19-4327; Rev 0; 10/08
KIT
ATION
EVALU
E
L
B
AVAILA
Mono 7W Class D Amplifier
The MAX9737 mono 7W Class D amplifier provides a
high-performance, thermally efficient amplifier solution
that offers up to 88% efficiency at a 12V supply. The
device operates from 8V to 28V and provides a high 80dB
PSRR, eliminating the need for a regulated power supply.
Filterless modulation allows the MAX9737 to pass CE
EMI limits with 1m cables using only a low-cost ferrite
bead and small-value capacitor on each output.
Comprehensive click-and-pop suppression circuitry
reduces noise on power-up/down or into and out of
shutdown or mute.
An input op amp allows the user to create a lowpass or
highpass filter, and select an optimal gain. The internal
precharge circuit ensures clickless/popless turn-on
within 10ms.
The MAX9737 is available in the 24-pin, TQFN-EP package and is specified over the -40°C to +85°C temperature range.
Features
♦ 8V to 28V Supply Voltage Range
♦ Spread-Spectrum Modulation Enables Low-EMI
Solution
♦ Passes EMI Limit with Up to 1m of Speaker Cable
♦ High 80dB PSRR
♦ Up to 88% Efficiency Eliminates Heatsink
♦ Thermal and Output Current Protection
♦ < 1µA Shutdown Mode
♦ Click-and-Pop Suppression
♦ < 10ms Turn-On Time
♦ Space-Saving, 4mm x 4mm x 0.8mm, 24-Pin TQFN
Package
Applications
Ordering Information
2.1 Notebook PCs
PART
LCD/PDP/CRT Monitors
MAX9737ETG+
TEMP RANGE
PIN-PACKAGE
-40°C to +85°C
24 TQFN-EP*
PC Surround Speakers
+Denotes a lead-free/RoHS-compliant package.
MP3 Docking Stations
*EP = Exposed pad.
Simplified Diagram
8V TO 28V
PRECHARGE
AUDIO
INPUT
8Ω
SHDN
MAX9737
MUTE
INPUT RESISTORS AND
CAPACITORS SELECT GAIN
AND CUTOFF FREQUENCY
Pin Configuration and Typical Application Circuit appear at
end of data sheet.
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
1
MAX9737
General Description
MAX9737
Mono 7W Class D Amplifier
ABSOLUTE MAXIMUM RATINGS
PVDD to PGND.......................................................-0.3V to +30V
AGND to PGND .....................................................-0.3V to +0.3V
IN, PRE, PC, COM to AGND.....................-0.3V to (VREG + 0.3V)
MUTE, SHDN to AGND ............................................-0.3V to +6V
REG to AGND ...............................................-0.3V to (VS + 0.3V)
VS to AGND ..............................................................-0.3V to +6V
OUT+, OUT- to PGND .............................-0.3V to (PVDD + 0.3V)
C1N to PGND ..........................................-0.3V to (PVDD + 0.3V)
C1P to PGND .........................(PVDD - 0.3V) to (VCHOLD + 0.3V)
CHOLD to PGND .......................................(VC1P - 0.3V) to +36V
OUT+, OUT-, Short Circuit to PGND or PVDD ...........Continuous
Thermal Limits (Notes 1, 2)
Continuous Power Dissipation (TA = +70°C)
24-Pin TQFN Single-Layer PCB (derate 20.8mW/°C
above +70°C)........................................................1666.7mW
θJA ................................................................................48°C/W
θJC ..................................................................................3°C/W
Continuous Power Dissipation
24-Pin TQFN Multiple-Layer PCB
(derate 27.8mW/°C above +70°C) ........................2222.2mW
θJA ................................................................................36°C/W
θJC ..................................................................................3°C/W
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°C
Junction Temperature ......................................................+150°C
Lead Temperature (soldering, 10s) .................................+300°C
Note 1: Thermal performance of this device is highly dependent on PCB layout. See the Applications Information section for more detail.
Note 2: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer
board. For detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial.
