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19-3681; Rev 0; 12/05
KIT ATION EVALU LE B AVAILA
3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover
General Description
The MAX9706/MAX9707 combine three high-efficiency Class D amplifiers with an active crossover to provide stereo highpass outputs, and a mono lowpass output. All three channels deliver up to 2.3W at 1% THD+N per channel into 4 when operating from a 5V supply. An internal active filter processes the stereo inputs (left and right) into stereo highpass and mono lowpass outputs. The crossover frequency is pin-selectable to four different frequencies to accommodate a variety of speaker configurations. The internal Class D amplifiers feature low-EMI, spread-spectrum outputs. No output filters are required. The MAX9706 features Maxim's patented DirectDriveTM headphone amplifier, providing ground-referenced headphone outputs without the need for bulky DC-coupling capacitors. The headphone outputs are capable of delivering 95mW per channel into 16 from a 3.3V supply, and are protected against ESD up to 8kV. The MAX9706/MAX9707 feature pin-programmable gain, synchronization inputs and outputs, and a shutdown mode that reduces supply current to less than 1A. All amplifiers feature click-and-pop suppression circuitry. Both devices are fully specified over the -40C to +85C extended temperature range and are available in the thermally enhanced 36-pin (6mm x 6mm x 0.8mm) thin QFN package.
Features
Triple Class D Amplifiers Deliver 3 x 2.3W into 4 Internal Active Crossover Filter with Adjustable Crossover Frequency Low-EMI, Spread-Spectrum Modulation Low 0.02% THD+N High PSRR (71dB) DirectDrive Headphone Amplifier (MAX9706) Enhanced Click-and-Pop Suppression Input and Output Modulator Synchronization Low-Power Shutdown Mode Up To 90% Efficiency Space-Saving (6mm x 6mm x 0.8mm) 36-Pin Thin QFN Package
MAX9706/MAX9707
Ordering Information
PART MAX9706ETX+ MAX9707ETX+ HP AMP Yes No PIN-PACKAGE 36 Thin QFN 36 Thin QFN PKG CODE T3666N-1 T3666N-1
+Denotes lead-free package. Note: These devices operate over the -40C to +85C temperature range. Functional Diagrams and Pin Configurations appear at end of data sheet.
Applications
Notebook Audio Solutions 2.1 Speaker Solutions Desktop PCs Multimedia Monitors Portable DVD Players Table-Top LCD TVs
Block Diagram
MAX9706 MAX9707
FULL-RANGE TRANSDUCERS AUDIO IN
AUDIO IN
FULL-RANGE TRANSDUCERS
LOW-FREQUENCY TRANSDUCER FREQUENCY SELECT HEADPHONE
LOW-FREQUENCY TRANSDUCER FREQUENCY SELECT SHDN
SHDN
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover MAX9706/MAX9707
ABSOLUTE MAXIMUM RATINGS
VDD, PVDD, HPVDD, CPVDD to GND ........................-0.3V to +6V GND to PGND, CPGND.........................................-0.3V to +0.3V CPVSS, VSS to GND..................................................-6V to +0.3V C1N to GND ...........................................(CPVSS - 0.3V) to +0.3V C1P to GND ...........................................-0.3V to (CPVDD + 0.3V) HPL, HPR.....................................................................-3V to +3V All Other Pins to GND.................................-0.3V to (VDD + 0.3V) OUT_+, OUT_ -, Short Circuit to GND or PVDD ...........Continuous OUT_+ Short Circuit to OUT_-....................................Continuous HPR, HPL Short Circuit to GND..................................Continuous MONO_OUT Short Circuit to GND or VDD ....................Continuous Continuous Current (PVDD, OUT_+, OUT_-, PGND).............1.7A Continuous Current (MONO_OUT, CPVDD, C1N, C1P, CPGND, CPVSS, VSS, HPVDD, HPR, HPL) ......................0.85A Continuous Current (all other pins) .....................................20mA Continuous Power Dissipation (TA = +70C) Single-Layer Board 36-Pin TQFN (derate 26.3mW/C above +70C) .......2105mW Multilayer Board 36-Pin TQFN (derate 35.7mW/C above +70C) .......2857mW Operating Temperature Range ...........................-40C to +85C Storage Temperature Range .............................-65C to +150C Junction Temperature ......................................................+150C Lead Temperature (soldering, 10s) .................................+300C
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
(VDD = PVDD = HPVDD = 5V, GND = PGND = CPGND = 0V, SHDN = VDD, GAIN1 = GAIN2 = GND (SPKR = +9dB, HP = 0dB), HPS = GND, FS0 = FS1 = GND (800Hz), MGAIN = float (-6dB), SYNC_IN = VDD (SSM), speaker load RL connected between OUT_+ and OUT_-, unless otherwise noted, RL = . Headphone load RLH connected between HPR/HPL to GND, RLH = . CBIAS = 1F to GND, C1 = 1F, C2 = 1F. TA = TMIN to TMAX, unless otherwise noted. Typical values at TA = +25C.) (Note 1)
PARAMETER Speaker Amplifier Supply Voltage Range Headphone Amplifier Supply Voltage Range Quiescent Supply Current Shutdown Supply Current Input Resistance Turn-On Time, Shutdown to Full Operation SYMBOL CONDITIONS MIN 4.5 3.0 25 7 0.5 15 Speaker mode Headphone mode (MAX9706) RL = 8, THD+N = 1% RL = 4, THD+N = 1% POUT = 1W, bandwidth = 22Hz to 22kHz (Note 2) RL = 8, POUT = 1W (Note 2) RL = 8 RL = 4 Bandwidth = 22Hz to 22kHz A-weighted VDD = PVDD = 4.5V to 5.5V, TA = +25C Power-Supply Rejection Ratio PSRR 100mVP-P ripple (Note 3) f = 2kHz, OUTL_, OUTR_ f = 100Hz, OUTM_ 50 25 87 87 1.4 2.3 0.06 % 0.07 87 92 71 51 65 dB TYP MAX 5.5 5.5 35 12 3 35 UNITS V V mA A k ms
VDD, PVDD Inferred from PSRR test HPVDD, CPVDD IDD ISHDN RIN Inferred from PSRR test (MAX9706) Speaker mode Headphone mode, HPS = VDD (MAX9706) SHDN = GND
SPEAKER AMPLIFIERS (OUTL_, OUTR_, OUTM_) Output Power (Note 2) Total Harmonic Distortion Plus Noise POUT W
THD+N
Signal-to-Noise Ratio
SNR
dB
2
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3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover
ELECTRICAL CHARACTERISTICS (continued)
