MAX9705AETB+ ,2.3W, Ultra-Low-EMI, Filterless, Class D Audio AmplifierFeatures♦ Filterless Amplifier Passes FCC-RadiatedThe MAX9705 3rd-generation, ultra-low EMI, mono, ..
MAX9705AETB+T ,2.3W, Ultra-Low-EMI, Filterless, Class D Audio AmplifierApplicationsEMI Spectrum DiagramCellular Phones MP3 PlayersPDAs Portable Audio50.045.040.0FCC EMI L ..
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 ..
MAX9705BETB+T ,2.3W, Ultra-Low-EMI, Filterless, Class D Audio AmplifierELECTRICAL CHARACTERISTICS (continued)(V = PV = V = 3.3V, V = V = 0, SYNC = GND (FFM), R = ∞, R con ..
MAX9705BETB+TC4S ,2.3W, Ultra-Low-EMI, Filterless, Class D Audio AmplifierMAX970519-3405; Rev 3; 5/092.3W, Ultra-Low-EMI, Filterless, Class D Audio Amplifier
MAX9705CEBC+T ,2.3W, Ultra-Low-EMI, Filterless, Class D Audio AmplifierFeatures♦ Filterless Amplifier Passes FCC-RadiatedThe MAX9705 3rd-generation, ultra-low EMI, mono, ..
MB89165A ,8-bit Proprietary MicrocontrollerFUJITSU SEMICONDUCTORDS07-12405-2EDATA SHEET8-bit Proprietary MicrocontrollerCMOS2F MC-8L MB89160/1 ..
MB89185 ,F2MC-8L/Low Power/Low Voltage MicrocontrollersFUJITSU SEMICONDUCTORDS07-12404-2EDATA SHEET8-bit Proprietary MicrocontrollerCMOS2F MC-8L MB89180 S ..
MB89191A ,8-bit Proprietary MicrocontrollerFUJITSU SEMICONDUCTORDS07-12512-7EDATA SHEET8-bit Proprietary MicrocontrollerCMOS2F MC-8L MB89190/1 ..
MB89191A ,8-bit Proprietary MicrocontrollerFUJITSU SEMICONDUCTORDS07-12512-7EDATA SHEET8-bit Proprietary MicrocontrollerCMOS2F MC-8L MB89190/1 ..
MB89191A ,8-bit Proprietary MicrocontrollerFEATURES • Minimum execution time: 0.95 m s at 4.2 MHz (VCC = 2.7 V) 2•F MC-8L family CPU core•Two ..
MB89191PF ,8-bit Proprietary MicrocontrollerFUJITSU SEMICONDUCTORDS07-12512-7EDATA SHEET8-bit Proprietary MicrocontrollerCMOS2F MC-8L MB89190/1 ..
MAX9705AETB+-MAX9705AETB+T-MAX9705BETB+-MAX9705BETB+T-MAX9705BETB+TC4S-MAX9705CEBC+T-MAX9705DETB+T
2.3W, Ultra-Low-EMI, Filterless, Class D Audio Amplifier
General DescriptionThe MAX9705 3rd-generation, ultra-low EMI, mono, Class
D audio power amplifier provides Class AB performance
with Class D efficiency. The MAX9705 delivers 2.3W into
a 4Ωload and offers efficiencies above 85%. Active
emissions limiting (AEL) circuitry greatly reduces EMI by
actively controlling the output FET gate transitions under
all possible transient output-voltage conditions. AEL pre-
vents high-frequency emissions resulting from conven-
tional Class D free-wheeling behavior in the presence of
an inductive load. Zero dead time (ZDT) technology
maintains state-of-the-art efficiency and THD+N perfor-
mance by allowing the output FETs to switch simultane-
ously without cross-conduction. A spread-spectrum
modulation scheme eliminates the need for output filter-
ing found in traditional Class D devices. These design
concepts reduce an application’s component count and
extend battery life.
