MAX9708ETN ,20W/40W, Filterless, Spread-Spectrum, Mono/Stereo, Class D AmplifierBlock Diagram22MAX9708SYNCOUT SYNCOUTFS1, FS2 MAX9708FS1, FS2SYNCSYNCRIGHTCHANNELAUDIOCLASS DCLASS ..
MAX9708ETN+ ,20W/40W, Filterless, Spread-Spectrum, Mono/Stereo, Class D AmplifierBlock DiagramMAX9708MAX97082 2SYNCOUT SYNCOUTFS1, FS2 FS1, FS2SYNCSYNCRIGHTCHANNELAUDIOCLASS DCLASS ..
MAX9709ETN , 25W/50W, Filterless, Spread-Spectrum, Stereo/Mono, Class D Amplifier
MAX9709ETN+ ,25W/50W, Filterless, Spread-Spectrum, Stereo/Mono, Class D AmplifierBlock DiagramMAX9709MAX97092 2SYNCOUTSYNCOUTFS1, FS2 FS1, FS2SYNC SYNCRIGHTCHANNELAUDIOCLASS D CLAS ..
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MAX970EEE ,Single/Dual/Quad / Micropower / Ultra-Low-Voltage / Rail-to-Rail I/O ComparatorsFeaturesThe MAX965–MAX970 single/dual/quad micropower' Ultra-Low Single-Supply Operation down to +1 ..
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MB89191PF ,8-bit Proprietary MicrocontrollerFUJITSU SEMICONDUCTORDS07-12512-7EDATA SHEET8-bit Proprietary MicrocontrollerCMOS2F MC-8L MB89190/1 ..
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MAX9708ETN
20W/40W, Filterless, Spread-Spectrum, Mono/Stereo, Class D Amplifier
General DescriptionThe MAX9708 mono/stereo, Class D audio power ampli-
fier delivers up to 2 x 21W into an 8Ωstereo mode and
1 x 42W into a 4Ωload in mono mode while offering up
to 87% efficiency. The MAX9708 provides Class AB
amplifier performance with the benefits of Class D effi-
ciency, eliminating the need for a bulky heatsink and
conserving power. The MAX9708 operates from a single
+10V to +18V supply, driving the load in a BTL configu-
ration.
The MAX9708 offers two modulation schemes: a fixed-
frequency modulation (FFM) mode, and a spread-spec-
trum modulation (SSM) mode that reduces
EMI-radiated emissions. The MAX9708 can be synchro-
nized to an external clock from 600kHz to 1.2MHz. A
synchronized output allows multiple units to be cascad-
ed in the system.
Features include fully differential inputs, comprehensive
click-and-pop suppression, and four selectable-gain set-
tings (22dB, 25dB, 29.5dB, and 36dB). A pin-program-
mable thermal flag provides seven different thermal
warning thresholds. Short-circuit and thermal-overload
protection prevent the device from being damaged
during a fault condition.
The MAX9708 is available in 56-pin TQFN (8mm x 8mm
x 0.8mm) and 64-pin TQFP (10mm x 10mm x 1.4mm)
packages, and is specified over the extended
-40°C to +85°C temperature range.
ApplicationsLCD TVsPDP TVs
AutomotivePC/HiFi Audio Solutions
Features2 x 21W Output Power in Stereo Mode
(8Ω, THD = 10%)1 x 42W Output Power in Mono Mode
(4Ω, THD = 10%)High Efficiency: Up to 87%Filterless Class D AmplifierUnique Patented Spread-Spectrum ModeProgrammable Gain (+22dB, +25dB, +29.5dB,
+36dB)High PSRR (90dB at 1kHz)Differential Inputs Suppress Common-Mode
NoiseShutdown and Mute ControlIntegrated Click-and-Pop SuppressionLow 0.1% THD+NCurrent Limit and Thermal ProtectionProgrammable Thermal FlagSYNC Input/OutputAvailable in Thermally Efficient, Space-Saving
Packages: 56-Pin TQFN and 64-Pin TQFP
MAX9708
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
Simplified Block Diagram
Ordering Information*Future product—Contact factory for availability.
**EP = Exposed paddle.
Pin Configurations appear at end of data sheet.
MAX9708
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS(PVDD= VDD= +18V, PGND = GND = 0V, CSS= 0.47µF, CREG= 0.01µF, C1 = 0.1µF, C2 = 1µF, RLOAD = ∞, MONO = low (stereo
mode), SHDN= MUTE= high, G1 = low, G2 = high (AV= 22dB), FS1 = FS2 = high (SSM), SYNCIN = low. All load resistors (RL) are
connected between OUT_+ and OUT_-, unless otherwise stated. TA= TMINto TMAX, unless otherwise noted. Typical values are at TA
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.