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.
ELECTRICAL CHARACTERISTICS
(VPVDD = 12V, VAGND = VPGND = 0, VSHDN = VMUTE = 5V, C1 = 0.1µF, CIN = 0.47µF, C2 = CCOM = CREG = 1µF, RIN = RFB = 20kΩ,
RL = ∞, AC measurement bandwidth 22Hz to 22kHz, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.)
(Note 3)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
AMPLIFIER DC CHARACTERISTICS
Speaker-Supply Voltage Range
PVDD
Undervoltage Lockout
UVLO
Quiescent Supply Current
IPVDD
Shutdown Supply Current
ISHDN
REG Voltage
VREG
Preregulator Voltage
COM Voltage
Inferred from PSRR test
8
28
6.8
TA = +25°C
15
20
25
VSHDN = 0, TA = +25°C
4.0
VS
1.94
mA
1
10
µA
4.2
4.5
V
2.16
V
4.85
VCOM
V
V
2.06
V
INPUT AMPLIFIER CHARACTERISTICS
Capacitive Drive
CL
Output Swing
Open-Loop Gain
AVO
Input Offset Voltage
VOS
No sustained oscillation
30
pF
Sinking ±1mA (Note 4)
2.05
V
88
dB
±2
mV
Input Amplifier Slew Rate
2.5
V/µs
Input Amplifier Unity-Gain
Bandwidth
3.5
MHz
2
IN to COM
_______________________________________________________________________________________
Mono 7W Class D Amplifier
(VPVDD = 12V, VAGND = VPGND = 0, VSHDN = VMUTE = 5V, C1 = 0.1µF, CIN = 0.47µF, C2 = CCOM = CREG = 1µF, RIN = RFB = 20kΩ,
RL = ∞, AC measurement bandwidth 22Hz to 22kHz, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.)
(Note 3)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
13.1
13.6
14.1
dB
3
4.6
±10
mV
OUTPUT AMPLIFIER CHARACTERISTICS
Output Amplifier Gain
AV
Preamplifier gain = 0dB (Note 7)
Output Current Limit
Output Offset
VOS
Power-Supply Rejection Ratio
PSRR
Output Power
POUT
THD + Noise
THD+N
Signal-to-Noise Ratio
Noise
SNR
VN
η
Efficiency
Click-and-Pop Level
KCP
OUT+ to OUT-, TA = +25°C
VPVDD = 8V to 28V, TA = +25°C
±2
65
f = 1kHz, 100mVP-P ripple
THD+N = 10%, RL = 8Ω (Note 5)
80
dB
88
6
THD+N = 10%, RL = 4Ω (Note 6)
7.4
W
13
POUT = 2W, f = 1kHz, RL = 8Ω (Note 5)
0.06
%
A-weighted, POUT = THD+N at 1%,
fIN = 1kHz
97
dB
A-weighted (Note 4)
100
µVRMS
POUT = 4W
85
%
Peak voltage, 32
samples/second,
A-weighted
(Notes 4, 5, 8)
Into shutdown
38
Out of shutdown
38
Into mute
38
Out of mute
Switching Frequency
dBV
38
270
Spread-Spectrum Bandwidth
300
330
±4
Thermal-Shutdown Level
Thermal-Shutdown Hysteresis
Turn-On Time
A
tON
From shutdown to full operation
kHz
kHz
+160
°C
30
°C
9
10
ms
DIGITAL INTERFACE (SHDN, MUTE)
Input-Voltage High
VINH
Input-Voltage Low
VINL
2
Input-Voltage Hysteresis
Input Leakage Current
Note 3:
Note 4:
Note 5:
Note 6:
Note 7:
V
0.8
50
TA = +25°C
V
mV
±10
µA
All devices are 100% production tested at TA = +25°C, and all temperature limits are guaranteed by design.
Amplifier inputs AC-coupled to GND.
8Ω resistive load in series with 68mH inductive load connected across OUT+ and OUT- outputs.
