The MAX9716/MAX9717 audio power amplifiers are ideal
for portable audio devices with internal speakers. A
bridge-tied load (BTL) architecture minimizes external
component count, while providing high-quality audio
reproduction. Both devices deliver 1.4W continuous
power into a 4Ω load with less than 1% Total Harmonic
Distortion (THD) while operating from a single +5V supply. With an 8Ω load, both devices deliver 1W continuous
power. These devices also deliver 350mW continuous
power into an 8Ω load while operating from a single
+3.0V supply. The devices are available as adjustable
gain amplifiers (MAX9716/MAX9717A) or with internally
fixed gains of 6dB, 9dB, and 12dB (MAX9717B/
MAX9717C/MAX9717D), reducing component count.
A low-power shutdown mode disables the bias generator
and amplifiers, reducing quiescent current consumption
to less than 10nA. These devices feature Maxim’s
industry-leading, comprehensive click-and-pop suppression that reduces audible clicks and pops during
startup and shutdown.
The MAX9717 features a headphone sense input (BTL/SE)
that senses when a headphone is connected to the
device, disables the BTL slave driver, muting the speaker
while driving the headphone as a single-ended load.
The MAX9716 is pin compatible with the LM4890 and is
available in 9-bump UCSP™, 8-pin TDFN (3mm x
3mm), and 8-pin µMAX®packages. The MAX9717 is
available in 9-bump UCSP, 8-pin TDFN, and 8-pin
µMAX packages. Both devices operate over the -40°C
to +85°C extended temperature range.
Applications
Features
o 2.7V to 5.5V Single-Supply Operation
o 1.4W into 4Ω at 1% THD+N
o 10nA Low-Power Shutdown Mode
o 73dB PSRR at 1kHz
o No Audible Clicks or Pops at Power-Up/Down
o Internal Fixed Gain to Reduce Component Count
(MAX9717B/C/D)
o Adjustable Gain Option (MAX9716/MAX9717A)
o BTL /SE Input Senses when Headphones are
= ∞ connected between OUT+ and OUT-. Typical values are at TA= +25°C.) (Note 2)
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
Supply Voltage (VCCto GND) ..................................-0.3V to +6V
Any Other Pin to GND ...............................-0.3V to (V
= ∞ connected between OUT+ and OUT-. Typical values are at TA= +25°C.) (Note 2)
Note 1: Continuous power dissipation must also be observed.
Note 2: All specifications are tested at T
A
= +25°C. Specifications over temperature (TA = T
MIN
to T
MAX
) are not production tested,
and guaranteed by design.
Note 3: Quiescent power-supply current is specified and tested with no load. Quiescent power-supply current depends on the off-
set voltage when a practical load is connected to the amplifier.
Note 4: Common-mode bias voltage is the voltage on BIAS and is nominally V
CC
/2.
Note 5: V
OS
= V
OUT+
- V
OUT-.
Note 6: The amplifier input IN- is AC-coupled to GND through CIN.
Note 7: Output power is specified by a combination of a functional output current test and characterization analysis.
Note 8: Measurement bandwidth for THD+N is 22Hz to 22kHz.
Note 9: Extended short-circuit conditions result in a pulsed output.
Note 10: Time for V
The MAX9716/MAX9717 are 1.3W BTL speaker amplifiers. Both devices feature a low-power shutdown
mode, and industry-leading click-and-pop suppression.
The MAX9717 features a headphone sense input that
disables the slave BTL amplifier to drive the headphone
as a single-ended load. These devices consist of high
output-current audio amps configured as BTL amplifiers (see
Functional Diagrams
). The closed-loop gain
of the input op amp sets the single-ended gain of the
device. Two external gain resistors set the gain of the
MAX9716 and MAX9717A (see the
Gain-Setting
Resistor
section). The MAX9717B/C/D feature internally
set gains of 6dB, 9dB, and 12dB, respectively.
The output of the first amplifier serves as the input of the
second amplifier, which is configured as an inverting
unity-gain follower. This results in two outputs, identical in
amplitude, but 180° out-of-phase.
BIAS
The MAX9716/MAX9717 operate from a single 2.7V to
5.5V supply and feature an internally generated, commonmode bias voltage of VCC/2 referenced to ground. BIAS
provides both click-and-pop suppression and sets the DC
bias level for the audio outputs. The MAX9716 can be
configured as a single-ended or differential input. For single-ended input, connect the noninverting input IN+ to
BIAS externally. The MAX9717 BIAS is internally connected to the amplifier noninverting input IN+.
The MAX9717 can only be used with a
single-ended input. Always bypass BIAS to ground with a
capacitor. Choose the value of the bypass capacitor as
described in the
BIAS Capacitor
section. Do not connect
external loads to BIAS. Any load lowers the BIAS voltage,
affecting the overall performance of the device.
