MAX9704ETJ ,15W / Filterless / Spread-Spectrum Mono/Stereo Class D AmplifiersFeaturesThe MAX9703/MAX9704 mono/stereo class D audio ♦ Filterless Class D Amplifierpower amplifier ..
MAX9704ETJ+ ,10W Stereo/15W Mono, Filterless, Spread-Spectrum, Class D AmplifiersElectrical Characteristics(V = 15V, AGND = PGND = 0V, SHDN ≥ V , A = 16dB, C = C = 0.47μF, C = 0.01 ..
MAX9704ETJ+T ,10W Stereo/15W Mono, Filterless, Spread-Spectrum, Class D AmplifiersBlock Diagrams0.47µFMAX9704INL+ OUTL+MAX9703H-BRIDGE0.47µFINL- OUTL-0.47µFIN+ OUT+H-BRIDGE0.47µF0.4 ..
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MAX9705BETB+ ,2.3W, Ultra-Low-EMI, Filterless, Class D Audio AmplifierELECTRICAL CHARACTERISTICS(V = PV = V = 3.3V, V = V = 0, SYNC = GND (FFM), R = ∞, R connected betwe ..
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MAX9704ETJ
15W / Filterless / Spread-Spectrum Mono/Stereo Class D Amplifiers
General DescriptionThe MAX9703/MAX9704 mono/stereo class D audio
power amplifiers provide class AB amplifier performance
with class D efficiency, conserving board space and
eliminating the need for a bulky heatsink. Using a class
D architecture, these devices deliver up to 15W while
offering up to 78% efficiency. Proprietary and patent-pro-
tected modulation and switching schemes render the tra-
ditional class D output filter unnecessary.
The MAX9703/MAX9704 offer two modulation schemes:
a fixed-frequency mode (FFM), and a spread-spectrum
mode (SSM) that reduces EMI-radiated emissions due
to the modulation frequency. The device utilizes a fully
differential architecture, a full bridged output, and com-
prehensive click-and-pop suppression.
The MAX9703/MAX9704 feature high 80dB PSRR, low
0.07% THD+N, and SNR in excess of 100dB. Short-cir-
cuit and thermal-overload protection prevent the
devices from being damaged during a fault condition.
The MAX9703 is available in a 32-pin TQFN (5mm x
5mm x 0.8mm) package. The MAX9704 is available in a
32-pin TQFN (7mm x 7mm x 0.8mm) package. Both
devices are specified over the extended -40°C to
+85°C temperature range.
Applications
FeaturesFilterless Class D AmplifierUnique Spread-Spectrum Mode Offers 5dB
Emissions Improvement Over Conventional
MethodsUp to 78% Efficient15W Output Power into 8ΩUp to 20W Peak PowerLow 0.07% THD+NHigh PSRR (80dB at 1kHz)10V to 25V Single-Supply OperationDifferential Inputs Minimize Common-Mode NoisePin-Selectable Gain Reduces Component CountIndustry-Leading Click-and-Pop SuppressionLow Quiescent Current (24mA)Low-Power Shutdown Mode (0.2µA)Short-Circuit and Thermal-Overload ProtectionAvailable in Thermally Efficient, Space-Saving
Packages
32-Pin TQFN (5mm x 5mm x 0.8mm)–MAX9703
32-Pin TQFN (7mm x 7mm x 0.8mm)–MAX9704
MAX9703/MAX9704
15W, Filterless, Spread-Spectrum
Mono/Stereo Class D Amplifiers19-3160; Rev 1; 3/04
Ordering Information*EP = Exposed paddle.
LCD TVs
LCD Monitors
Desktop PCs
LCD Projectors
Hands-Free Car
Phone Adaptors
Automotive
Pin Configurations appear at end of data sheet.
Block Diagrams
MAX9703/MAX9704
15W, Filterless, Spread-Spectrum
Mono/Stereo Class D Amplifiers
ABSOLUTE MAXIMUM RATINGSStresses 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.
(All voltages referenced to GND.)