(VDD = PVDD = HPVDD = 5V, GND = PGND = CPGND = 0V, SHDN = VDD, GAIN1 = GAIN2 = GND (SPKR = +9dB, HP = 0dB), HPS = GND, FS0 = FS1 = GND (800Hz), MGAIN = float (-6dB), SYNC_IN = VDD (SSM), speaker load RL connected between OUT_+ and OUT_-, unless otherwise noted, RL = . Headphone load RLH connected between HPR/HPL to GND, RLH = . CBIAS = 1F to GND, C1 = 1F, C2 = 1F. TA = TMIN to TMAX, unless otherwise noted. Typical values at TA = +25C.) (Note 1)
PARAMETER SYMBOL GAIN2 = 0 Speaker Path Gain (Note 4) GAIN2 = 0 GAIN2 = 1 GAIN2 = 1 Channel-to-Channel Gain Tracking MGAIN = GND MONO Gain Offset (Note 5) MGAIN = float MGAIN = VDD Crosstalk Maximum Capacitive Load Efficiency CL Right to left, left to right, fIN = 10kHz, POUT = 1W No sustained oscillations RL = 8, POUT = 3 x 1W, f = 800Hz RL = 4, POUT = 3 x 1W, f = 800Hz FFM, SYNC_IN = GND Class D Center Frequency Class D Spreading Bandwidth SYNC_IN Frequency Lock Range Output Offset Voltage Click-and-Pop Level CROSSOVER FILTERS Cutoff Frequency Accuracy (Note 7) FS0 = 0 Crossover Frequency fXO FS0 = 0 FS0 = 1 FS0 = 1 Left-to-Right Cutoff Frequency Tracking FS1 = 0 FS1 = 1 FS1 = 0 FS1 = 1 800 1066.7 1600 2133.3 0.5 % Hz 15 % VOS KCP OUT_+ to OUT_Peak voltage, A-weighted, 32 samples per second (Note 6) Into shutdown Out of shutdown fOSC FFM, SYNC_IN = float SSM, SYNC_IN = VDD SSM mode, SYNC_IN = VDD 1000 14 47 dBV 50 955 1140 CONDITIONS GAIN1 = 0 GAIN1 = 1 GAIN1 = 0 GAIN1 = 1 MIN TYP 9 10.5 12 13.5 0.3 -4.5 -6 -7.5 70 200 90 88 1100 1340 1150 50 1500 kHz kHz mV 1270 1540 kHz dB pF % dB % dB MAX UNITS
MAX9706/MAX9707
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3
3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover MAX9706/MAX9707
ELECTRICAL CHARACTERISTICS (continued)
(VDD = PVDD = HPVDD = 5V, GND = PGND = CPGND = 0V, SHDN = VDD, GAIN1 = GAIN2 = GND (SPKR = +9dB, HP = 0dB), HPS = GND, FS0 = FS1 = GND (800Hz), MGAIN = float (-6dB), SYNC_IN = VDD (SSM), speaker load RL connected between OUT_+ and OUT_-, unless otherwise noted, RL = . Headphone load RLH connected between HPR/HPL to GND, RLH = . CBIAS = 1F to GND, C1 = 1F, C2 = 1F. TA = TMIN to TMAX, unless otherwise noted. Typical values at TA = +25C.) (Note 1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
HEADPHONE AMPLIFIERS (MAX9706) (HPS = VDD) Output Power POUT HPVDD = 3.3V to 5V, TA = +25C, THD+N = 1% (Notes 2, 7) VOUT = 1VRMS, f = 1kHz, bandwidth = 22Hz to 22kHz VOUT = 1VRMS HPVDD = 3V to 5.5V Power-Supply Rejection Ratio PSRR f = 1kHz, 100mVP-P ripple (Note 3) f = 20kHz, 100mVP-P ripple (Note 3) Headphone Path Gain (Note 8) Output Offset Voltage Crosstalk Slew Rate Maximum Capacitive Load HPS Pullup Impedance Debounce Time Output Impedance in Shutdown Charge-Pump Switching Frequency Click-and-Pop Level fCP Peak voltage, A-weighted, 32 samples per second (Note 6) Into shutdown Out of shutdown HPS = GND or SHDN = GND CL No sustained oscillations VOSHP GAIN2 = 0 GAIN2 = 1 HP_ to GND, TA = +25C HPL to HPR, HPR to HPL, fIN = 1kHz, POUT = 32mW, RL = 32 RL = 32 RL = 16 RL = 32 RL = 16 Bandwidth = 22Hz to 22kHz A-weighted 70 35 50 mW 95 0.02 % 0.04 96 100 90 80 65 0 3 0.7 -60 0.5 300 600 65 1.4 fOSC / 2 52 52 dBV 3 dB mV dB V/s pF k ms k kHz dB
Total Harmonic Distortion Plus Noise
THD+N
Signal-to-Noise Ratio
SNR
dB
KCP
LINE-LEVEL MONO OUTPUT (MONO_OUT) MONO_OUT Signal-Path Gain Output Impedance Maximum Output Level Total Harmonic Distortion Plus Noise Maximum Capacitive Load THD+N CL RL = 10k VOUT = 1VRMS, fIN = 100Hz, RL = 10k, bandwidth = 22Hz to 22kHz No sustained oscillations 0 0.1 1 0.01 200 dB VRMS % pF
4
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3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover
ELECTRICAL CHARACTERISTICS (continued)
(VDD = PVDD = HPVDD = 5V, GND = PGND = CPGND = 0V, SHDN = VDD, GAIN1 = GAIN2 = GND (SPKR = +9dB, HP = 0dB), HPS = GND, FS0 = FS1 = GND (800Hz), MGAIN = float (-6dB), SYNC_IN = VDD (SSM), speaker load RL connected between OUT_+ and OUT_-, unless otherwise noted, RL = . Headphone load RLH connected between HPR/HPL to GND, RLH = . CBIAS = 1F to GND, C1 = 1F, C2 = 1F. TA = TMIN to TMAX, unless otherwise noted. Typical values at TA = +25C.) (Note 1)
PARAMETER Input-Voltage High Input-Voltage Low Input Leakage Current Input Current Pullup Impedance DIGITAL OUTPUT (SYNC_OUT) Output-Voltage High Output-Voltage Low VOH VOL IOH = 1mA IOL = 1mA VDD x 0.9 VDD x 0.1 V V SYMBOL VINH VINL GAIN1, GAIN2, FS0, FS1, SHDN SYNC_IN, MGAIN SYNC_IN, MGAIN 200 CONDITIONS MIN 2 0.8 1 50 TYP MAX UNITS V V A A k DIGITAL INPUTS (GAIN1, GAIN2, FS0, FS1, SHDN, SYNC_IN, MGAIN)
MAX9706/MAX9707
Note 1: Note 2: Note 3: Note 4:
All devices are 100% tested at TA = +25C. Limits over temperature are guaranteed by design. Measured at 2kHz for OUTL_, OUTR_, HPL, and HPR; measured at 100Hz for OUTM_. PSRR is measured with the inputs AC-grounded. Left/right signal-path gain is defined as:
(VOUT _ + ) - (VOUT _ - )
VIN _
MONO signal-path gain is defined as:
(VOUTM + ) - (VOUTM - ) (VINL ) + (VINR )
Note 5: MONO gain offset is measured with respect to speaker-path gain. Note 6: Speaker mode testing performed with an 8 resistive load in series with a 68H inductive load connected across BTL output. Headphone mode testing performed with a 32 resistive load connected between HP_ and GND. Mode transitions are controlled by SHDN. Note 7: Headphone-path gain is defined as:
VHP VIN _
Note 8: Guaranteed by design only.
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5
3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover MAX9706/MAX9707
Typical Operating Characteristics--Speaker Mode
(VDD = PVDD = HPVDD = 5V, GND = PGND = CPGND = 0V, SHDN = VDD, GAIN1 = GAIN2 = GND (+9dB), FS0 = FS1 = GND (800Hz), MGAIN = float (-6dB), SYNC_IN = VDD (SSM), speaker load RL connected between OUT+ and OUT-, unless otherwise noted, RL = . Headphone load RLH connected between HPR/HPL to GND. CBIAS = 1F to GND, 1F capacitor between C1P and C1N, CVSS = 1F. TA = TMIN to TMAX, unless otherwise noted. Typical values at TA = +25C.)
TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY
MAX9706 toc01
TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY
MAX9706 toc02
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
VDD = 5V RL = 4
MAX9706 toc03
10
VDD = 5V RL = 4 OUTPUT POWER = 1.5W OUTL AND OUTR
10
VDD = 5V RL = 8 OUTPUT POWER = 900mW OUTL AND OUTR
100
1 THD+N (%) THD+N (%)
1 THD+N (%)
10
1 fIN = 2kHz fIN = 200Hz 0.1
0.1
0.1
0.01 OUTM 0.001 10 100 1k FREQUENCY (Hz) 10k 100k
0.01 OUTM 0.001 10 100 1k FREQUENCY (Hz) 10k 100k
0.01 fIN = 10kHz 0.001 0 0.5 1.0 1.5 2.0 2.5 3.0 OUTPUT POWER (W)
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
MAX9706 toc04
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
MAX9706 toc05
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
VDD = 5V RL = 8 fIN = 1kHz
MAX9706 toc06
100
100
VDD = 5V RL = 8
10
10
VDD = 5V RL = 8 fIN = 1kHz
100
10
THD+N (%)
THD+N (%)
1 fIN = 2kHz 0.1
1 SYNC_IN = FLOAT 0.1
THD+N (%)
1
SYNC_IN = 2MHz
0.1
0.01
fIN = 200Hz
fIN = 10kHz
0.01
SYNC_IN = VDD
SYNC_IN = GND
0.01 SYNC_IN = 0.8MHz
SYNC_IN = 1.4MHz
0.001 0 0.3 0.6 0.9 1.2 1.5 1.8 OUTPUT POWER (W)
0.001 0 0.5 1.0 OUTPUT POWER (W) 1.5 2.0
0.001 0 0.5 1.0 OUTPUT POWER (W) 1.5 2.0
6
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3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover
Typical Operating Characteristics--Speaker Mode (continued)
(VDD = PVDD = HPVDD = 5V, GND = PGND = CPGND = 0V, SHDN = VDD, GAIN1 = GAIN2 = GND (+9dB), FS0 = FS1 = GND (800Hz), MGAIN = float (-6dB), SYNC_IN = VDD (SSM), speaker load RL connected between OUT+ and OUT-, unless otherwise noted, RL = . Headphone load RLH connected between HPR/HPL to GND. CBIAS = 1F to GND, 1F capacitor between C1P and C1N, CVSS = 1F. TA = TMIN to TMAX, unless otherwise noted. Typical values at TA = +25C.)
OUTPUT POWER vs. LOAD RESISTANCE
MAX9706 toc07
MAX9706/MAX9707
OUTPUT POWER vs. SUPPLY VOLTAGE
MAX9706 toc08
OUTPUT POWER vs. SUPPLY VOLTAGE
f = 1kHz RL = 8 THD+N = 10%
MAX9706 toc09
4.0 3.5 OUTPUT POWER (W) 3.0 2.5 2.0 1.5 1.0 0.5 0 1 10 LOAD RESISTANCE () THD+N = 1% THD+N = 10% VDD = 5V f = 1kHz
4.0 3.5 OUTPUT POWER (W) 3.0 2.5 2.0 1.5 1.0 0.5 0 THD+N = 1% f = 1kHz RL = 4 THD+N = 10%
3.0 2.5 OUTPUT POWER (W) 2.0 1.5 1.0 0.5 0 THD+N = 1%
100
4.5
4.7
4.9
5.1
5.3
5.5
4.5
4.7
4.9
5.1
5.3
5.5
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
EFFICIENCY vs. OUTPUT POWER
MAX9706 toc10
POWER-SUPPLY REJECTION RATIO vs. FREQUENCY
MAX9706 toc11
OUTPUT FREQUENCY SPECTRUM
SSM MODE VOUT = -60dB f = 1kHz RL = 8 UNWEIGHTED
MAX9706 toc12
100 90 80 EFFICIENCY (%) 70 60 50 40 30 20 10 0 0 1 POUT = POUTL + POUTR + POUTM fIN = 800Hz 2 3 4 5 RL = 4 RL = 8
0 -10 -20 -30 -40 -50 -60 -70 -80 -90 -100 -110 -120 10 PSRR (dB)
VRIPPLE = 100mVP-P RL = 8 OUTM
0 -20 OUTPUT MAGNITUDE (dBV) -40 -60 -80 -100 -120 -140
OUTR
OUTL
100
1k FREQUENCY (Hz)
10k
100k
0
5
10 FREQUENCY (kHz)
15
20
OUTPUT POWER (W)
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7
3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover MAX9706/MAX9707
Typical Operating Characteristics--Speaker Mode (continued)
(VDD = PVDD = HPVDD = 5V, GND = PGND = CPGND = 0V, SHDN = VDD, GAIN1 = GAIN2 = GND (+9dB), FS0 = FS1 = GND (800Hz), MGAIN = float (-6dB), SYNC_IN = VDD (SSM), speaker load RL connected between OUT+ and OUT-, unless otherwise noted, RL = . Headphone load RLH connected between HPR/HPL to GND. CBIAS = 1F to GND, 1F capacitor between C1P and C1N, CVSS = 1F. TA = TMIN to TMAX, unless otherwise noted. Typical values at TA = +25C.)
WIDEBAND OUTPUT SPECTRUM (FFM MODE)
MAX9706 toc14 MAX9706 toc13
OUTPUT FREQUENCY SPECTRUM
0 -20 OUTPUT MAGNITUDE (dBV) -40 -60 -80 -100 -120 -140 0 5 10 FREQUENCY (kHz) 15 20 SSM MODE VOUT = -60dB f = 1kHz RL = 8 A-WEIGHTED 20 10 OUTPUT AMPLITUDE (dBV) 0 -10 -20 -30 -40 -50 -60 -70 -80 0
WIDEBAND OUTPUT SPECTRUM (SSM MODE)
10 OUTPUT AMPLITUDE (dBV) 0 -10 -20 -30 -40 -50 -60 -70 -80 RBW = 10kHz INPUT AC-GROUNDED
MAX9706 toc15 MAX9706 toc18
20
RBW = 10kHz INPUT AC-GROUNDED
1
10 FREQUENCY (MHz)
100
1000
0
1
10 FREQUENCY (MHz)
100
1000
TURN-ON/-OFF RESPONSE
MAX9706 toc16
AMPLITUDE vs. FREQUENCY
fXO = 800Hz
MAX9706 toc17
AMPLITUDE vs. FREQUENCY
20 10 AMPLITUDE (dBV) 0 -10 -20 -30 -40 -50 fXO = 2.1kHz
20 10 AMPLITUDE (dBV) 2V/div 0 -10 -20 -30 -40 -50
200mA/div
20ms/div
10
100
1k FREQUENCY (Hz)
10k
100k
10
100
1k FREQUENCY (Hz)
10k
100k
8
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3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover
Typical Operating Characteristics--Headphone Mode
(VDD = PVDD = HPVDD = 5V, GND = PGND = CPGND = 0V, SHDN = VDD, GAIN1 = GAIN2 = GND (+9dB), FS0 = FS1 = GND (800Hz), MGAIN = float (-6dB), SYNC_IN = VDD (SSM), speaker load RL connected between OUT+ and OUT-, unless otherwise noted, RL = . Headphone load RLH connected between HPR/HPL to GND. CBIAS = 1F to GND, 1F capacitor between C1P and C1N, CVSS = 1F. TA = TMIN to TMAX, unless otherwise noted. Typical values at TA = +25C.)
TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY
MAX9706 toc19
MAX9706/MAX9707
TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY
MAX9706 toc20
TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY
HPVDD = 5V RL = 16
MAX9706 toc21
10
HPVDD = 3.3V RL = 16
10
HPVDD = 3.3V RL = 32
10
1 THD+N (%) THD+N (%) OUTPUT POWER = 25mW 0.1
1 THD+N (%)
1
0.1
OUTPUT POWER = 10mW
0.1
OUTPUT POWER = 20mW
0.01
OUTPUT POWER = 75mW
0.01 OUTPUT POWER = 35mW
0.01
OUTPUT POWER = 80mW
0.001 10 100 1k FREQUENCY (Hz) 10k 100k
0.001 10 100 1k FREQUENCY (Hz) 10k 100k
0.001 10 100 1k FREQUENCY (Hz) 10k 100k
TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY
MAX9706 toc22
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
MAX9706 toc23
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
HPVDD = 3.3V RL = 32
MAX9706 toc24
10
HPVDD = 5V RL = 32
100
HPVDD = 3.3V RL = 16
100
1 THD+N (%) THD+N (%)
10
10
1 fIN = 1kHz 0.1 fIN = 200Hz
THD+N (%)
1 fIN = 1kHz
0.1
OUTPUT POWER = 10mW
0.1
fIN = 10kHz
0.01 OUTPUT POWER = 35mW 0.001 10 100 1k FREQUENCY (Hz) 10k 100k
0.01 fIN = 10kHz
0.01 fIN = 200Hz
0.001 0 15 30 45 60 75 90 105 120 135 OUTPUT POWER (mW)
0.001 0 10 20 30 40 50 60 70 OUTPUT POWER (mW)
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9
3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover MAX9706/MAX9707
Typical Operating Characteristics--Headphone Mode (continued)
(VDD = PVDD = HPVDD = 5V, GND = PGND = CPGND = 0V, SHDN = VDD, GAIN1 = GAIN2 = GND (+9dB), FS0 = FS1 = GND (800Hz), MGAIN = float (-6dB), SYNC_IN = VDD (SSM), speaker load RL connected between OUT+ and OUT-, unless otherwise noted, RL = . Headphone load RLH connected between HPR/HPL to GND. CBIAS = 1F to GND, 1F capacitor between C1P and C1N, CVSS = 1F. TA = TMIN to TMAX, unless otherwise noted. Typical values at TA = +25C.)
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
MAX9706 toc25
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
MAX9706 toc26
OUTPUT POWER vs. LOAD RESISTANCE
HPVDD = 3.3V f = 1kHz
MAX9706 toc27 MAX9706 toc30
100
HPVDD = 5V RL = 16
100
140 120 OUTPUT POWER (mW) 100 80 60 40 20 THD+N = 1% THD+N = 10%
HPVDD = 5V RL = 32
10
10
THD+N (%)
1 fIN = 10kHz 0.1 fIN = 1kHz
THD+N (%)
1 fIN = 10kHz
0.1
fIN = 1kHz
0.01 fIN = 200Hz 0.001 0 20 40 60 80 100 120 OUTPUT POWER (mW)
0.01 fIN = 200Hz 0 10 20 30 40 50 60 70
0.001
0 10 100 LOAD RESISTANCE () 1000
OUTPUT POWER (mW)
OUTPUT POWER vs. LOAD RESISTANCE
MAX9706 toc28
OUTPUT POWER vs. HEADPHONE SUPPLY VOLTAGE
MAX9706 toc29
POWER-SUPPLY REJECTION RATIO vs. FREQUENCY
0 -20 -40 VRIPPLE ON VDD AND HPVDD = 100mVP-P INPUTS AC-GROUNDED
140 120 OUTPUT POWER (mW) 100 80 60 40 20 0 10 100 LOAD RESISTANCE () THD+N = 1% THD+N = 10% HPVDD = 5V f = 1kHz
130 THD+N = 1% 110 OUTPUT POWER (mW) RL = 16 90
PSRR (dB)
-60 -80
LEFT
70 RL = 32 50
-100 -120 3.0 3.5 4.0 4.5 5.0 5.5 10 100 1k FREQUENCY (Hz)
RIGHT
30 1000 HPVDD (V)
10k
100k
10
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3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover
Typical Operating Characteristics--Headphone Mode (continued)
(VDD = PVDD = HPVDD = 5V, GND = PGND = CPGND = 0V, SHDN = VDD, GAIN1 = GAIN2 = GND (+9dB), FS0 = FS1 = GND (800Hz), MGAIN = float (-6dB), SYNC_IN = VDD (SSM), speaker load RL connected between OUT+ and OUT-, unless otherwise noted, RL = . Headphone load RLH connected between HPR/HPL to GND. CBIAS = 1F to GND, 1F capacitor between C1P and C1N, CVSS = 1F. TA = TMIN to TMAX, unless otherwise noted. Typical values at TA = +25C.)
POWER-SUPPLY REJECTION RATIO vs. FREQUENCY
MAX9706 toc31
MAX9706/MAX9707
CROSSTALK vs. FREQUENCY
MAX9706 toc32
OUTPUT POWER vs. CHARGE-PUMP CAPACITANCE
90 OUTPUT POWER (mW) 80 70 60 50 40 C1 = C2 = 1F C1 = C2 = 0.47F f = 1kHz THD+N = 1%
MAX9706 toc33
0 -20 -40 PSRR (dB) -60
VRIPPLE = 100mVP-P INPUTS AC-GROUNDED
0 -10 -20 CROSSTALK (dB) -30 -40 -50 -60
RL = 32 POUT = 32mW
100
RIGHT -80 -100 LEFT -120 10 100 1k FREQUENCY (Hz) 10k 100k
LEFT TO RIGHT
-70 -80 10
RIGHT TO LEFT 100 1k FREQUENCY (Hz) 10k 100k
30 20 15 20
C1 = C2 = 0.22F
25
30
35
40
45
50
LOAD ()
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX9706 toc34
OUTPUT FREQUENCY SPECTRUM
VOUT = -60dBV f = 1kHz RL = 32
MAX9706 toc35
TURN-ON/-OFF RESPONSE
MAX9706 toc36
40
0 -20 OUTPUT MAGNITUDE (dBV) -40 -60 -80 -100 -120
SUPPLY VOLTAGE = IVDD + IHPVDD
SUPPLY CURRENT (mA)
30 HPS = GND HPVDD = 3.3V 20
2V/div
10
HPS = VDD VDD = 5V
1V/div
0 3.0 3.5 4.0 4.5 5.0 5.5 SUPPLY VOLTAGE (V)
-140 0 5 10 FREQUENCY (kHz) 15 20 100ms/div
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11
3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover MAX9706/MAX9707
Pin Description
PIN MAX9706 1 2 3 MAX9707 1 2 3 NAME BIAS GND VDD FUNCTION Internal Bias. Bypass BIAS to GND with a 1F capacitor. Ground. Star connect to PGND (see the Supply Bypassing, Layout, and Grounding section). Main Power Supply. Connect VDD to a low-noise 5V source. Bypass VDD to GND with a 1F capacitor.
