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MAX9750AETIMAXIMN/a3avai2.6W Stereo Audio Power Amplifiers and DirectDrive Headphone Amplifiers
MAX9750CETIMAXIMN/a15avai2.6W Stereo Audio Power Amplifiers and DirectDrive Headphone Amplifiers
MAX9755ETIMAXIMN/a11avai2.6W Stereo Audio Power Amplifiers and DirectDrive Headphone Amplifiers


MAX9750CETI ,2.6W Stereo Audio Power Amplifiers and DirectDrive Headphone Amplifiersfeatures a 2:1 input multiplexer,♦ Low-Power Shutdown Modeallowing multiple audio sources to be sel ..
MAX9750CETI+ ,2.6W Stereo Audio Power Amplifiers and DirectDrive® Headphone AmplifiersBlock Diagrams continued at end of data sheet.____ Maxim Integrated Products 1For pricing, delivery ..
MAX9750CETI+ ,2.6W Stereo Audio Power Amplifiers and DirectDrive® Headphone AmplifiersApplications♦ ±8kV ESD-Protected Headphone Driver OutputsNotebook PCs Flat-Panel TVs♦ Available in ..
MAX9750CETI+C2U ,2.6W Stereo Audio Power Amplifiers and DirectDrive® Headphone AmplifiersBlock Diagrams continued at end of data sheet.____ Maxim Integrated Products 1For pricing, delivery ..
MAX9750CETI+T ,2.6W Stereo Audio Power Amplifiers and DirectDrive® Headphone AmplifiersFeaturesThe MAX9750/MAX9751/MAX9755 combine a stereo,♦ No DC-Blocking Capacitors Required—Provides® ..
MAX9752BETI+T ,2.2W, Low-EMI, Stereo, Class D Power Amplifiers with DirectDrive Headphone AmplifiersBlock DiagramsMAX9752 MAX9753 MAX9754SCLASS CLASS CLASSD D DSAMP AMP AMPVOLINPUT HPS HPS HPSMUX SEL ..
MB89475 ,F2MC-8L/Low Power/Low Voltage Microcontrollersapplications forconsumer product.2* : F MC stands for FUJITSU Flexible Microcontroller.n
MB89535A ,F2MC-8L/Low Power/Low Voltage MicrocontrollersFEATURES• Wide range of package options• Two types of QFP packages (1 mm pitch, 0.65 mm pitch) • LQ ..
MB89535A ,F2MC-8L/Low Power/Low Voltage MicrocontrollersFUJITSU SEMICONDUCTORDS07-12547-4EDATA SHEET8-bit Original Microcontroller CMOS2F MC-8L MB89530A Se ..
MB89537A , 8-bit Original Microcontroller CMOS, F-2MC-8L MB89530A Series
MB89537A , 8-bit Original Microcontroller CMOS, F-2MC-8L MB89530A Series
MB89537AC , 8-bit Original Microcontroller CMOS, F-2MC-8L MB89530A Series


MAX9750AETI-MAX9750CETI-MAX9755ETI
2.6W Stereo Audio Power Amplifiers and DirectDrive Headphone Amplifiers
General Description
The MAX9750/MAX9751/MAX9755 combine a stereo,
2.6W audio power amplifier and stereo DirectDrive
110mW headphone amplifier in a single device. The
headphone amplifier uses Maxim’s patented DirectDrive
architecture that produces a ground-referenced output
from a single supply, eliminating the need for large DC-
blocking capacitors, saving cost, space, and component
height. A high 90dB PSRR and low 0.01% THD+N
ensures clean, low-distortion amplification of the audio
signal.
The MAX9750 features an analog volume control, and a
BEEP input. The MAX9751 features a 2:1 input multiplexer,
allowing multiple audio sources to be selected. All devices
feature a single-supply voltage, a shutdown mode, logic-
selectable gain, and a headphone sense input. Industry-
leading click-and-pop suppression eliminates audible
transients during power and shutdown cycles.
The MAX9750/MAX9751/MAX9755 are offered in space-
saving, thermally efficient 28-pin thin QFN (5mm x 5mm
x 0.8mm) and 28-pin TSSOP-EP packages. Both devices
have thermal-overload and output short-circuit protec-
tion, and are specified over the extended -40°C to +85°C
temperature range.
Applications