The MAX9705 offers two modulation schemes: a fixed-
frequency (FFM) mode and a spread-spectrum (SSM)
mode that further reduces EMI-radiated emissions due to
the modulation frequency. The MAX9705 oscillator can
be synchronized to an external clock through the SYNC
input, allowing the switching frequency to be externally
defined. The SYNC input also allows multiple MAX9705s
to be cascaded and frequency locked, minimizing inter-
ference due to clock intermodulation. The device utilizes
a fully differential architecture, a full-bridged output, and
comprehensive click-and-pop suppression. The gain of
the MAX9705 is set internally (MAX9705A: 6dB,
MAX9705B: 12dB, MAX9705C: 15.6dB, MAX9705D:
20dB), further reducing external component count.
The MAX9705 is available in 10-pin TDFN (3mm x 3mm x
0.8mm), and 12-bump UCSP™ (1.5mm x 2mm x0.6mm)
packages. The MAX9705 is specified over the extended
-40°C to +85°C temperature range.
Applications
FeaturesFilterless Amplifier Passes FCC-Radiated
Emissions Standards with 24in of CableUnique Spread-Spectrum Mode and Active
Emissions Limiting (AEL) Achieves Better than
20dB Margin Under FCC LimitsZero Dead Time (ZDT) H-Bridge Maintains State-
of-the-Art Efficiency and THD+NSimple Master-Slave Setup for Stereo OperationUp to 90% Efficiency2.3W into 4Ω(1% THD+N)Low 0.02% THD+N (POUT= 1W, VDD= 5.0V)High PSRR (75dB at 217Hz)Integrated Click-and-Pop SuppressionLow Quiescent Current (5.4mA)Low-Power Shutdown Mode (0.3µA)Short-Circuit and Thermal-Overload ProtectionAvailable in Thermally Efficient, Space-Saving
Packages
10-Pin TDFN (3mm x 3mm x 0.8mm)
12-Bump UCSP (1.5mm x 2mm x 0.6mm)Pin-for-Pin Compatible with the MAX9700 and
MAX9712
MAX9705
2.3W, Ultra-Low-EMI, Filterless,
Class D Audio Amplifier
Ordering Information19-3405; Rev 3; 5/09
EVALUATION KIT
AVAILABLECellular Phones
PDAs
MP3 Players
Portable Audio
PARTTEMP RANGEPIN-
PACKAGE
TOP
MARKMAX9705AETB+T-40oC to +85oC10 TDFNACY
MAX9705AEBC+T-40oC to +85oC12 UCSPACH
MAX9705BETB+T-40oC to +85oC10 TDFNACX
MAX9705BEBC+T-40oC to +85oC12 UCSPACG
Ordering Information continued at end of data sheet.UCSP is a trademark of Maxim Integrated Products, Inc.
+Denotes a lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
Selector Guide appears at end of data sheet.FREQUENCY (MHz)
AMPLITUDE (dB
V/m)FCC EMI LIMIT
MAXIM'S NEW ULTRA-LOW
OUTPUT SPECTRUM
EMI Spectrum Diagram
2.3W, Ultra-Low-EMI, Filterless,
Class D Audio Amplifier
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS(VDD
= PVDD= VSHDN= 3.3V, VGND= VPGND= 0, SYNC = GND (FFM), RL= ∞, RLconnected between OUT+ and OUT-,= TMINto TMAX, unless otherwise noted. Typical values are at TA= +25°C.) (Notes 1, 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.