PVDD, VDDto PGND, GND.......................................-0.3 to +30V
PVDDto VDD..........................................................-0.3V to +0.3V
OUTR+, OUTR-, OUTL+,
OUTL- to PGND, GND...........................-0.3V to (PVDD+ 0.3V)
C1N to GND.............................................-0.3V to (PVDD+ 0.3V)
C1P to GND..............................(PVDD- 0.3V) to (CPVDD+ 0.3V)
CPVDD to GND..........................................(PVDD - 0.3V) to +40V
All Other Pins to GND.............................................-0.3V to +12V
Continuous Input Current (except PVDD, VDD, OUTR+,
OUTR-, OUTL+, and OUTL-)...........................................20mA
Continuous Power Dissipation (TA= +70°C)
56-Pin Thin QFN (derate 47.6mW/°C above +70°C)......3.81W
64-Pin TQFP (derate 43.5mW/°C above +70°C).............3.48W
Operating Temperature Range...........................-40°C to +85°C
Storage Temperature Range.............................-65°C to +150°C
Junction Temperature......................................................+150°C
Thermal Resistance (θJC)
56-Pin Thin QFN….......................................................0.6°C/W
64-Pin TQFP….................................................................2°C/W
Lead Temperature (soldering, 10s).................................+300°C
MAX9708
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
ELECTRICAL CHARACTERISTICS (continued)(PVDD= VDD= +18V, PGND = GND = 0V, CSS= 0.47µF, CREG= 0.01µF, C1 = 0.1µF, C2 = 1µF, RLOAD = ∞, MONO = low (stereo
mode), SHDN= MUTE= high, G1 = low, G2 = high (AV= 22dB), FS1 = FS2 = high (SSM), SYNCIN = low. All load resistors (RL) are
connected between OUT_+ and OUT_-, unless otherwise stated. TA= TMINto TMAX, unless otherwise noted. Typical values are at TA
MAX9708
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
ELECTRICAL CHARACTERISTICS (continued)(PVDD= VDD= +18V, PGND = GND = 0V, CSS= 0.47µF, CREG= 0.01µF, C1 = 0.1µF, C2 = 1µF, RLOAD = ∞, MONO = low (stereo
mode), SHDN= MUTE= high, G1 = low, G2 = high (AV= 22dB), FS1 = FS2 = high (SSM), SYNCIN = low. All load resistors (RL) are
connected between OUT_+ and OUT_-, unless otherwise stated. TA= TMINto TMAX, unless otherwise noted. Typical values are at TA
Note 1:All devices are 100% production tested at +25°C. All temperature limits are guaranteed by design.
Note 2:Inputs AC-coupled to GND.
Note 3:The device is current limited. The maximum output power is obtained with an 8Ωload.
Note 4:Testing performed with an 8Ωresistive load in series with a 68µH inductive load connected across BTL outputs. Mode tran-
sitions are controlled by SHDN.
MAX9708
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
Typical Operating Characteristics(PVDD= VDD= +18V, PGND = GND = 0V, CSS= 0.47µF, CREG= 0.01µF, C1 = 0.1µF, C2 = 1µF, RLOAD = ∞, SHDN= high, MONO
= low, MUTE= high, G1 = low, G2 = high, FS1 = FS2 = high (SSM), SYNCIN = low. All load resistors (RL) are between OUT_+ and
OUT_-, TA= +25°C, unless otherwise stated.)
MAX9708
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifierypical Operating Characteristics (continued)(PVDD= VDD= +18V, PGND = GND = 0V, CSS= 0.47µF, CREG= 0.01µF, C1 = 0.1µF, C2 = 1µF, RLOAD = ∞, SHDN= high, MONO
= low, MUTE= high, G1 = low, G2 = high, FS1 = FS2 = high (SSM), SYNCIN = low. All load resistors (RL) are between OUT_+ and
OUT_-, TA= +25°C, unless otherwise stated.)
MAX9708
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifierypical Operating Characteristics (continued)(PVDD= VDD= +18V, PGND = GND = 0V, CSS= 0.47µF, CREG= 0.01µF, C1 = 0.1µF, C2 = 1µF, RLOAD = ∞, SHDN= high, MONO
= low, MUTE= high, G1 = low, G2 = high, FS1 = FS2 = high (SSM), SYNCIN = low. All load resistors (RL) are between OUT_+ and
OUT_-, TA= +25°C, unless otherwise stated.)