Notebook PCsFlat-Panel TVs
Tablet PCsPC Displays
Portable DVDLCD Projectors
Features
No DC-Blocking Capacitors Required—Provides
Industry’s Most Compact Notebook Audio
Solution
PC2001 Compliant5V Single-Supply OperationClass AB 2.6W Stereo BTL Speaker Amplifiers110mW DirectDrive Headphone AmplifiersHigh 90dB PSRRLow-Power Shutdown ModeIndustry-Leading Click-and-Pop SuppressionLow 0.01% THD+N at 1kHzShort-Circuit and Thermal ProtectionSelectable Gain Settings Analog Volume Control (MAX9750)Beep Input with Glitch Filter (MAX9750)2:1 Stereo Input MUX (MAX9751)±8kV ESD-Protected Headphone Driver OutputsAvailable in Space-Saving, Thermally Efficient
Packages
28-Pin Thin QFN (5mm x 5mm x 0.8mm)
28-Pin TSSOP-EP
MAX9750/MAX9751/MAX9755
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
Ordering Information

19-3006; Rev 0; 1/04
*Future product—contact factory for availability.
**EP = Exposed Paddle.Lead-free package.
Simplified Block Diagrams
MAX9750/MAX9751/MAX9755
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
ABSOLUTE MAXIMUM RATINGS

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 (VDD, PVDD, HPVDD, CPVDDto GND)..........+6V
GND to PGND.....................................................................±0.3V
CPVSS, C1N, VSSto GND.........................-6.0V to (GND + 0.3V)
HPOUT_ to GND....................................................................±3V
Any Other Pin.............................................-0.3V to (VDD+ 0.3V)
Duration of OUT_ Short Circuit to GND or PVDD........Continuous
Duration of OUT_+ Short Circuit to OUT_-.................Continuous
Duration of HPOUT_ Short Circuit to GND,
VSSor HPVDD.........................................................Continuous
Continuous Current (PVDD, OUT_, PGND)...........................1.7A
Continuous Current (CPVDD, C1N, C1P, CPVSS, VSS, HPVDD,
HPOUT_).......................................................................850mA
Continuous Input Current (All Other Pins)........................±20mA
Continuous Power Dissipation (TA= +70°C)
28-Pin Thin QFN (derate 20.8mW/°C above +70°C)..1667mW
28-Pin TSSOP-EP (derate 23.8mW/°C above +70°C).1904mW
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= PVDD= CPVDD= HPVDD= 5V, GND = PGND = CPGND = 0V, SHDN= VDD, CBIAS= 1µF, C1 = C2 = 1µF, speaker load ter-
minated between OUT_+ and OUT_-, headphone load terminated between HPOUT_ and GND, MAX9750: GAIN1 = GAIN2 = VOL == 33kΩ= GND, MAX9751/MAX9755: GAIN = VDD= IN1/2= GND, TA= TMINto TMAX, unless otherwise noted. Typical values are
MAX9750/MAX9751/MAX9755
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
ELECTRICAL CHARACTERISTICS (continued)

(VDD= PVDD= CPVDD= HPVDD= 5V, GND = PGND = CPGND = 0V, SHDN= VDD, CBIAS= 1µF, C1 = C2 = 1µF, speaker load ter-
minated between OUT_+ and OUT_-, headphone load terminated between HPOUT_ and GND, MAX9750: GAIN1 = GAIN2 = VOL == 33kΩ= GND, MAX9751/MAX9755: GAIN = VDD= IN1/2= GND, TA= TMINto TMAX, unless otherwise noted. Typical values are
MAX9750/MAX9751/MAX9755
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
ELECTRICAL CHARACTERISTICS (continued)

(VDD= PVDD= CPVDD= HPVDD= 5V, GND = PGND = CPGND = 0V, SHDN= VDD, CBIAS= 1µF, C1 = C2 = 1µF, speaker load ter-
minated between OUT_+ and OUT_-, headphone load terminated between HPOUT_ and GND, MAX9750: GAIN1 = GAIN2 = VOL == 33kΩ= GND, MAX9751/MAX9755: GAIN = VDD= IN1/2= GND, TA= TMINto TMAX, unless otherwise noted. Typical values are
MAX9750/MAX9751/MAX9755
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
ELECTRICAL CHARACTERISTICS (continued)