4 5, 23, 31 6 7 8, 20, 34 9 10 11 12 13
4 5, 23, 31 6 7 8, 20, 34 -- -- -- -- --
Synchronization Clock Output. Connect SYNC_OUT to other Class D amplifiers to maintain SYNC_OUT synchronization. SYNC_OUT is a CMOS output proportional to VDD. Float SYNC_OUT, if not used. PGND OUTLOUTL+ PVDD CPVDD C1P CPGND C1N CPVSS Power Ground. PGND is the ground connection for the speaker amplifiers. Left-Speaker Negative Terminal Left-Speaker Positive Terminal Output Power Supply. PVDD is the power connection for the speaker amplifiers. Connect to VDD. Bypass each PVDD to its corresponding PGND with a 1F capacitor. Charge-Pump Positive Supply. Connect CPVDD to HPVDD. Bypass CPVDD to CPGND with a 1F capacitor. Charge-Pump Flying Capacitor Positive Terminal. Connect a 1F capacitor from C1P to C1N. Charge-Pump Ground. Connect to PGND. Charge-Pump Flying Capacitor Negative Terminal. Connect a 1F capacitor from C1N to C1P. Negative Supply Charge-Pump Output. Bypass CPVSS to PGND with a 1F capacitor. Connect CPVSS to VSS. Frequency Select or External Clock Input. Connect SYNC_IN to GND, VDD, leave floating, or drive with an externally generated clock to control the switching frequency of the Class D amplifiers. See Table 1. Headphone Sense. HPS is a digital input with a pullup resistor to detect the connection of a headphone. When HPS is high, the headphone amplifier is enabled and the Class D speaker amplifiers are disabled. See the Headphone Sense Input (HPS) section. Headphone Amplifier Negative Supply. Connect VSS to CPVSS. Right Headphone Output Left Headphone Output Positive Supply for Headphone Amplifiers. Connect HPVDD to VDD. Bypass HPVDD to PGND with a 0.1F capacitor. Right-Speaker Positive Terminal Right-Speaker Negative Terminal Shutdown Input. Drive SHDN low to put the MAX9706/MAX9707 in low-power shutdown mode. Drive SHDN high or connect to VDD to enable normal operation. Crossover Frequency Select. Connect FS0 and FS1 to GND or VDD to set the crossover frequency. See Table 4.
14
14
SYNC_IN
15 16 17 18 19 21 22 24 25 26
-- -- -- -- -- 21 22 24 25 26
HPS VSS HPR HPL HPVDD OUTR+ OUTRSHDN FS0 FS1
12
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3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover
Pin Description (continued)
PIN MAX9706 27 28 29 30 32 33 35 36 -- -- EP MAX9707 27 28 29 30 32 33 35 36 9-13, 16-19 15 EP NAME INR MGAIN GAIN2 GAIN1 OUTMOUTM+ MONO_OUT INL N.C. I.C. EP FUNCTION Right-Channel Audio Input. Connect the right-channel audio signal to INR with a series capacitor. INR has a 25k typical input impedance. Mono Gain Control. Connect MGAIN to GND, VDD, or leave floating to set the gain of the MONO channel with respect to the left and right channels. See Table 3. Amplifier Gain-Control Input. Connect GAIN1 and GAIN2 to GND or VDD to set the gain of the left and right channels. See Tables 2 and 4. Amplifier Gain-Control Input. Connect GAIN1 and GAIN2 to GND or VDD to set the gain of the left and right channels. See Tables 2 and 4. Mono-Speaker Negative Terminal Mono-Speaker Positive Terminal Mono Line-Level Output. MONO_OUT is the monaural output of the summed left and right lowfrequency signals. Left-Channel Audio Input. Connect the left-channel audio signal to INL with a series capacitor. INL has a 25k typical input impedance. No Connection. Not internally connected. Internally Connected. Connect to GND. Exposed Pad. The external pad lowers the package's thermal impedance by providing a direct heat conduction path from the die to the PC board. The exposed pad is not internally connected. Connect the exposed pad to GND.
MAX9706/MAX9707
Detailed Description
The MAX9706/MAX9707 combine three high-efficiency Class D amplifiers with an active crossover to provide stereo highpass outputs, and a mono lowpass output (Figure 1). All three channels deliver up to 2.3W per channel into 4 when operating from a 5V supply. An internal active filter processes the stereo inputs (left and right) into stereo highpass and mono lowpass outputs. The crossover frequency is pin-selectable to four different frequencies to accommodate a variety of speaker configurations. The internal Class D amplifiers feature low-EMI, spreadspectrum outputs. No output filters are required. The MAX9706 features Maxim's patented DirectDrive headphone amplifier, providing ground-referenced headphone outputs without the need for bulky coupling capacitors. The headphone outputs are capable of delivering 95mW per channel into 16 from a 3.3V supply, and are protected against ESD up to 8kV.
MAX9706 MAX9707
HPF LEFT IN CLASS D AMPLIFIER
LPF
CLASS D AMPLIFIER
RIGHT IN HPF CLASS D AMPLIFIER
Figure 1. Speaker Arrangement
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13
3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover MAX9706/MAX9707
Class D Speaker Amplifier
Spread-spectrum modulation and synchronizable switching frequency significantly reduce EMI emissions. Comparators monitor the audio inputs and compare the complementary input voltages to a sawtooth waveform. The comparators trip when the input magnitude 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, generating a minimumwidth pulse (tON(MIN),100ns typ) at the output of the second comparator (Figure 2). As the input voltage increases or decreases, the duration of the pulse at one output increases while the other output pulse duration remains the same. This causes the net voltage across the speaker (VOUT+ - VOUT-) to change. The minimum-width pulse helps the device to achieve high levels of linearity.
Operating Modes
Fixed-Frequency (FFM) Mode The MAX9706/MAX9707 feature two fixed-frequency modes. Connect SYNC_IN to GND to select a 1.1MHz switching frequency. Float SYNC to select a 1.34MHz switching frequency. The frequency spectrum of the MAX9706/MAX9707 consists of the fundamental switching frequency and its associated harmonics (see the Wideband Output Spectrum graph in the Typical Operating Characteristics). Program the switching frequency so the harmonics do not fall within a sensitive frequency band (Table 1). Audio reproduction is not affected by changing the switching frequency.
tSW
VIN-
VIN+
OUT-
OUT+
tON(MIN)
VOUT_+ - VOUT_-
Figure 2. Outputs with an Input Signal Applied (FFM Mode) 14 ______________________________________________________________________________________
3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover
Spread-Spectrum (SSM) Mode The MAX9706/MAX9707 feature a unique, patented spread-spectrum mode that flattens the wideband spectral components, improving EMI emissions that can be radiated by the speaker and cables. Enable SSM mode by setting SYNC_IN = VDD (Table 1). In SSM mode, the switching frequency varies randomly by 50kHz around the center frequency (1.15MHz). The modulation scheme remains the same, but the period of the sawtooth waveform changes from cycle to cycle (Figure 3). 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. A proprietary amplifier topology ensures this does not corrupt the noise floor in the audio bandwidth.