MAX9708
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifierypical Operating Characteristics (continued)(PVDD= VDD= +18V, PGND = GND = 0V, CSS= 0.47µF, CREG= 0.01µF, C1 = 0.1µF, C2 = 1µF, RLOAD = ∞, SHDN= high, MONO
= low, MUTE= high, G1 = low, G2 = high, FS1 = FS2 = high (SSM), SYNCIN = low. All load resistors (RL) are between OUT_+ and
OUT_-, TA= +25°C, unless otherwise stated.)
Pin Description
MAX9708
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
Pin Description (continued)
MAX9708
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
Typical Application Circuits/Functional DiagramsFigure1. Typical Application and Functional Diagram in Stereo Mode
MAX9708
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifierypical Application Circuits/Functional Diagrams (continued)Figure2. Typical Application and Functional Diagram in Mono Mode
MAX9708
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
Detailed DescriptionThe MAX9708 filterless, Class D audio power amplifier
features several improvements to switch-mode amplifi-
er technology. The MAX9708 is a two-channel, stereo
amplifier with 21W output power on each channel. The
amplifier can be configured to output 42W output
power in mono mode. The device offers Class AB per-
formance with Class D efficiency, while occupying min-
imal board space. A unique filterless modulation
scheme and spread-spectrum switching mode create a
compact, flexible, low-noise, efficient audio power
amplifier. The differential input architecture reduces
common-mode noise pickup, and can be used without
input-coupling capacitors. The device can also be con-
figured as a single-ended input amplifier.
Mono/Stereo ConfigurationThe MAX9708 features a mono mode that allows the
right and left channels to operate in parallel, achieving
up to 42W of output power. The mono mode is enabled
by applying logic-high to MONO. In this mode, an
audio signal applied to the right channel (INR+/INR-) is
routed to the H-bridge of both channels, while a signal
applied to the left channel (INL+/INL-) is ignored.
OUTL+ must be connected to OUTR+ and OUTL- must
be connected to OUTR- using heavy PC board traces
as close to the device as possible (see Figure 2).
When the device is placed in mono mode on a PC
board with outputs wired together, ensure that the
MONO pin can never be driven low when the device is
enabled. Driving the MONO pin low (stereo mode)
while the outputs are wired together in mono mode may
trigger the short circuit or thermal protection or both,
and may even damage the device.
EfficiencyEfficiency of a Class D amplifier is attributed to the
region of operation of the output stage transistors. In a
Class D amplifier, the output transistors act as current-
steering switches and consume negligible additional
power. Any power loss associated with the Class D out-
put stage is mostly due to the I2R loss of the MOSFET
on-resistance and quiescent current overhead. The
theoretical best efficiency of a linear amplifier is 78%;
however, that efficiency is only exhibited at peak output
powers. Under normal operating levels (typical music
reproduction levels), efficiency falls below 30%, where-
as the MAX9708 still exhibits 87% efficiency under the
same conditions.
ShutdownThe MAX9708 features a shutdown mode that reduces
power consumption and extends battery life. DrivingSHDNlow places the device in low-power (0.1µA) shut-
down mode. Connect SHDNto digital high for normal
operation.
Mute FunctionThe MAX9708 features a clickless/popless mute mode.
When the device is muted, the outputs stop switching,
muting the speaker. Mute only affects the output stage
and does not shut down the device. To mute the
MAX9708, drive MUTEto logic-low. Driving MUTElow
during the power-up/down or shutdown/turn-on cycle
optimizes click-and-pop suppression.
Click-and-Pop SuppressionThe MAX9708 features comprehensive click-and-pop
suppression that eliminates audible transients on start-
up and shutdown. While in shutdown, the H-bridge is
pulled to GND through a 330kΩresistor. During startup
or power-up, the input amplifiers are muted and an
internal loop sets the modulator bias voltages to the
correct levels, preventing clicks and pops when the H-
bridge is subsequently enabled. Following startup, a
soft-start function gradually un-mutes the input ampli-
fiers. The value of the soft-start capacitor has an impact
on the click-and-pop levels as well as startup time.
Thermal SensorThe MAX9708 features an on-chip temperature sensor
that monitors the die temperature. When the junction
temperature exceeds a programmed level, TEMPis
pulled low. This flags the user to reduce power or shut
down the device. TEMPmay be connected to SS or
MUTEfor automatic shutdown during overheating. IfTEMPis connected to MUTE, during thermal-protection
mode, the audio is muted and the device is in mute
mode. If TEMPis connected to SS, during thermal-pro-
tection mode, the device is shut down but the thermal
sensor is still active.