VDDto GND..............................................................................6V
PVDDto PGND.........................................................................6V
GND to PGND.......................................................-0.3V to +0.3V
PVDDto VDD..........................................................-0.3V to +0.3V
All Other Pins to GND.................................-0.3V to (VDD+ 0.3V)
Continuous Current Into/Out of PVDD/PGND/OUT_........±600mA
Continuous Input Current (all other pins).........................±20mA
Duration of OUT_ Short Circuit to GND or PVDD........Continuous
Duration of Short Circuit Between OUT+ and OUT-.....Continuous
Continuous Power Dissipation (TA= +70°C)
10-Pin TDFN (derate 24.4mW/°C above +70°C).....1951.2mW
12-Bump UCSP (derate 6.1mW/°C above +70°C)........484mW
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
Bump Temperature (soldering)
Reflow..........................................................................+235°C
MAX9705
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
GENERALSupply Voltage RangeVDDInferred from PSRR test2.55.5V
Quiescent CurrentIDD5.47mA
Shutdown CurrentISHDN0.310µA
Turn-On TimetON30ms
Input ResistanceRINTA = +25°C1220kΩ
MAX9705A0.881.01.12
MAX9705B0.730.830.93
MAX9705C0.610.710.81Input Bias VoltageVBIASEither input
MAX9705D0.480.560.64
MAX9705A1.92.02.1
MAX9705B3.84.04.2
MAX9705C5.76.06.3Voltage GainAV
MAX9705D9.51010.5
V/V
Output Offset VoltageVOSTA = +25°C±10±69mV
Common-Mode Rejection RatioCMRRfIN = 1kHz, input referred56dB
VDD = 2.5V to 5.5V, TA = +25°C5075
fRIPPLE = 217Hz75Power-Supply Rejection Ratio
(Note 3)PSRR200mVP-P ripplefRIPPLE = 20kHz60
RL = 8Ω600
Output PowerPOUTTHD+N = 1%,
fIN = 1kHz
RL = 4Ω
MAX9705_ETB+T and
MAX9705_EUB+ only
950mW
RL = 8Ω,
POUT = 450mW0.02Total Harmonic Distortion
Plus NoiseTHD+NfIN = 1kHz, either
FFM or SSMRL = 4Ω,
POUT = 375mW0.025
Into shutdown-68
Click/Pop LevelKCP
Peak voltage,
A-weighted
(Notes 3, 4)Out of shutdown-60.5
Output Slew RateSR176V/µs
MAX9705
2.3W, Ultra-Low-EMI, Filterless,
Class D Audio Amplifier
ELECTRICAL CHARACTERISTICS (continued)(VDD
= PVDD= VSHDN= 3.3V, VGND= VPGND= 0, SYNC = GND (FFM), RL= ∞, RLconnected between OUT+ and OUT-,= TMINto TMAX, unless otherwise noted. Typical values are at TA= +25°C.) (Notes 1, 2)
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= 4Ω, L = 33µH.
For RL= 8Ω, L = 68µH. For RL= 16Ω, L = 136µH.
Note 3:Inputs AC-coupled to GND.
Note 4:Testing performed with 8Ωresistive load in series with 68µH inductive load connected across BTL output. Mode transitions
are controlled by SHDNpin. KCPlevel is calculated as 20 x log[(peak voltage under normal operation at rated power
level)/(peak voltage during mode transition, no input signal)]. Units are expressed in dB.
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSRise/Fall TimetRISE, tFALL10% to 90%15ns
FFM91BW = 22Hz
to 22kHzSSM89
FFM93Signal-to-Noise RatioSNRVOUT = 2VRMS
A-weightedSSM91
SYNC = GND98011001220
Oscillator FrequencyfOSCSYNC = VDD (SSM mode)1220
±120
kHz
SYNC Frequency Lock Range8002000kHz
EfficiencyηPOUT = 800mW, fIN = 1kHz, RL = 8Ω89%
DIGITAL INPUTS (SHDN, SYNC)VIH2Input ThresholdsVIL0.8V
SHDN Input Leakage Current0.1±10µA
SYNC Input Current(Note 5)-1.25±10µA
ELECTRICAL CHARACTERISTICS (VDD
= PVDD= VSHDN= 5V, VGND= VPGND= 0, SYNC = GND (FFM), RL= ∞, RLconnected between OUT+ and OUT-,= TMINto TMAX, unless otherwise noted. Typical values are at TA= +25°C.) (Notes 1, 2)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSQuiescent CurrentIDD7mA
Shutdown CurrentISHDN0.55µA
f = 217Hz75Power-Supply Rejection RatioPSRR200mVP-P ripplef = 20kHz60dB
RL = 16Ω750
RL = 8Ω1400
Output PowerPOUTTHD+N = 1%,
f = 1kHzRL = 4Ω
MAX9705_ETB+T and
MAX9705_EUB+ only
RL = 8Ω, POUT = 1.0W0.02Total Harmonic Distortion
Plus NoiseTHD+Nf = 1kHz, either
FFM or SSMRL = 4Ω, POUT = 1.75W0.05%
FFM94BW = 22Hz to
22kHzSSM91
FFM97Signal-to-Noise RatioSNRVOUT =
3VRMS
A-weightedSSM93
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX9705toc04
OUTPUT POWER (W)
THD+N (%)
VDD = 3.3V
RL = 4Ω
fIN = 1kHz
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX9705toc05
OUTPUT POWER (W)
THD+N (%)
fIN = 1kHzVDD = 5.0V
RL = 4Ω
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX9705toc06
OUTPUT POWER (W)
THD+N (%)
VDD = 3.3V
RL = 8Ω
fIN = 1kHz
FFM
SSM
0.0110010k100k
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCYMAX9705toc07
THD+N (%)
VDD = 3.3V
RL = 8Ω
POUT = 100mW
POUT = 450mW
0.0110010k100k
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCYMAX9705toc08
THD+N (%)
VDD = 5.0V
RL = 8Ω
POUT = 250mW
POUT = 1W
0.0110010k100k
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCYMAX9705toc09
THD+N (%)
VDD = 2.5V
RL = 4Ω
POUT = 50mW
POUT = 300mW
MAX9705
2.3W, Ultra-Low-EMI, Filterless,
Class D Audio Amplifier
Typical Operating Characteristics(VDD= 3.3V, SYNC = VDD(SSM), differential input, TA= +25°C, unless otherwise noted. Typical Operating Characteristicsfor 4Ω
load condition apply to the MAX9705_ETB+T only.)