MAX9706/MAX9707
Table 1. Operating Modes
SYNC_IN GND FLOAT VDD Clocked MODE FFM with fOSC = 1100kHz FFM with fOSC = 1340kHz SSM with fOSC = 1150kHz 50kHz FFM with fOSC = external clock frequency
tSW
tSW
tSW
tSW
VIN_-
VIN_+
OUT_-
OUT_+
tON(MIN)
VOUT_+ - VOUT_-
Figure 3. Output with an Input Signal Applied (SSM Mode) ______________________________________________________________________________________ 15
3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover
External Clock Mode The SYNC_IN input allows the MAX9706/MAX9707 to be synchronized to an external clock, or another Maxim Class D amplifier. This creates a fully synchronous system, minimizing clock intermodulation, and allocating spectral components of the switching harmonics to insensitive frequency bands. Applying a TTL clock signal between 1MHz and 1.5MHz to SYNC_IN synchronizes the MAX9706/MAX9707. The period of the SYNC_IN clock can be randomized, allowing the MAX9706/MAX9707 to be synchronized to another Maxim Class D amplifier operating in SSM mode. SYNC_OUT allows several MAX9706/MAX9707s to be cascaded. The synchronized output minimizes any interference due to clock intermodulation caused by the switching spread between single devices. The modulation scheme remains the same when using SYNC_OUT, and audio reproduction is not affected. Leave SYNC_OUT floating if not used.
MAX9706/MAX9707
Efficiency
Efficiency loss of a Class D amplifier is due to the switching operation of the output stage transistors. In a Class D amplifier, the output transistors act as currentsteering switches and consume negligible additional power. Any power loss associated with the Class D output stage is mostly due to the I2R loss of the MOSFET on-resistance, and quiescent current overhead. The theoretical best efficiency of a Class AB 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 MAX9706/MAX9707 still exhibit >90% efficiencies under the same conditions (Figure 5).
Signal Path Gain
The MAX9706/MAX9707 feature four selectable speaker gain and two headphone gain settings controlled by two gain-control inputs GAIN1 and GAIN2 (see Table 2). Note that the stereo headphone output is full bandwidth, but the stereo speaker outputs are highpass filtered by the crossover circuitry.
Filterless Modulation/Common-Mode Idle
The MAX9706/MAX9707 use Maxim's unique, patented modulation scheme that eliminates the LC filter required by traditional Class D amplifiers, improving efficiency, reducing component count, conserving board space and system cost. Conventional Class D amplifiers output a 50% duty-cycle square wave when no signal is present. With no filter, the square wave appears across the load as a DC voltage, resulting in finite load current, increasing power consumption, especially when idling. When no signal is present at the input of the MAX9706/MAX9707, the outputs switch as shown in Figure 4. Because the MAX9706/MAX9707 drive the speaker differentially, the two outputs cancel each other, resulting in no net idle-mode voltage across the speaker, minimizing power consumption.
Table 2. Speaker Gain
GAIN2 0 0 1 1 GAIN1 0 1 0 1 SPEAKER GAIN (dB) +9 +10.5 +12 +13.5 MAX9706 HEADPHONE GAIN (dB) 0 0 +3 +3
100
VIN_ = 0V
90 80 EFFICIENCY (%) 70 60 50 40 30 VDD = 5V fIN = 1kHz RL = 8 0.8 1.0 1.2 MAX9706 POUT PER CHANNEL
OUT_-
OUT_+
20 10 0 0 0.2
CLASS AB TOTAL POUT 0.4 0.6
VOUT_+ - VOUT_- = 0V
OUTPUT POWER (W)
Figure 4. Outputs with No Input Signal 16
Figure 5. Efficiency vs. Class AB Efficiency
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3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover MAX9706/MAX9707
Table 3. Mono Speaker Gain
MGAIN GND FLOATING VDD MONO SPEAKER GAIN OFFSET (dB) -4.5 -7.5
AMPLITUDE (dB)
-6.0
HP FUNCTION 2nd-ORDER SLOPE
LP FUNCTION 2nd-ORDER SLOPE
Table 4. Crossover Frequency Selection
FS0 0 0 1 1 FS1 0 1 0 1 CROSSOVER FREQUENCY (fXO) (Hz) 800 1066.7 1600 2133.3
FREQUENCY (Hz) fX
Figure 6. Crossover Frequency
Mono Output
The left and right channels are summed and passed through a lowpass filter to generate the mono output. The mono speaker gain offset is an attenuation of the selected speaker gain. The MAX9706/MAX9707 offer three options for this summing gain. Select mono output gain by setting MGAIN high, low, or leave floating (see Table 3). The left- and right-speaker impedance should be twice that of the MONO channel (8 L/R, 4 MONO), then from the same voltage swing, the mono speaker will have 2 times the power. Over the left and right mono channels, a 1.5dB increase improves matching between the high- and low-frequency drivers.
Headphone Amplifier (MAX9706)
In conventional single-supply headphone amplifiers, the output-coupling capacitor is a major contributor of audible clicks and pops. Upon startup, the amplifier charges the coupling capacitor to its bias voltage, typically half the supply. Likewise, during shutdown, the capacitor is discharged to GND. This results in a DC shift across the capacitor, which in turn appears as an audible transient at the speaker. Since the MAX9706 headphone amplifier does not require output-coupling capacitors, no audible transients appear. The MAX9706 offers 0dB and 3dB headphone amplifier gain settings controlled through the GAIN2 gain-select input (see Table 2). DirectDrive Traditional single-supply headphone amplifiers have outputs biased at a nominal DC voltage (typically half the supply) for maximum dynamic range. Large coupling capacitors are needed to block this DC bias from the headphone. Without these capacitors, a 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 headphone outputs of the MAX9706 to be biased at GND, almost doubling dynamic range while operating from a single supply (Figure 7). With no DC component, there is no need for the large DC-blocking capacitors. Instead of two large
Crossover Frequency
The MAX9706/MAX9707 feature an internal active filter with adjustable crossover frequency (fXO) for use with a low-frequency transducer. The crossover filter consists of a complementary 2nd-order lowpass and 2nd-order highpass Butterworth filter (Figure 6). Crossover frequency is variable over the 800Hz to 2133.3Hz range to accommodate different speaker types. There are four selectable crossover frequencies selected by FS0 and FS1 (Table 4). The BTL outputs provide the option of phase-inverting the mono (LF) output with respect to the main (L/R) outputs. Depending on the speaker placement and distance from the listener, this can smooth the crossover transition between low and high frequencies.
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17
3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover MAX9706/MAX9707
(220F, typical) tantalum-blocking capacitors, the MAX9706 charge pump requires two small ceramic capacitors, conserving board space, reducing cost, and improving the frequency response of the headphone amplifier. See the Output Power vs. ChargePump Capacitance graph in the Typical Operating Characteristics for details on sizing charge-pump capacitors. There is a low DC voltage on the driver outputs due to amplifier offset. However, the offset of the MAX9706 is typically 1.7mV, which, when combined with a 32 load, results in less than 53A of DC current flow to the headphones. In addition to the cost and size disadvantages of the DC-blocking capacitors required by conventional headphone amplifiers, these capacitors limit the amplifier's low-frequency response and can distort the audio signal (Figure 8). Previous attempts at eliminating the output-coupling capacitors involved biasing the headphone return (sleeve) to the DC bias voltage of the headphone amplifiers. This method raises some issues: 1) The sleeve is typically grounded to the chassis. Using the midrail biasing approach, the sleeve must be isolated from system ground, complicating product design. During an ESD strike, the driver's ESD structures are the only path to system ground. Thus, the driver must be able to withstand the full ESD strike.