BTL
/SE Control Input
The MAX9717 features a headphone sense input,
BTL/SE, that enables headphone jack sensing to control the power amplifier output configuration. Driving
BTL/SE low enables the slave amplifier (OUT-). Driving
BTL/SE high disables the slave amplifier.
Shutdown Mode
The MAX9716/MAX9717 feature a low-power shutdown
mode that reduces quiescent current consumption to
10nA. Entering shutdown disables the bias circuitry,
forces the amplifier outputs to GND through an internal
20kΩ resistor. Drive SHDN low to enter shutdown
mode; drive SHDN high for normal operation.
Click-and-Pop Suppression
The MAX9716/MAX9717 feature Maxim’s industry-leading
click-and-pop suppression circuitry. During startup, the
amplifier common-mode bias voltage ramps to the DC
bias. When entering shutdown, the amplifier outputs are
pulled to GND through an internal 20kΩ resistor. This
scheme minimizes the energy present in the audio band.
————EPExposed Pad (TDFN and µMAX Only). Connect EP to GND.
NAMEFUNCTION
DC Bias Bypass Capacitor Connection. Bypass BIAS to ground with a
1µF capacitor.
Power Supply. Bypass VCC with a 1µF capacitor to ground.
CC
Bridge Amplifier Negative Output. OUT- becomes high-impedance
when BTL/SE is driven high.
BTL/Single-Ended Mode Input. Logic low sets the device in BTL mode.
Logic high sets the device in single-ended mode.
MAX9716/MAX9717
Applications Information
BTL Amplifier
The MAX9716/MAX9717 are designed to drive a load
differentially, a configuration referred to as bridge-tied
load or BTL. The BTL configuration (Figure 1) offers
advantages over the single-ended configuration, where
one side of the load is connected to ground. Driving the
load differentially doubles the output voltage compared
to a single-ended amplifier under similar conditions.
Thus, the differential gain of the device is twice the
closed-loop gain of the input amplifier. The effective
gain is given by:
Substituting 2 x V
OUT(P-P)
for V
OUT(P-P)
into the following
equations yields four times the output power due to
doubling of the output voltage:
There is no net DC voltage across the load because the
differential outputs are each biased at midsupply. This
eliminates the need for DC-blocking capacitors
required for single-ended amplifiers. These capacitors
can be large and expensive, consume board space,
and degrade low-frequency performance.
Power Dissipation and Heat Sinking
Under normal operating conditions, the MAX9716/
MAX9717 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, TAis the ambient temperature,
and θJAis the reciprocal of the derating factor in °C/W as
specified in the
Absolute Maximum Ratings
section. For
example, θJAof the TDFN package is 41°C/W.
The increase in power delivered by the BTL configuration
directly results in an increase in internal power dissipation
over the single-ended configuration. The maximum power
dissipation for a given VCCand load is given by the
following equation:
If the power dissipation for a given application exceeds
the maximum allowed for a given package, reduce
power dissipation by increasing the ground plane heatsinking capability and the size of the traces to the device
(see the
Layout and Grounding
section). Other methods
for reducing power dissipation are to reduce VCC,
increase load impedance, decrease ambient temperature, reduce gain, or reduce input signal.
Thermal-overload protection limits total power dissipation
in the MAX9716/MAX9717. Thermal protection circuitry
disables the amplifier output stage when the junction
temperature exceeds +160°C. 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.
Fixed Gain
The MAX9717B, MAX9717C, and MAX9717D feature
internally fixed gains of 6dB, 9dB, and 12dB, respectively (see the
Selector Guide
). Fixed gain simplifies
designs, reduces pin count, decreases required footprint size, and eliminates external gain-setting resistors.
Resistors RINand RFshown in the MAX9717B/C/D
External feedback resistors set the gain of the
MAX9716 and MAX9717A. Resistors RFand RIN(see
Figure 2)set the gain of the amplifier as follows:
Where AVis the desired voltage gain. Hence, an RINof
20kΩ and an RFof 20kΩ yields a gain of 2V/V, or 6dB.
R
F
can be either fixed or variable, allowing the use of a
digitally controlled potentiometer to alter the gain under
software control.
The gain of the MAX9717 in a single-ended output
configuration is half the gain when configured as BTL
output. Choose R
F
between 10kΩ and 50kΩ for the
MAX9716 and MAX9717A. Gains for the MAX9717B/C/D
are set internally.
