dis-
ables the amplifier output stage. The amplifiers are
enabled once the junction temperature cools by 15
°
C,
resulting in a pulsing output under continuous thermal
overload conditions.
Output Power
The MAX9720 is specified for the worst-case condi-
tion
—
when both inputs are in phase. Under this condi-
tion, the amplifiers simultaneously draw current from
the charge pump, leading to a slight loss in headroom
of V
SS
. In typical stereo audio applications, the left and
right signals present differences in both magnitude and
phase, subsequently leading to an increase in the max-
imum attainable output power. Figure 8 shows the two
extreme cases for in- and out-of-phase. In reality, the
available power lies between these extremes.
Powering Other Circuits from
a Negative Supply
An additional benefit of the MAX9720 is the internally
generated, negative supply voltage (PV
SS
). PV
SS
is the
negative supply for the MAX9720 headphone amplifiers.
PV
SS
can power other devices within a system. Limit the
current drawn from PV
SS
to 5mA. Exceeding this affects
the operation of the headphone amplifiers. A typical
application is a negative supply to adjust the contrast of
LCD modules.
The charge-pump voltage at PV
SS
is roughly propor-
tional to V
DD
and is not a regulated voltage. Consider
the charge-pump output impedance when powering
other devices from PV
SS
. See the Charge-Pump Output
Impedance graph in the
Typical Operating
Characteristics
. Use 2.2μF charge-pump capacitors for
the highest output power; 1μF or lower capacitors can
also be used for most applications. See the Output
Power vs. Load Resistance and Charge-Pump
Capacitance graph for details of the output power vs.
capacitor size.
Component Selection
Input Filtering
The input capacitor (C
IN
), in conjunction with the
MAX9720 input impedance, forms a highpass filter that
removes the DC bias from an incoming signal (see
Typical Application Circuit
). 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
IN
is the amplifier
’
s internal input impedance value
given in the
Electrical Characteristics
. Chose C
IN
such
that f
-3dB
is well below the lowest frequency of interest.
Setting f
-3dB
too high affects the amplifier
’
s low-fre-
quency response. Use capacitors whose dielectrics
have low-voltage coefficients, such as tantalum or alu-
minum electrolytic. Capacitors with high-voltage coeffi-
cients, such as ceramics, may result in increased
distortion at low frequencies.
f
R C
π
dB
=
3
1
2
P
T
T
DISSPKG MAX
J MAX
(
A
JA
(
)
)
=
θ
M
50mW, DirectDrive, Stereo Headphone
Amplifier with SmartSense and Shutdown
______________________________________________________________________________________
15
100
0.001
0
40
20
80
120
160
140
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT POWER
0.01
0.1
1
10
OUTPUT POWER (mW)
T
60
100
V
DD
= 3V
A
= -1V/V
f = 1kHz
R
L
= 16
OUTPUTS
IN PHASE
SINGLE-
CHANNEL
OUTPUTS
OUT OF
PHASE
Figure 8. THD+N vs. Output Power with Inputs In-/Out-of-Phase
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| MAX9721AEBC | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
| MAX9721AEBC-T | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
| MAX9721AETC | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
| MAX9721AETC+ | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
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