DirectDrive AMPLIFIER BIASING SCHEME VDD
VDD / 2
GND CONVENTIONAL AMPLIFIER BIASING SCHEME
+VDD
SGND
2)
When using the headphone jack as a line out to other equipment, the bias voltage on the sleeve may conflict with the ground potential from other equipment, resulting in possible damage to the drivers. Charge Pump The MAX9706 features a low-noise charge pump. The switching frequency of the charge pump is one-half the switching frequency of the Class D amplifier, regardless of the operating mode. When SYNC_IN is driven externally, the charge pump switches at 1/2 fSYNC_IN. When SYNC_IN = V DD , the charge pump switches with a spread-spectrum pattern. The nominal switching frequency is well beyond the audio range, and thus does not interfere with the audio signals, resulting in an SNR of 96dB. The switch drivers feature a controlled switching speed that minimizes noise generated by turn-on and turn-off transients. By limiting the switching speed of the charge pump, the di/dt noise caused by the parasitic bond wire and trace inductance is minimized. Although not typically required, additional high-frequency noise attenuation can be achieved by increasing the size of the charge-pump reservoir capacitor C2 (see the Functional Diagram/Typical Operating Circuits). The charge pump is active in both speaker and headphone modes.
18
-VDD
Figure 7. Traditional Amplifier Output vs. MAX9706 DirectDrive Output
0 -5 ATTENUATION (dB) -10 -15 -20 -25 -30 RL = 16 -35 10 100 FREQUENCY (Hz) 1000 DirectDrive 330F 220F 100F 33F
Figure 8. Low-Frequency Rolloff ______________________________________________________________________________________
3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover
Headphone Sense Input (HPS) The headphone sense input (HPS) monitors the headphone jack, and automatically configures the MAX9706 based upon the voltage applied at HPS. A voltage of less than 0.8V sets the MAX9706 to speaker mode and disables the headphone amplifiers. A voltage of greater than 2V disables the speaker amplifiers and enables the headphone amplifiers. The HPS input features a built-in 65ms debounce period to prevent audible "chatter" when inserting or removing headphones. For automatic headphone detection, connect HPS to the control pin of a 3-wire headphone jack as shown in Figure 9. With no headphone present, the output impedance of the headphone amplifier pulls HPS to less than 0.8V. When a headphone plug is inserted into the jack, the control pin is disconnected from the tip contact and HPS is pulled to VDD through the internal 600k pullup. When driving HPS from an external logic source, drive HPS low when the MAX9706 is shut down. Place a 10k resistor in series with HPS and the headphone jack to ensure high ESD protection.
Current Limit and Thermal Protection
The MAX9706/MAX9707 feature current limiting and thermal protection to protect the device from short circuits and overcurrent conditions. If the current on any output exceeds the current limit (1.5A typ) the internal circuitry shuts off for 50s then turns back on. If the overload condition is still present after 50s, the internal circuitry shuts off again. The amplifier output pulses in the event of a continuous overcurrent condition. The headphone amplifier outputs become high impedance in the event of an overcurrent condition. The speaker amplifier's current-limiting protection clamps the output current without shutting down the outputs. The MAX9706/MAX9707 feature thermal-shutdown protection with temperature hysteresis. A rising die temperature shuts down the device at +150C. When the die cools down to +143C, the device is enabled. The outputs pulsate as the temperature fluctuates between the thermal limits.
MAX9706/MAX9707
Shutdown
The MAX9706/MAX9707 feature a 0.1A shutdown mode that reduces power consumption to extend battery life. Driving SHDN low disables the drive amplifiers, bias circuitry, and charge pump and sets the headphone amplifier output impedance to 1.4k.
Click-and-Pop Suppression
The MAX9706/MAX9707 feature comprehensive clickand-pop suppression that eliminates audible transients on startup and shutdown. While in shutdown, the H-bridge is in a high-impedance state. 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.
Applications Information
Filterless Class D Operation
Traditional Class D amplifiers require an output filter to recover the audio signal from the amplifier's PWM output. The filters add cost, increase the solution size of the amplifier, and can decrease efficiency. The traditional PWM scheme uses large differential output swings (2 x VDD(P-P)) and causes large ripple currents. Any parasitic resistance in the filter components results in a loss of power, lowering the efficiency. The MAX9706/MAX9707 do not require an output filter. The devices rely on the inherent inductance of the speaker coil and the natural filtering of both the speaker 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 MAX9706/MAX9707 output 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 speaker not designed to handle the additional power can be damaged. For optimum results, use a speaker with a series inductance >10H. Typical 8 speakers for portable audio applications exhibit series inductances in the 20H to 100H range.
19
VDD MAX9706 600k SHUTDOWN CONTROL HPS HPL HPR 1.4k 1.4k
SHDN
Figure 9. HPS Configuration ______________________________________________________________________________________
3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover MAX9706/MAX9707
Power Supplies
The MAX9706/MAX9707 have different supplies for each portion of the devices, allowing for the optimum combination of headroom power dissipation and noise immunity. The speaker amplifiers are powered from PVDD. PVDD can range from 4.5V to 5.5V and must be connected to the same potential as VDD. The headphone amplifiers are powered from HPVDD and VSS. HPVDD is the positive supply of the headphone amplifiers and can range from 3V to 5.5V. VSS is the negative supply of the headphone amplifiers. Connect VSS to CPV SS . The charge pump is powered by CPV DD . Connect CPV DD to V DD for normal operation. The charge pump inverts the voltage at CPVDD, and the resulting voltage appears at CPVSS. The remainder of the device is powered by VDD.
Supply Bypassing, Layout, and Grounding
Proper layout and grounding are essential for optimum performance. Use large traces for the power-supply inputs and amplifier outputs to minimize losses due to parasitic trace resistance. Large traces also aid in moving heat away from the package. Proper grounding improves audio performance, minimizes crosstalk between channels, and prevents any switching noise from coupling into the audio signal. Connect PGND and GND together at a single point on the PC board (star configuration). Route all traces that carry switching transients away from GND and the traces/components in the audio signal path. Connect the power-supply inputs V DD and PV DD together and connect CPV DD and HPV DD together. Bypass HPVDD and CPVDD with a 1F capacitor in parallel with a 0.1F capacitor to PGND. Bypass VDD and PVDD with a 1F capacitor to GND. Place the bypass capacitors as close to the device as possible. Place a bulk capacitor between PVDD and PGND if needed. Use large, low-resistance output traces. Current drawn from the outputs increase as load impedance decreases. High-output trace resistance decreases the power delivered to the load. Large output, supply, and GND traces allow more heat to move from the device to the air, decreasing the thermal impedance of the circuit if possible or connect to VSS. The MAX9706/MAX9707 thin QFN-EP package features an exposed thermal pad on its underside. This pad lowers the package's thermal impedance by providing a direct heat conduction path from the die to the PC board. The exposed thermal pad is not internally connected. Connect the exposed pad to GND. BIAS Capacitor BIAS is the output of the internally generated DC bias voltage. The BIAS bypass capacitor, CBIAS improves PSRR and THD+N by reducing power supply and other noise sources at the common-mode bias node, and also generates the clickless/popless, startup/shutdown DC bias waveforms for the speaker amplifiers. Bypass BIAS with a 1F capacitor to GND.