4Ω resistive load in series with 33µH inductive load connected across OUT+ and OUT- outputs for VPVDD ≤ 12V.
Output amplifier gain is defined as:
⎛ | (V
) − (VOUT − ) | ⎞
20 × log⎜ OUT +
⎟
| VPRE |
⎝
⎠
Note 8: Mode transition controlled by SHDN and MUTE.
_______________________________________________________________________________________
3
MAX9737
ELECTRICAL CHARACTERISTICS (continued)
Typical Operating Characteristics
(VPVDD = 12V, VGND = VPGND = 0, V SHDN = V MUTE = 5V, RIN = RFB = 20kΩ, unless otherwise noted.)
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
PVDD = 12V,
8Ω LOAD
10
MAX9737 toc02
1
MAX9737 toc01
1
PVDD = 12V,
4Ω LOAD
MAX9737 toc03
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
PVDD = 12V,
8Ω LOAD
0.1
POUT = 4W
THD+N (%)
THD+N (%)
THD+N (%)
1
4W
0.1
6kHz
1kHz
0.1
POUT = 2W
2W
20Hz
0.01
0.01
10
100
1k
10k
100k
0.01
10
100
1k
10k
100k
2
3
4
5
6
7
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
PVDD = 24V,
8Ω LOAD
1
1kHz
0.1
THD+N (%)
1kHz
0.1
0.1
20Hz
20Hz
20Hz
0.01
0.01
0.01
1
2
3
4
5
6
7
8
1
0
2
OUTPUT POWER (W)
3
4
5
6
7
4
6
8
EFFICIENCY
vs. TOTAL OUTPUT POWER
MAX9737 toc07
PVDD = 12V,
8Ω LOAD
10
80
70
7
60
6
50
5
40
4
30
3
POWER DISSIPATION
EFFICEINCY (%)
80
8
POWER DISSIPATION (W)
90
EFFICIENCY
MAX9737 toc08
100
9
PVDD = 18V,
8Ω LOAD
10
9
8
7
70
EFFICIENCY
60
6
50
5
40
4
30
3
POWER DISSIPATION
2
20
2
10
1
10
1
0
0
0
20
0
1
2
3
4
5
6
TOTAL OUTPUT POWER (W)
10
OUTPUT POWER (W)
OUTPUT POWER (W)
100
EFFICEINCY (%)
2
0
8
EFFICIENCY
vs. TOTAL OUTPUT POWER
90
1kHz
6kHz
7
8
0
0
1
2
3
4
5
6
7
8
TOTAL OUTPUT POWER (W)
_______________________________________________________________________________________
POWER DISSIPATION (W)
6kHz
PVDD = 12V,
4Ω LOAD
1
6kHz
THD+N (%)
1
10
MAX9737 toc05
MAX9737 toc04
10
8
MAX9737 toc06
OUTPUT POWER (W)
PVDD = 18V,
8Ω LOAD
0
1
FREQUENCY (Hz)
10
4
0
FREQUENCY (Hz)
THD+N (%)
MAX9737
Mono 7W Class D Amplifier
12
14
16
Mono 7W Class D Amplifier
EFFICIENCY
vs. TOTAL OUTPUT POWER
9
90
8
80
7
60
EFFICIENCY
6
50
5
40
4
POWER DISSIPATION
30
3
8
7
70
EFFICIENCY
60
5
4
40
POWER DISSIPATION
30
20
2
10
1
10
1
0
0
0
1
2
3
4
5
6
7
8
0
0
2
4
6
1% THD+N
5
4
3
2
14
MAX9737 toc12
PVDD = 12V
12
14
16
12
10
8
10% THD+N
6
4
11
9
8
7
6
5
10% THD+N
4
3
2
2
1% THD+N
1
0
0
12 14 16 18 20 22 24 26 28
PVDD = 8V
10
1% THD+N
0
0
5
10
15
20
25
0
30
5
10
15
20
25
SUPPLY VOLTAGE (V)
LOAD RESISTANCE (Ω)
LOAD RESISTANCE (Ω)