(VDD= PVDD= CPVDD= HPVDD= 5V, GND = PGND = CPGND = 0V, SHDN= VDD, CBIAS= 1µF, C1 = C2 = 1µF, speaker load ter-
minated between OUT_+ and OUT_-, headphone load terminated between HPOUT_ and GND, MAX9750: GAIN1 = GAIN2 = VOL == 33kΩ= GND, MAX9751/MAX9755: GAIN = VDD= IN1/2= GND, TA= TMINto TMAX, unless otherwise noted. Typical values are
Note 2:
Guaranteed by design. Not production tested.
Note 3:
PSRR is specified with the amplifier input connected to GND through CIN.
Note 4:
See Table 3 for details of the mute levels.
Note 5:
The value of RBdictates the minimum beep signal amplitude (see the Beep Inputsection).
MAX9750/MAX9751/MAX9755
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
Typical Operating Characteristics

(Measurement BW = 22Hz to 22kHz, TA = +25°C, unless otherwise noted.)
Typical Operating Characteristics (continued)
(Measurement BW = 22Hz to 22kHz, TA = +25°C, unless otherwise noted.)
MAX9750/MAX9751/MAX9755
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
ypical Operating Characteristics (continued)(Measurement BW = 22Hz to 22kHz, TA = +25°C, unless otherwise noted.)
MAX9750/MAX9751/MAX9755
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
MAX9750/MAX9751/MAX9755
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiersypical Operating Characteristics (continued)

(Measurement BW = 22Hz to 22kHz, TA = +25°C, unless otherwise noted.)
MAX9750/MAX9751/MAX9755
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
MAX9750/MAX9751/MAX9755
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
Detailed Description

The MAX9750/MAX9751/MAX9755 combine a 2.6W BTL
speaker amplifier and a 110mW DirectDrive headphone
amplifier with integrated headphone sensing and com-
prehensive click-and-pop suppression. The MAX9750
features an analog volume control, BEEP input, and
four-level gain control. The MAX9751 features a 2:1
input stereo multiplexer and two-level gain control. All
devices feature high 90dB PSRR, low 0.01% THD+N,
industry-leading click-pop performance, and a low-
power shutdown mode.
Each signal path consists of an input amplifier that sets
the gain of the signal path and feeds both the speaker
and headphone amplifier (Figure1). The speaker
amplifier uses a BTL architecture, doubling the voltage
drive to the speakers and eliminating the need for DC-
blocking capacitors. The output consists of two signals,
identical in magnitude, but 180°out of phase.
The headphone amplifiers use Maxim’s patented
DirectDrive architecture that eliminates the bulky output
DC-blocking capacitors required by traditional head-
phone amplifiers. A charge pump inverts the positive
supply (CPVDD), creating a negative supply (CPVSS).
The headphone amplifiers operate from these bipolar
supplies with their outputs biased about GND (Figure2).
The amplifiers have almost twice the supply range
compared to other single-supply amplifiers, nearly qua-
drupling the available output power. The benefit of the
GND bias is that the amplifier outputs no longer have a
DC component (typically VDD / 2). This eliminates the
large DC-blocking capacitors required with convention-
al headphone amplifiers, conserving board space and
system cost, and improving frequency response.
The MAX9750 features an analog volume control that
varies the gain of the amplifiers based on the DC volt-
age applied at VOL. Both devices feature an undervolt-
age lockout that prevents operation from an insufficient
power supply and click-and-pop suppression that elim-
inates audible transients on startup and shutdown. The
amplifiers include thermal-overload and short-circuit
protection, and can withstand ±8kV ESD strikes on the
headphone amplifier outputs (IEC air discharge). An
additional feature of the speaker amplifiers is that there
is no phase inversion from input to output.
DirectDrive