VDDto PGND, AGND.............................................................30V
OUTR_, OUTL_, C1N..................................-0.3V to (VDD+ 0.3V)
C1P............................................(VDD- 0.3V) to (CHOLD + 0.3V)
CHOLD........................................................(VDD- 0.3V) to +40V
All Other Pins to GND.............................................-0.3V to +12V
Duration of OUTR_/OUTL_
Short Circuit to GND, VDD..................................................10s
Continuous Input Current (VDD, PGND)...............................1.6A
Continuous Input Current......................................................0.8A
Continuous Input Current (all other pins)..........................±20mA
Continuous Power Dissipation (TA= +70°C)
MAX9703 32-Pin TQFN (derate 21.3mW/°C
above +70°C)..........................................................1702.1mW
MAX9704 32-Pin TQFN (derate 33.3mW/°C
above +70°C)..........................................................2666.7mW
Junction Temperature......................................................+150°C
Operating Temperature Range...........................-40°C to +85°C
Storage Temperature Range.............................-65°C to +150°C
Lead Temperature (soldering, 10s).................................+300°C
ELECTRICAL CHARACTERISTICS(VDD= 15V, GND = PGND = 0V, SHDN≥VIH, AV= 16dB, CSS= CIN= CREG= 0.47µF, C1 = 100nF, C2 = 1µF, FS1 = FS2 = GND
(fS= 660kHz), RLconnected between OUTL+ and OUTL- and OUTR+ and OUTR-, TA= TMINto TMAX, unless otherwise noted.
MAX9703/MAX9704
15W, Filterless, Spread-Spectrum
Mono/Stereo Class D Amplifiers
ELECTRICAL CHARACTERISTICS (continued)(VDD= 15V, GND = PGND = 0V, SHDN≥VIH, AV= 16dB, CSS= CIN= CREG= 0.47µF, C1 = 100nF, C2 = 1µF, FS1 = FS2 = GND
(fS= 660kHz), RLconnected between OUTL+ and OUTL- and OUTR+ and OUTR-, TA= TMINto TMAX, unless otherwise noted.
Note 1:All devices are 100% production tested at +25°C. All temperature limits are guaranteed by design.
Note 2:Testing performed with a resistive load in series with an inductor to simulate an actual speaker load. For RL= 8Ω, L = 68µH.
For RL= 4Ω, L = 33µH.
Note 3:PSRR is specified with the amplifier inputs connected to GND through CIN.
Note 4:Do not apply more than 8V to any logic pin.
MAX9703/MAX9704
15W, Filterless, Spread-Spectrum
Mono/Stereo Class D Amplifiers
Typical Operating Characteristics(33µH with 4Ω, 68µH with 8Ω, part in SSM mode, 136µH with 16Ω, measurement BW = 22Hz to 22kHz, unless otherwise noted.)
MAX9703/MAX9704
15W, Filterless, Spread-Spectrum
Mono/Stereo Class D Amplifiers
Typical Operating Characteristics (continued)(33µH with 4Ω, 68µH with 8Ω, part in SSM mode, 136µH with 16Ω, measurement BW = 22Hz to 22kHz, unless otherwise noted.)
MAX9703/MAX9704
15W, Filterless, Spread-Spectrum
Mono/Stereo Class D Amplifiers
Typical Operating Characteristics (continued)(33µH with 4Ω, 68µH with 8Ω, part in SSM mode, 136µH with 16Ω, measurement BW = 22Hz to 22kHz, unless otherwise noted.)
MAX9703/MAX9704
15W, Filterless, Spread-Spectrum
Mono/Stereo Class D Amplifiers
MAX9703/MAX9704
Detailed DescriptionThe MAX9703/MAX9704 filterless, class D audio power
amplifiers feature several improvements to switch-
mode amplifier technology. The MAX9703 is a mono
amplifier, the MAX9704 is a stereo amplifier. These
devices offer class AB performance with class D effi-
ciency, while occupying minimal board space. A
unique filterless modulation scheme and spread-spec-
trum switching mode create a compact, flexible, low-
noise, efficient audio power amplifier. The differential
input architecture reduces common-mode noise pick-
up, and can be used without input-coupling capacitors.
The devices can also be configured as a single-ended
input amplifier.
Comparators monitor the device inputs and compare
the complementary input voltages to the triangle wave-
form. The comparators trip when the input magnitude of
the triangle exceeds their corresponding input voltage.