INBAND OUTPUT SPECTRUM
WIDEBAND OUTPUT SPECTRUM
SUPPLY CURRENT
vs. PVDD SUPPLY VOLTAGE
-20
-40
-60
-80
-100
-120
-20
-30
-40
-50
-60
-70
10k
15k
FREQUENCY (Hz)
20k
18
16
14
12
10
8
6
-80
4
-90
2
-100
5k
20
30
MAX9737 toc16
8Ω LOAD
SUPPLY CURRENT (mA)
OUTPUT AMPLITUDE (dBV)
0
0
-10
MAX9737 toc15
8Ω LOAD
MAX9737 toc14
20
OUTPUT AMPLITUDE (dBV)
10
TOTAL OUTPUT POWER
vs. LOAD RESISTANCE
16
8Ω LOAD
f = 1kHz
0
8
TOTAL OUTPUT POWER (W)
18
TOTAL OUTPUT POWER (W)
TOTAL OUTPUT POWER (W)
10% THD+N
6
TOTAL OUTPUT POWER
vs. LOAD RESISTANCE
MAX9737 toc11
9
8
10
3
2
TOTAL OUTPUT POWER vs. PVDD
8
6
50
TOTAL OUTPUT POWER (W)
1
9
20
0
7
10
PVDD = 12V,
4Ω LOAD
TOTAL OUTPUT POWER (W)
EFFICEINCY (%)
70
MAX9737 toc10
100
MAX9737 toc13
80
10
POWER DISSIPATION (W)
PVDD = 24V,
8Ω LOAD
EFFICEINCY (%)
90
EFFICIENCY
vs. TOTAL OUTPUT POWER
POWER DISSIPATION (W)
MAX9737 toc09
0
100k
1M
10M
FREQUENCY (Hz)
100M
8
10 12 14 16 18 20 22 24 26 28
SUPPLY VOLTAGE (V)
_______________________________________________________________________________________
5
MAX9737
Typical Operating Characteristics (continued)
(VPVDD = 12V, VGND = VPGND = 0, V SHDN = V MUTE = 5V, RIN = RFB = 20kΩ, unless otherwise noted.)
Typical Operating Characteristics (continued)
(VPVDD = 12V, VGND = VPGND = 0, V SHDN = V MUTE = 5V, RIN = RFB = 20kΩ, unless otherwise noted.)
SHUTDOWN CURRENT
vs. PVDD SUPPLY VOLTAGE
SHDN ON/OFF RESPONSE
MAX9737 toc18
MAX9737 toc17
40
35
SHUTDOWN CURRENT (nA)
SHDN
1V/div
30
25
20
15
OUTPUT
5V/div
10
5
0
8
10 12 14 16 18 20 22 24 26 28
10ms/div
PVDD SUPPLY VOLTAGE (V)
PSRR
MUTE ON/OFF RESPONSE
MAX9737 toc19
PVDD = 12V + 100mVP-P
8Ω LOAD
-10
MUTE
1V/div
OUTPUT
5V/div
MAX9737 toc20
0
-20
-30
PSRR (dB)
MAX9737
Mono 7W Class D Amplifier
-40
-50
-60
-70
-80
-90
-100
10ms/div
10
100
1k
10k
100k
FREQUENCY (Hz)
6
_______________________________________________________________________________________
Mono 7W Class D Amplifier
PIN
NAME
FUNCTION
1, 17, 18
PVDD
2
CHOLD
Charge-Pump Output. Connect a 1µF capacitor to PVDD.
3, 10, 11
AGND
Analog Ground
Power Supply. Bypass PVDD to PGND with a 1µF capacitor connected to pin 1 and a 1µF capacitor
connected to pins 17 and 18.
4
MUTE
Mute Input. Drive MUTE low to place the device in mute mode.
5
SHDN
Shutdown Input. Drive SHDN low to place the part in shutdown mode.
6
PC
Input Capacitor Precharge Connection. Connect between input resistor, RIN, and input coupling
capacitor, CIN.