Input Filter
CINand RINform 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 optimal
DC level. Assuming zero-source impedance, the -3dB
point of the highpass filter is:
Setting f
-3dB
too high affects the low-frequency
response of the amplifier. Use capacitors with
dielectrics that have low-voltage coefficients, such as
tantalum or aluminum electrolytic. Capacitors with highvoltage coefficients, such as ceramics, can increase
distortion at low frequencies.
Output-Coupling Capacitor
The MAX9717 require output-coupling capacitors to
operate in single-ended (headphone) mode. The output-coupling capacitor blocks the DC component of the
amplifier output, preventing DC current from flowing to
the load. The output capacitor and the load impedance
form a highpass filter with a -3dB point determined by:
As with the input capacitor, choose C
OUT
such that
f
-3dB
is well below the lowest frequency of interest.
Setting f
-3dB
too high affects the amplifier’s low-frequency response. Load impedance is a concern when
choosing C
OUT
. Load impedance can vary, changing
the -3dB point of the output filter. A lower impedance
increases the corner frequency, degrading low-frequency response. Select C
OUT
such that the worst-
case load/C
OUT
combination yields an adequate
response. Select capacitors with low ESR to minimize
resistive losses and optimize power transfer to the load.
Differential Input
The MAX9716 can be configured for a differential input.
The advantage of differential inputs is that any common-mode noise is attenuated and not passed through
the amplifier. This input improves noise rejection and
provides common-mode rejection (Figure 3). External
components should be closely matched for high
CMRR. Figure 4 shows the MAX9716 configured for a
differential input.
BIAS is the output of the internally-generated VCC/2 bias
voltage. The BIAS bypass capacitor, C
BIAS
, improves the
power-supply rejection ratio by reducing power supply
and other noise sources at the common-mode bias node.
C
BIAS
also generates the clickless/popless startup DC
bias waveform for the speaker amplifiers. Bypass BIAS
with a 1µF capacitor to GND. Larger C
BIAS
values
improve PSRR but slow down tONtime. Do not connect
external loads to BIAS.
Supply Bypassing
Proper power-supply bypassing ensures low-noise,
low-distortion performance. Connect a 1µF ceramic
capacitor from VCCto GND. Add additional bulk
capacitance as required by the application. Connect
the bypass capacitor as close to the device as possible.
Layout and Grounding
Proper PC board layout and grounding is essential for
optimizing performance. Use large traces for the
power-supply inputs and amplifier outputs to minimize
losses due to parasitic trace resistance. Large traces
also aid in moving heat away from the package. Proper
grounding improves audio performance and prevents
digital switching noise from coupling into the audio signal.
The MAX9716/MAX9717 TDFN and µMAX packages
feature exposed thermal pads on their undersides. This
pad lowers the thermal resistance of the package by
providing a direct-heat conduction path from the die to
the printed circuit board. Connect the exposed pad to
the ground plane using multiple vias, if required.
For the latest application details on UCSP construction,
dimensions, tape carrier information, printed circuit board
techniques, bump-pad layout, and recommended reflow
temperature profile, as well as the latest information on
reliability testing results, refer to the application note,
“UCSP—A Wafer-Level Chip-Scale Package” available
on Maxim’s web site at http://www.maxim-ic.com/ucsp.
For the latest package outline information and land patterns (footprints), go to www.maxim-ic.com/packages. Note that a “+”, “#”, or
“-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status.
For the latest package outline information and land patterns (footprints), go to www.maxim-ic.com/packages. Note that a "+", "#", or
"-" in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status.
For the latest package outline information and land patterns (footprints), go to www.maxim-ic.com/packages. Note that a "+", "#", or
"-" in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status.
COM MO N DIMENSIONS
SYM BOL
MIN . M AX.
A0.700.80
D2.903.10
E2.903.10
A1
0.000.05
L0.200.40
0.25 MIN.k
A20.20 REF.
PACKAG E VARIATIONS
PKG. CO DE
T633-2
T833-2
T833-3
T1033-1
T1033M K -1
T1033-2
T1433-1
ND2E2e
61.50±0.10 2.30±0.10 0.95 B S CM O 229 / W EEA0.40±0.05 1.90 REF
81.50±0.10 2.30±0.10
81.50±0.10 2.30±0.10
1.50± 0.10
1.70± 0.10 2.30±0.1014
JEDEC SPEC
0.65 B S CM O 229 / W EEC
0.65 B S CM O 229 / W EEC
2.30± 0.1010
2.30± 0.101.50±0.10
2.30± 0.10M O 229 / W EED-32.00 REF0.25±0.050.50 BSC1.50± 0.1010
For the latest package outline information and land patterns (footprints), go to www.maxim-ic.com/packages. Note that a "+", "#", or
"-" in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status.
MAX9716/MAX9717
Low-Cost, Mono, 1.4W BTL Audio
Power Amplifiers
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in
the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
21
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