Conventional single-supply headphone amplifiers have
their outputs biased about a nominal DC voltage (typi-
cally half the supply) for maximum dynamic range.
Large coupling capacitors are needed to block this DC
bias from the headphones. Without these capacitors, a
Figure1. MAX9750/MAX9751 Signal Path
Figure2. Traditional Headphone Amplifier Output Waveform
vs. DirectDrive Headphone Amplifier Output Waveform
MAX9750/MAX9751/MAX9755
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers

significant amount of DC current flows to the headphone,
resulting in unnecessary power dissipation and possible
damage to both headphone and headphone amplifier.
Maxim’s patented DirectDrive architecture uses a charge
pump to create an internal negative supply voltage. This
allows the MAX9750/MAX9751/MAX9755 headphone
amplifier output to be biased about GND, almost dou-
bling the dynamic range while operating from a single
supply. With no DC component, there is no need for the
large DC-blocking capacitors. Instead of two large
capacitors (220µF typ), the MAX9750/MAX9751/
MAX9755 charge pump requires only two small ceramic
capacitors (1µF typ), conserving board space, reducing
cost, and improving the frequency response of the head-
phone amplifier. See the Output Power vs. Charge-Pump
Capacitance and Load Resistance graph in the Typical
Operating Characteristicsfor details of the possible
capacitor values.
Previous attempts to eliminate the output coupling
capacitors involved biasing the headphone return
(sleeve) to the DC bias voltage of the headphone
amplifiers. This method raised some issues:The sleeve is typically grounded to the chassis. Using
this biasing approach, the sleeve must be isolated
from system ground, complicating product design.During an ESD strike, the amplifier’s ESD structures
are the only path to system ground. The amplifier
must be able to withstand the full ESD strike.When using the headphone jack as a lineout to other
equipment, the bias voltage on the sleeve may con-
flict with the ground potential from other equipment,
resulting in large ground-loop current and possible
damage to the amplifiers.
Low-Frequency Response

In addition to the cost and size disadvantages, the DC-
blocking capacitors limit the low-frequency response of
the amplifier and distort the audio signal:The impedance of the headphone load to the DC-
blocking capacitor forms a highpass filter with the
-3dB point determined by:
where RLis the impedance of the headphone and
COUTis the value of the DC-blocking capacitor.
The highpass filter is required by conventional sin-
gle-ended, single-supply headphone amplifiers to
block the midrail DC component of the audio signal
from the headphones. Depending on the -3dB point,
the filter can attenuate low-frequency signals within
the audio band. Larger values of COUTreduce the
attenuation but are physically larger, more expen-
sive capacitors. Figure3 shows the relationship
between the size of COUTand the resulting low-fre-
quency attenuation. Note that the -3dB point for a
16Ωheadphone with a 100µF blocking capacitor is
100Hz, well within the audio band.The voltage coefficient of the capacitor, the change
in capacitance due to a change in the voltage
across the capacitor, distorts the audio signal. At
frequencies around the -3dB point, the reactance of
the capacitor dominates, and the voltage coefficient
appears as frequency-dependent distortion. Figure
4 shows the THD+N introduced by two different
capacitor dielectrics. Note that around the -3dB
point, THD+N increases dramatically.
The combination of low-frequency attenuation and fre-
quency-dependent distortion compromises audio
reproduction. DirectDrive improves low-frequency
reproduction in portable audio equipment that empha-
sizes low-frequency effects such as multimedia lap-
tops, and MP3, CD, and DVD players.
Charge Pump

The MAX9750/MAX9751/MAX9755 feature a low-noise
charge pump. The 550kHz switching frequency is well
beyond the audio range, and does not interfere with the
audio signals. The switch drivers feature a controlled
switching speed that minimizes noise generated by turn-
on and turn-off transients. Limiting the switching speed of
the charge pump minimizes the di/dt noise caused by the
MAX9750/MAX9751/MAX9755
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers

parasitic bond wire and trace inductance. Although not
typically required, additional high-frequency ripple atten-
uation can be achieved by increasing the size of C2 (see
the Typical Application Circuit).
Headphone Sense Input (HPS)

The headphone sense input (HPS) monitors the head-
phone jack and automatically configures the device
based upon the voltage applied at HPS. A voltage of
less than 0.8V sets the device to speaker mode. A volt-
age of greater than 2V disables the bridge amplifiers
and enables the headphone amplifiers.
For automatic headphone detection, connect HPS to the
control pin of a 3-wire headphone jack as shown in
Figure5. With no headphone present, the output imped-
ance of the headphone amplifier pulls HPS low. When a
headphone plug is inserted into the jack, the control pin
is disconnected from the tip contact and HPS is pulled
to VDDthrough a 10µA current source.
BIAS