7
IN
Op Amp Inverting Input.
8
PRE
Op Amp Output. PRE is the output of the input operational amplifier.
9
COM
Internal 2.0V Bias. Bypass COM to AGND with a 1µF capacitor.
12
REG
Internal 4.2V Bias. Bypass REG to AGND with a 1µF capacitor.
13, 14
VS
15
C1N
16
C1P
Charge-Pump, Flying-Capacitor Positive Terminal. Connect C1P to C1N through a 0.1µF capacitor.
19, 20
OUT-
Negative Speaker Output
21, 22
PGND
Power Ground
23, 24
OUT+
Positive Speaker Output
—
EP
Internal 5.0V Bias. Bypass VS to AGND with a 1µF capacitor.
Charge-Pump, Flying-Capacitor Negative Terminal. Connect C1N to C1P through a 0.1µF capacitor.
Exposed Pad. Must be externally connected to PGND.
Detailed Description
The MAX9737 filterless, mono class D audio power
amplifier offers Class AB audio performance and Class
D efficiency with minimal board space. The device
operates from an 8V to 28V supply range.
The MAX9737 features filterless, spread-spectrum
modulation, externally set gain and a low-power shutdown mode that reduces supply current to less than
1µA. Comprehensive click-and-pop suppression and
precharge circuitry reduce noise into and out of shutdown or mute within 10ms.
Spread-Spectrum Modulation
The MAX9737 features a unique spread-spectrum
switching modulation that flattens EMI wideband spectral components, reducing radiated emissions from the
speaker and cables. The switching frequency of the
Class D amplifier varies randomly by ±4kHz around the
300kHz center frequency. Instead of a large amount of
spectral energy present at multiples of the switching
frequency, the energy is spread over a bandwidth that
increases with frequency. Above a few MHz, the wideband spectrum looks like white noise for EMI purposes.
A proprietary amplifier topology ensures this white
noise does not corrupt the noise floor in the audio
bandwidth.
Efficiency
The high efficiency of a Class D amplifier is due to the
output transistors acting as switches and therefore consume negligible power. Power loss associated with the
Class D output stage is due to the MOSFET I2R losses,
switching losses, and quiescent current.
Although the theoretical best efficiency of a linear
amplifier is 78% at peak output power, under typical
music reproduction levels, the efficiency falls to below
40%. The MAX9737 exhibits > 80% efficiency under the
same conditions (Figure 1).
Shutdown
The MAX9737 features a shutdown mode that reduces
power consumption to less than 1µA (typ), extending
battery life in portable applications. Drive SHDN low to
place the device in low-power shutdown mode. In shutdown mode, the outputs are high impedance and the
common-mode voltage at the output decays to zero.
_______________________________________________________________________________________
7
MAX9737
Pin Description
Mute Function
EFFICIENCY
vs. OUTPUT POWER
The MAX9737 features a mute mode where the signal is
attenuated at the speaker and the outputs stop switching. To mute the MAX9737, drive MUTE low.
100
Click-and-Pop Suppression
80
The MAX9737 features comprehensive click-and-pop
suppression and precharge circuitry that reduce audible transients on startup and shutdown. The precharge
circuit enables the amplifier within 10ms without any
clicks or pops. Connect PC between the input resistor
(RIN) and the input capacitor (CIN). For optimal clickand-pop suppression, use a 0.47µF input coupling
capacitor (CIN).
70
EFFICIENCY (%)
90
50
CLASS AB
40
20
10
0
Current Limit
When output current exceeds the current limit, 4.6A
(typ), the MAX9737 disables the outputs and initiates a
450µs startup sequence. The shutdown and startup
sequence is repeated until the output fault is removed.
Properly designed applications do not enter currentlimit mode unless the output is short circuited or connected incorrectly.