Operating Modes
Fixed-Frequency Modulation (FFM) ModeThe MAX9703/MAX9704 feature three FFM modes with
different switching frequencies (Table 1). In FFM mode,
the frequency spectrum of the class D output consists
of the fundamental switching frequency and its associ-
ated harmonics (see the Wideband FFT graph in the
Typical Operating Characteristics). The MAX9703/
MAX9704 allow the switching frequency to be changed
by ±35%, should the frequency of one or more of the
harmonics fall in a sensitive band. This can be done at
any time and does not affect audio reproduction.
Spread-Spectrum Modulation (SSM) ModeThe MAX9703/MAX9704 feature a unique, patented
spread-spectrum mode that flattens the wideband
spectral components, improving EMI emissions that
may be radiated by the speaker and cables. This mode
is enabled by setting FS1 = FS2 = H. In SSM mode, the
switching frequency varies randomly by ±7% around
the center frequency (670kHz). The modulation scheme
remains the same, but the period of the triangle wave-
form changes from cycle to cycle. Instead of a large
amount of spectral energy present at multiples of the
switching frequency, the energy is now spread over a
bandwidth that increases with frequency. Above a few
megahertz, the wideband spectrum looks like white
noise for EMI purposes.
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 I*R 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%,
whereas the MAX9704 still exhibits >78% efficiency
under the same conditions (Figure 2).
15W, Filterless, Spread-Spectrum
Mono/Stereo Class D Amplifiers
ShutdownThe MAX9703/MAX9704 have a shutdown mode that
reduces power consumption and extends battery life.
Driving SHDNlow places the device in low-power
(0.2µA) shutdown mode. Connect SHDNto a logic high
for normal operation.
Click-and-Pop SuppressionThe MAX9703/MAX9704 feature comprehensive click-
and-pop suppression that eliminates audible transients
on startup and shutdown. While in shutdown, the H-
bridge is pulled to GND through 330kΩ. During startup,
or power-up, the input amplifiers are muted and an inter-
nal 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 unmutes the input amplifiers. The
value of the soft-start capacitor has an impact on the
click/pop levels. For optimum performance, CSS should
be at least 180nF with a voltage rating of at least 7V.
Applications Information
Filterless OperationTraditional class D amplifiers require an output filter to
recover the audio signal from the amplifier’s PWM out-
put. The filters add cost, increase the solution size of
the amplifier, and can decrease efficiency. The tradi-
tional PWM scheme uses large differential output
swings (2 ✕VDDpeak-to-peak) and causes large ripple
currents. Any parasitic resistance in the filter compo-
nents results in a loss of power, lowering the efficiency.
The MAX9703/MAX9704 do not require an output filter.
The devices rely on the inherent inductance of the
speaker coil and the natural filtering of both the speak-
er and the human ear to recover the audio component
of the square-wave output. Eliminating the output filter
results in a smaller, less-costly, more-efficient solution.
Because the frequency of the MAX9703/MAX9704 out-
put is well beyond the bandwidth of most speakers,
voice coil movement due to the square-wave frequency
is very small. Although this movement is small, a speak-
er not designed to handle the additional power can be
damaged. For optimum results, use a speaker with a
series inductance > 30µH. Typical 8Ωspeakers exhibit
series inductances in the range of 30µH to 100µH.
Optimum efficiency is achieved with speaker induc-
tances > 60µH.
Gain SelectionTable 2shows the suggested gain settings to attain a
maximum output power from a given peak input voltage
and given load.
Output OffsetUnlike a class AB amplifier, the output offset voltage of
class D amplifiers does not noticeably increase quies-
cent current draw when a load is applied. This is due to
the power conversion of the class D amplifier. For
example, an 8mVDC offset across an 8Ωload results in
1mA extra current consumption in a class AB device. In
the class D case, an 8mV offset into 8Ωequates
to an additional power drain of 8µW. Due to the high
efficiency of the class D amplifier, this represents an
additional quiescent current draw of: 8µW/(VDD/100 ✕η),
which is in the order of a few microamps.
MAX9703/MAX9704
15W, Filterless, Spread-Spectrum
Mono/Stereo Class D Amplifiers