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX9705toc01
OUTPUT POWER (W)
THD+N (%)
fIN = 1kHz
VDD = 3.3V
RL = 8Ω
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX9705toc02
OUTPUT POWER (W)
THD+N (%)
fIN = 1kHzVDD = 5.0V
RL = 8Ω
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX9705toc03
OUTPUT POWER (W)
THD+N (%)
fIN = 1kHz
VDD = 2.5V
RL = 4Ω
MAX9705
Typical Operating Characteristics (continued)(VDD= 3.3V, SYNC = VDD(SSM), differential input, TA= +25°C, unless otherwise noted. Typical Operating Characteristicsfor 4Ω
load condition apply to the MAX9705_ETB+T only.)
0.0110010k100k
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCYMAX9705toc10
FREQUENCY (Hz)
THD+N (%)
VDD = 3.3V
RL = 4Ω
POUT = 100mW
POUT = 800mW
0.0110010k100k
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCYMAX9705toc11
FREQUENCY (Hz)
THD+N (%)
VDD = 5.0V
RL = 4Ω
POUT = 250mW
POUT = 1.75W
0.0110010k100k
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCYMAX9705toc12
FREQUENCY (Hz)
THD+N (%)
VDD = 3.3V
RL = 8Ω
POUT = 450mW
FFM
SSM
2.3W, Ultra-Low-EMI, Filterless,
Class D Audio AmplifierTOTAL HARMONIC DISTORTION PLUS
NOISE vs. COMMON-MODE VOLTAGE
MAX9705toc13
COMMON-MODE VOLTAGE (V)
THD+N (%)
VDD = 3.3V to 5V
fIN = 1kHz
POUT = 500mW
GAIN = 6dB
RL = 8Ω
EFFICIENCY
vs. OUTPUT POWER
MAX9705toc14
OUTPUT POWER (W)
EFFICIENCY (%)
VDD = 3.3V
fIN = 1kHz
RL = 8Ω
RL = 4Ω
EFFICIENCY
vs. OUTPUT POWER
MAX9705toc15
OUTPUT POWER (W)
EFFICIENCY (%)
VDD = 5.0V
fIN = 1kHz
RL = 8Ω
RL = 4Ω
EFFICIENCY
vs. SUPPLY VOLTAGE
MAX9705toc16
EFFICIENCY (%)
fIN = 1kHz
THD+N = 1%
RL = 8Ω
RL = 4Ω
EFFICIENCY
vs. SYNC FREQUENCY
MAX9705toc17
SYNC FREQUENCY (kHz)
EFFICIENCY (%)
VDD = 3.3V
fIN = 1kHz
THD+N = 1%
RL = 8Ω
RL = 4Ω
EFFICIENCY
vs. SYNC FREQUENCY
MAX9705toc18
EFFICIENCY (%)
VDD = 5.0V
fIN = 1kHz
THD+N = 1%
RL = 8Ω
RL = 4Ω
SPREAD-SPECTRUM-MODE OUTPUT
SPECTRUM vs. FREQUENCY
MAX9705 toc25
AMPLITUDE (dBV)
RL = 8Ω
VDD = 5.0V
fIN = 1kHz
A-WEIGHTED
MAX9705
2.3W, Ultra-Low-EMI, Filterless,
Class D Audio AmplifierOUTPUT POWER
vs. SUPPLY VOLTAGE
MAX9705toc19
SUPPLY VOLTAGE (V)
OUTPUT POWER (W)
fIN = 1kHz
RL = 8Ω
THD+N = 1%