MAX9737
60
30
0
Applications Information
Filterless Class D Operation
The MAX9737 meets EN55022B EMC radiation limits
with an inexpensive ferrite bead and capacitor filter
when the speaker leads are less than or equal to 1m
(Figure 3). Select a ferrite bead with 100Ω to 600Ω
impedance, and rated for 2A. The capacitor value
varies based on the ferrite bead chosen and the speaker lead length. See Figure 2 for the correct connections
of these components.
2
3
4
5
6
7
8
Figure 1. MAX9737 Efficiency vs. Class AB Efficiency
FB1
MAX9737
Thermal Shutdown
When the die temperature exceeds the thermal-shutdown threshold, +160°C (typ), the MAX9737 outputs
are disabled. When the die temperature decreases by
30°C, normal operation resumes. Some causes of thermal shutdown are excessively low load impedance,
poor thermal contact between the MAX9737’s exposed
pad and the PCB, elevated ambient temperature, or
poor PCB layout and assembly.
1
OUTPUT POWER (W)
C1
330pF
FB2
C2
330pF
FB1 AND FB2: WURTH742792040
Figure 2. Ferrite Bead Filter Configuration
40
35
AMPLITUDE (dBμV/m)
MAX9737
Mono 7W Class D Amplifier
EN55022B LIMIT
30
25
20
15
10
5
0
30
100
1000
FREQUENCY (MHz)
Figure 3. MAX9737 EMI Performance with 1m Twisted-Pair
Speaker Cable
Table 1. Suggested Values for LC Filter
8
RL (Ω)
L1, L2 (µH)
C1 (µF)
C2, C3 (µF)
C4, C5 (µF)
R1, R2 (Ω)
4
10
0.47
0.10
0.22
10
8
15
0.15
0.15
0.15
15
_______________________________________________________________________________________
Mono 7W Class D Amplifier
C2
Component Selection
Gain-Setting Resistors
The output stage provides a fixed internal gain in addition to the externally set input stage gain. The fixed-output stage gain is set at 13.6dB (4.8V/V). Set overall gain
by using resistors RF and RIN (Figure 5) as follows:
⎛R ⎞
A V = -4.8 ⎜ F ⎟ V / V
⎝ RIN ⎠
where A V is the desired voltage gain. Choose R F
between 10kΩ and 50kΩ.
The PRE terminal is an operational amplifier output,
allowing the MAX9737 to be configured as a filter or an
equalizer.
Input Capacitor
An input capacitor, CIN, in conjunction with the input
resistor, RIN, of the MAX9737 forms 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 negligible
source impedance, the -3dB point of the highpass filter
is given by:
f -3dB =
1
2πRINCIN
R1
L1
RL
C1
MAX9737
L2
C3
Inductor-Based Output Filters
Some applications use the MAX9737 with a full inductor/capacitor-based (LC) output filter. See Figure 4 for
the correct connections of these components.
The load impedance of the speaker determines the filter component selection (see Table 1).
Inductors L1 and L2 and capacitor C1 form the primary
output filter. Capacitors C2 and C3 provide commonmode filtering to reduce radiated emissions. Capacitors
C4 and C5, plus resistors R1 and R2, form a Zobel at
the output. A Zobel corrects the output loading to compensate for the rising impedance of the loudspeaker.
Without a Zobel, the filter exhibits peaking near the cutoff frequency.
C4
MAX9737
When evaluating the MAX9737 with a ferrite bead filter
and resistive load, include a series inductor (68µH for
8Ω load and 33µH for 4Ω load) to model typical loudspeaker’s behavior. Omitting the series inductor
reduces the efficiency, the THD+N performance and
the output power of the MAX9737. When evaluating
with a loudspeaker, no series inductor is required.
C5
R2
Figure 4. LC Filter Configuration
RF
CIN
AUDIO
INPUT
RIN
PRE
IN
OUT+
COM
OUT-
CCOM
PC
MAX9737
Figure 5. Preamplifier Gain Configuration
Choose CIN such that f-3dB is well below the lowest frequency of interest. To reduce low-frequency distortion,
use capacitors whose dielectrics have low-voltage
coefficients. Capacitors with high-voltage coefficients
cause increased distortion close to f-3dB. For best clickand-pop suppression, use a 0.47µF input capacitor.