The MAX9750/MAX9751/MAX9755 feature an internally
generated, power-supply independent, common-mode
bias voltage of 1.8V referenced to GND. BIAS provides
both click-and-pop suppression and sets the DC bias
level for the amplifiers. Choose the value of the bypass
capacitor as described in the BIAS Capacitorsection.
No external load should be applied to BIAS. Any load
lowers the BIAS voltage, affecting the overall perfor-
mance of the device.
Gain Selection
MAX9750

The MAX9750 features an internally set, selectable gain.
The GAIN1 and GAIN2 inputs set the maximum gain of
the MAX9750 speaker and headphone amplifiers (Table
1). The gain of the device can vary based upon the volt-
age at VOL (see the Analog Volume Controlsection).
However, the maximum gain cannot be exceeded.
MAX9751/MAX9755

The gain of the MAX9751/MAX9755 is set by the GAIN
input. Driving GAIN high sets the gain of the speaker
amplifiers to 9dB and the gain of the headphone ampli-
fiers to 0dB. Driving GAIN low sets the gain of the
speaker amplifiers to 10.5dB, and the gain of the head-
phone amplifiers to 3dB (Table2).
Analog Volume Control (VOL)

The MAX9750 features an analog volume control that
varies the gain of the device in 31 discrete steps based
upon the DC voltage applied to VOL. The input range of
VVOLis from 0 (full volume) to 0.858 x HPVDD(full mute),
with example step sizes shown in Table3. Connect the
reference of the device driving VOL (Figure6) to HPVDD.
Since the volume control ADC is ratiometric to HPVDD,
any changes in HPVDDare negated. The gain step sizes
are not constant; the step sizes are 0.5dB/step at the
upper extreme, 2dB/step in the midrange, and 4dB/step
at the lower extreme. Figure7 shows the transfer function
of the volume control for a 3.3V supply.
MAX9750/MAX9751/MAX9755
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
BEEP Input

The MAX9750 features an audible alert beep input
(BEEP) that accepts a mono system alert signal and
mixes it into the stereo audio path. When the amplitude
of VBEEP(OUT)exceeds 800mVP-P(Figure 8) and the
frequency of the beep signal is greater than 300Hz, the
beep signal is mixed into the active audio path (speaker
or headphone). If the signal at VBEEP(OUT)is either
<800mVP-Por <300Hz, the BEEP signal is not mixed into
the audio path. The amplitude of the BEEP signal at the
device output is roughly the amplitude of VBEEP(OUT)
times the gain of the selected signal path.
The input resistor (RB) sets the gain of the BEEP input
amplifier, and thus the amplitude of VBEEP(OUT). Choosebased on:
where RINTis the value of the BEEP amplifier feedback
resistor (47kΩ) and VINis the BEEP input amplitude.
Note that the BEEP amplifier can be set up as either an
attenuator, if the original alert signal amplitude is too
large, or set to gain up the alert signal if it is below
800mVP-P. AC couple the alert signal to BEEP. Choose
the value of the coupling capacitor as described in the
Input Filteringsection. Multiple beep inputs can be
summed (Figure 8).
Input Multiplexer

The MAX9751 features a 2:1 input multiplexer on each
amplifier, allowing input selection between two stereo
sources. The logic input IN1/2controls both multiplex-
ers. A logic high selects input IN_1 and a logic low
selects input IN_2.
Shutdown

The MAX9750/MAX9751/MAX9755 features a 0.2µA,
low-power shutdown mode that reduces quiescent cur-
rent consumption and extends battery life. Driving
SHDNlow disables the drive amplifiers, bias circuitry,
and charge pump, and drives BIAS and all outputs to
GND. Connect SHDNto VDDfor normal operation.
Click-and-Pop Suppression
Speaker Amplifier

The MAX9750/MAX9751/MAX9755 speaker amplifiers
feature Maxim’s comprehensive, industry-leading click-
and-pop suppression. During startup, the click-pop
suppression circuitry eliminates any audible transient
sources internal to the device. When entering shut-
down, both amplifier outputs ramp to GND quickly and
simultaneously.
MAX9750/MAX9751/MAX9755
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
Table 3a. MAX9750A Volume Levels

X = Don’t care.
MAX9750/MAX9751/MAX9755
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
Table 3B. MAX9750B Volume Levels

X = Don’t care.
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