THD+N = 10%
OUTPUT POWER
vs. SUPPLY VOLTAGE
MAX9705toc20
SUPPLY VOLTAGE (V)
OUTPUT POWER (W)
fIN = 1kHz
RL = 4Ω
THD+N = 1%
THD+N = 10%
OUTPUT POWER
vs. LOAD RESISTANCE
MAX9705 toc21
LOAD RESISTANCE (Ω)
OUTPUT POWER (W)
fIN = 1kHz
ZLOAD = 33μH IN
SERIES WITH RL
THD+N = 1%
3.3V
5.0V
-10010010k100k
POWER-SUPPLY REJECTION
RATIO vs. FREQUENCYMAX9705 toc22
FREQUENCY (Hz)
PSRR (dB)
VDD = 3.3V
VIN = 200mVP-P
RL = 8Ω
FIXED-FREQUENCY-MODE OUTPUT
SPECTRUM vs. FREQUENCY
MAX9705 toc23
FREQUENCY (kHz)
AMPLITUDE (dBV)
RL = 8Ω
VDD = 5.0V
fIN = 1kHz
BW = 22Hz to 22kHz
SPREAD-SPECTRUM-MODE OUTPUT
SPECTRUM vs. FREQUENCY
MAX9705 toc24
FREQUENCY (kHz)
AMPLITUDE (dBV)
RL = 8Ω
VDD = 5.0V
fIN = 1kHz
BW = 22Hz to 22kHz
Typical Operating Characteristics (continued)(VDD= 3.3V, SYNC = VDD(SSM), differential input, TA= +25°C, unless otherwise noted. Typical Operating Characteristicsfor 4Ω
load condition apply to the MAX9705_ETB+T only.)
MAX9705WIDEBAND OUTPUT SPECTRUM
FIXED-FREQUENCY MODE
MAX9705 toc26
FREQUENCY (MHz)
AMPLITUDE (dBV)
RL = 8Ω
VDD = 5.0V
INPUTS AC GROUNDED
WIDEBAND OUTPUT SPECTRUM
SPREAD-SPECTRUM MODE
MAX9705 toc27
FREQUENCY (MHz)
AMPLITUDE (dBV)
RL = 8Ω
VDD = 5.0V
INPUTS AC GROUNDED
2.3W, Ultra-Low-EMI, Filterless,
Class D Audio AmplifierSUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX9705 toc28
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (mA)
SYNC = VDD (SSM)
SYNC = GND (FFM)
NO LOAD
INPUTS AC GROUNDED
SUPPLY CURRENT
vs. TEMPERATURE
MAX9705 toc29
TEMPERATURE (°C)
SUPPLY CURRENT (mA)
SYNC = VDD (SSM)
SYNC = GND (FFM))
VDD = 3.3V
NO LOAD
INPUTS AC GROUNDED
SHUTDOWN CURRENT
vs. SUPPLY VOLTAGE
MAX9705 toc30
SUPPLY VOLTAGE (V)
SHUTDOWN CURRENT (
TA = +25°C
TA = +85°C
TA = -40°C
NO LOAD
INPUTS AC GROUNDED
SHDN = GND
TURN-ON/TURN-OFF RESPONSEMAX9705 toc31
MAX9705
OUTPUT
SHDN
250mV/div
10ms/divf = 1kHz
Typical Operating Characteristics (continued)(VDD= 3.3V, SYNC = VDD(SSM), differential input, TA= +25°C, unless otherwise noted. Typical Operating Characteristicsfor 4Ω
load condition apply to the MAX9705_ETB+T only.)
Functional DiagramMAX9705
(B1)
(B2)
(C1)
(B3)
( ) UCSP BUMP.
