max9710etpt Maxim Integrated Products, Inc., max9710etpt Datasheet - Page 8

• Manufacturer Part Number: max9710etpt
• Description: 3w Mono/stereo Btl Audio Power Amplifiers With Shutdown
• Manufacturer: Maxim Integrated Products, Inc.

Under normal operating conditions, the MAX9710/
MAX9711 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
and θ
specified in the Absolute Maximum Ratings section. For
example, θ
48.1°C/W.
The increase in power delivered by the BTL configura-
tion directly results in an increase in internal power dis-
sipation over the single-ended configuration. The
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 heat sinking to the device (see
Layout and Grounding section). 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 the MAX9710/MAX9711. When the junction
temperature exceeds +160°C, the thermal protection
circuitry disables the amplifier output stage. The
amplifiers are enabled once the junction temperature
cools by 15°C. A pulsing output under continuous
thermal-overload conditions results as the device heats
and cools.
External feedback components set the gain of both
devices. Resistors R
the gain of the amplifier as follows:
3W Mono/Stereo BTL Audio Power Amplifiers
with Shutdown
8
DD
_______________________________________________________________________________________
, increase load impedance, decrease the ambient
JA
J(MAX
is the reciprocal of the derating factor in °C/W as
Power Dissipation and Heat Sinking
JA
P
) is +150°C, T
DISSPKG MAX
of the 20-pin thin QFN package is
P
DISS MAX
F
A
(
and R
VD
(
= ×
A
)
)
Component Selection
2
=
IN
is the ambient temperature,
=
T
(Functional Diagram) set
2
J MAX
Gain-Setting Resistors
R
R
π
(
V
IN
2
F
DD
R
θ
JA
L
2
)
−
T
A
DD
and load is
The input capacitor (C
a highpass filter that removes the DC bias from an
incoming signal. 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:
For optimum click-and-pop suppression, choose:
where R
Setting f
response of the amplifier. Use capacitors with
dielectrics that have low-voltage coefficients, such as
tantalum or aluminum electrolytic. Capacitors with high-
voltage coefficients, such as ceramics, may result in an
increase of distortion at low frequencies.
BIAS is the output of the internally generated 2.5VDC
bias voltage. The BIAS bypass capacitor, C
improves 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
DC bias waveform for the speaker amplifiers. Bypass
BIAS with a 1µF capacitor to GND. Smaller values of
C
increased click/pop levels.
Proper power-supply bypassing ensures low-noise,
low-distortion performance. Place a 0.1µF ceramic
capacitor from V
capacitance as required by the application. Locate the
bypass capacitor as close to the device as possible.
Low-profile piezoelectric speakers can provide quality
sound for portable electronics. However, piezoelectric
speakers typically require large voltage swings
(>8V
audible sound pressure levels. The MAX9711 can be
configured to drive a piezoelectric speaker with up to
10V
Figure 2 shows the THD+N of the MAX9711 driving a
piezoelectric speaker. Note that as frequency increas-
es, the THD+N increases. This is due to the capacitive
nature of the piezoelectric speaker; as frequency
increases, the speaker impedance decreases, resulting
in a larger current draw from the amplifier.
BIAS
P-P
P-P
produce faster t
while operating from a single 5V supply.
BIAS
) across the speaker element to produce
-3dB
= 50kΩ.
R
too high affects the low-frequency
IN
DD
Piezoelectric Speaker Driver
f
x C
−
3
dB
IN
IN
to PGND. Add additional bulk
ON
), in conjunction with R
< R
=
/t
2π
OFF
BIAS
R C
IN IN
1
times but may result in
x C
Supply Bypassing
BIAS
BIAS Capacitor
Input Filter
IN
, forms
BIAS
,