COM Capacitor
COM is the output of the internally generated DC bias
voltage. Bypass COM with a 1µF capacitor to AGND.
Regulator Capacitor
REG is the output of the internally generated DC bias
voltage. Bypass REG with a 1µF capacitor to AGND.
Power Supplies
The MAX9737 features separate supplies for signal and
power portions of the device, allowing for the optimum
combination of headroom, power dissipation and noise
immunity. The speaker amplifiers are powered from
PVDD and can range from 8V to 28V. The remainder of
the device is powered by an internal 5V regulator, VS.
Internal Regulator
The MAX9737 features an internal 5V regulator, VS,
powered from PVDD. Bypass VS with a 1µF capacitor to
AGND.
_______________________________________________________________________________________
9
Mono 7W Class D Amplifier
MAX9737
Typical Application Circuit
8V TO 28V
1μF
REG 12
1μF
RFB
20kΩ
RIN
20kΩ
CCOM
1μF
1μF
VS
PVDD
13, 14
1, 17, 18
100μF
C1
0.1μF
1μF
CHARGE
PUMP
REGULATOR
CREG
PRE
8
IN
7
23, 24 OUT+
9
19, 20 OUT-
BIAS
PC 6
PRECHARGE
AUDIO
INPUT
MAX9737
CONTROL
CIN
0.47μF
5
SHDN
LOGIC INPUT
SHDN
3, 10, 11
4
MUTE
Supply Bypassing, Layout, and Grounding
Proper layout and grounding are essential for optimum
performance. Use wide traces for the power-supply
inputs and amplifier outputs to minimize losses due to
parasitic trace resistance. Proper grounding improves
audio performance, minimizes crosstalk between channels, and prevents switching noise from coupling into
the audio signal. Connect PGND and AGND together at
a single point on the PCB. Route all traces that carry
switching transients away from AGND and the
traces/components in the audio signal path.
Bypass PVDD with two 1µF capacitors to PGND. Place
the bypass capacitors as close as possible to the
MAX9737. Place a 100µF capacitor between PVDD and
PGND. Bypass VS, VCOM, and VREG with a 1µF capacitor
to AGND.
10
2 CHOLD
POWER
STAGE
COM
C2
1μF
C1N
15
C1P
16
AGND
21, 22
PGND
VS
Use wide, low-resistance output traces. Current drawn
from the outputs increases as load impedance
decreases. High-output trace resistance decreases the
power delivered to the load. The MAX9737 TQFN package features an exposed thermal pad on its underside.
This pad lowers the package’s thermal resistance by
providing a heat conduction path from the die to the
PCB. Connect the exposed thermal pad to PGND by
using a large pad and multiple vias to the PGND plane.
______________________________________________________________________________________
Mono 7W Class D Amplifier
Chip Information
PVDD
OUT+
OUT+
PGND
PGND
OUT-
OUT-
PROCESS: BiCMOS
TOP VIEW
24
23
22
21
20
19
1
18
PVDD
+
CHOLD
2
17
PVDD
AGND
3
16
C1P
MUTE
4
15
C1N
SHDN
5
14
VS
PC
6
13
VS
MAX9737
10
11
12
AGND
REG
PRE
9
AGND
8
COM
7
IN
*EP
TQFN
4mm x 4mm
*EP = EXPOSED PAD, CONNECT TO PGND
______________________________________________________________________________________
11
MAX9737
Pin Configuration
Package Information
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.
PACKAGE TYPE
PACKAGE CODE
DOCUMENT NO.
24 TQFN-EP
T2444+4
21-0139
24L QFN THIN.EPS
MAX9737
Mono 7W Class D Amplifier
12
______________________________________________________________________________________
Mono 7W Class D Amplifier
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.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 13
© 2008 Maxim Integrated Products
is a registered trademark of Maxim Integrated Products, Inc.
MAX9737
Package Information (continued)
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.
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