FIGURE SHOWS MAX9705 CONFIGURED FOR SPREAD-SPECTRUM OPERATION.
1μF
PGND
OUT+
OUT-
PVDD
PGND
PGND
PVDD
(C2)
GND
IN+
VDD
2.5V TO 5.5V
(A1)
SHDN
IN-
UVLO/POWER
MANAGEMENT
CLASS D
MODULATOR
PVDDSYNC
(B4)
(A3)
(A4)
(C4)
CLICK-AND-POP
SUPPRESSIONOSCILLATOR
1μF
1μF
LOW-EMI
DRIVER
LOW-EMI
DRIVER
MAX9705
2.3W, Ultra-Low-EMI, Filterless,
Class D Audio Amplifier
MAX9705
2.3W, Ultra-Low-EMI, Filterless,
Class D Audio Amplifier
Detailed DescriptionThe MAX9705 ultra-low-EMI, filterless, Class D audio
power amplifier features several improvements to switch-
mode amplifier technology. The MAX9705 features output
driver active emissions limiting circuitry to reduce EMI.
Zero dead time technology maintains state-of-the-art effi-
ciency and THD+N performance by allowing the output
FETs to switch simultaneously without cross-conduction.
A unique filterless modulation scheme, synchronizable
switching frequency, and spread-spectrum mode create
a compact, flexible, low-noise, efficient audio power
amplifier while occupying minimal board space. The dif-
ferential input architecture reduces common-mode noise
pickup with or without the use of input-coupling capaci-
tors. The MAX9705 can also be configured as a single-
ended input amplifier without performance degradation.
Thermal-overload and short-circuit protection prevent the
MAX9705 from being damaged during a fault condition.
The amplifier is disabled if the die temperature reaches
+125°C. The die must cool by 10°C before normal opera-
tion can continue. The output of the MAX9705 shuts down
if the output current reaches approximately 2A. Each out-
put FET has its own short-circuit protection. This protec-
tion scheme allows the amplifier to survive shorts to either
supply rail. After a thermal overload or short circuit, the
device remains disabled for a minimum of 50µs before
attempting to return to normal operation. The amplifier will
shut down immediately and wait another 50µs before turn-
ing on if the fault condition is still present. This operation
will cause the output to pulse during a persistent fault.
Comparators monitor the MAX9705 inputs and com-
pare the complementary input voltages to the sawtooth
waveform. The comparators trip when the input magni-
tude of the sawtooth exceeds their corresponding input
voltage. Both comparators reset at a fixed time after the
rising edge of the second comparator trip point, gener-
ating a minimum-width pulse tON(MIN)at the output of
the second comparator (Figure 1). As the input voltage
increases or decreases, the duration of the pulse at one
output increases (the first comparator to trip), while the
other output pulse duration remains at tON(MIN). This
causes the net voltage across the speaker (VOUT+-
VOUT-) to change.
Operating Modes
Fixed-Frequency Modulation (FFM) ModeThe FFM mode is selected by setting SYNC = GND for a
1.1MHz switching frequency. In FFM mode, the frequen-
cy spectrum of the Class D output consists of the funda-
mental switching frequency and its associated
harmonics (see the Wideband Output Spectrum Fixed-
Frequency Mode graph in the Typical Operating
Characteristics).
Pin Description
PINBUMP
TDFNUCSPNAMEFUNCTION1A1VDDAnalog Power SupplyB1IN+Noninverting Audio InputC1IN-Inverting Audio InputC2GNDAnalog Ground
5B2SHDNActive-Low Shutdown Input. Connect to VDD for normal operation.A3SYNC
Frequency Select and External Clock Input.
SYNC = GND: Fixed-frequency mode with fS = 1100kHz.
SYNC = VDD: Spread-spectrum mode with fS = 1220kHz ±120kHz.
SYNC = Clocked: Fixed-frequency mode with fS = external clock frequency.B3PGNDPower GroundA4OUT+Amplifier-Output Positive PhaseC4OUT-Amplifier-Output Negative PhaseB4PVDDH-Bridge Power SupplyEP
Exposed Pad. Internally connected to ground. Connect to a large ground plane to
maximize thermal performance. Not intended as an electrical connection point
(TDFN only).