Component Selection
Input Filter An input capacitor, CIN, in conjunction with the input impedance of the MAX9706/MAX9707 forms a highpass filter that removes the DC bias from an incoming signal. The AC-coupling capacitor allows the amplifier to automatically bias the signal to an optimum DC level. Assuming zero-source impedance, the -3dB point of the highpass filter is given by: f-3dB = 1 2 x RIN x CIN
Choose CIN so f-3dB is well below the lowest frequency of interest. Use capacitors whose dielectrics have low-voltage coefficients, such as tantalum or aluminum electrolytic. Capacitors with high-voltage coefficients, such as ceramics, may result in increased distortion at low frequencies.
Crossover Selection
Select the crossover filter to suit the chosen speaker. Many small diameter speakers (as used in notebooks and smaller displays) are self resonant (fO) at 800Hz to 1000Hz. Often these speakers have a slight peaking at resonance, so choosing a crossover frequency at 2 x fO can be effective. Ensure the mono channel speaker has its fO much lower than crossover frequency (fC).
20
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3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover MAX9706/MAX9707
Table 5. Suggested Capacitor Manufacturers
SUPPLIER Taiyo Yuden TDK PHONE 800-348-2496 807-803-6100 FAX 847-925-0899 847-390-4405 WEBSITE www.t-yuden.com www.component.tdk.com
Charge-Pump Capacitor Selection (MAX9706) Use capacitors with an ESR less than 100m for optimum performance. Low-ESR ceramic capacitors minimize the output resistance of the charge pump. Most surface-mount ceramic capacitors satisfy the ESR requirement. For best performance over the extended temperature range, select capacitors with an X7R dielectric. Table 5 lists suggested manufacturers. Flying Capacitor (C1, MAX9706) The value of the flying capacitor (C1) affects the output resistance of the charge pump. A C1 value that is too small degrades the device's ability to provide sufficient current drive, which leads to a loss of output voltage. Increasing the value of C1 reduces the charge-pump output resistance to an extent. Above 1F, the on-resistance of the switches and the ESR of C1 and C2 dominate.
Output Capacitor (C2, MAX9706) The output capacitor value and ESR directly affect the ripple at CPVSS. Increasing the value of C2 reduces output ripple. Likewise, decreasing the ESR of C2 reduces both ripple and output resistance. Lower capacitance values can be used in systems with low maximum output power levels. See the Output Power vs. Charge-Pump Capacitance and Load Resistance graph in the Typical Operating Characteristics. C2 must be equal to or greater than C1. CPVDD Bypass Capacitor (MAX9706) The CPVDD bypass capacitor lowers the output impedance of the power supply and reduces the impact of the MAX9706's charge-pump switching transients. Bypass CPVDD with a capacitor to CPGND and place it physically close to CPVDD and CPGND. Use a value that is equal to C1.
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21
3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover MAX9706/MAX9707
Functional Diagram/Typical Operating Circuits
4.5V TO 5.5V
CBIAS 1F
1F
10F*
1F
BIAS 1 BIAS GENERATOR VDD SYNC_IN 14 CIN 0.47F INL 36
VDD 3
PVDD 8, 20, 34
MAX9706
4 SYNC_OUT
OSCILLATOR AND SAWTOOTH CLASS D MODULATOR AND H-BRIDGE
7 OUTL+ 6 OUTL-
LOWPASS/ HIGHPASS FILTER
MGAIN 28
CLASS D MODULATOR AND H-BRIDGE
33 OUTM+ 32 OUTM-
CIN 0.47F INR 27 SHDN 24 FS1 26 FS0 25 GAIN1 30 GAIN2 29 HPVDD 19 CPVDD 9 C1P 10 1F 0.1F C1 1F C1N 12 CPGND 11
LOWPASS/ HIGHPASS FILTER HPVDD
CLASS D MODULATOR AND H-BRIDGE
21 OUTR+ 22 OUTR-
CONTROL INL
15 HPS 18 HPL
CHARGE PUMP
INR
17 HPR
35 MONO_OUT
13 CPVSS C2 1F
16 VSS
2 GND
5, 23, 31 PGND
*BULK CAPACITANCE IF NEEDED TYPICAL OPERATING CIRCUIT SHOWN DEPICTS THE MAX9706 WITH: SSM MODE WITH fOSC = 1150kHz, SPEAKER GAIN = +9dB, MONO SPEAKER GAIN OFFSET = -6.0dB, HEADPHONE SPEAKER GAIN = +0dB, AND CROSSOVER FREQUENCY = 1066.7Hz.
22
______________________________________________________________________________________
3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover
Functional Diagram/Typical Operating Circuits (continued)
4.5V TO 5.5V
MAX9706/MAX9707
1F
10F*
1F
VDD 3 VDD
PVDD 8, 20, 34
MAX9707
SYNC_IN 14 CIN 0.47F INL 36 OSCILLATOR AND SAWTOOTH CLASS D MODULATOR AND H-BRIDGE 4 SYNC_OUT
7 OUTL+ 6 OUTL-
LOWPASS/ HIGHPASS FILTER
MGAIN 28
CLASS D MODULATOR AND H-BRIDGE
33 OUTM+ 32 OUTM-
CIN 0.47F INR 27 SHDN 24 FS1 26 FS0 25 GAIN1 30 GAIN2 29
LOWPASS/ HIGHPASS FILTER
CLASS D MODULATOR AND H-BRIDGE
21 OUTR+ 22 OUTR-
CONTROL 35 MONO_OUT BIAS GENERATOR 15 I.C. 9 N.C. 10 N.C. 11 N.C.
12
13
16
17
18
19
1 BIAS
2 GND
5, 23, 31 PGND
N.C. N.C. N.C. N.C. N.C. N.C. CBIAS 1F
*BULK CAPACITANCE IF NEEDED TYPICAL OPERATING CIRCUIT SHOWN DEPICTS THE MAX9707 WITH: SSM MODE WITH fOSC = 1150kHz, SPEAKER GAIN = +9dB, MONO SPEAKER GAIN OFFSET = -6.0dB, AND CROSSOVER FREQUENCY = 1066.7Hz.
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23
3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover MAX9706/MAX9707
Pin Configurations
SHDN PGND OUTROUTR+ PVDD HPVDD TOP VIEW TOP VIEW SHDN PGND OUTROUTR+ PVDD N.C. 18 17 16 15 14 13 12 11 10 1 BIAS 2 GND 3 4 5 6 7 8 PVDD 9 N.C.
FS1 FS0
INR
27 26 25 24 23 22 21 20 19 MGAIN GAIN2 GAIN1 PGND OUTMOUTM+ PVDD MONO_OUT INL 28 29 30 31 32 33 34 35 36 1 BIAS 2 3 4 5 6 7 8 PVDD 9 CPVDD 18 17 16 15 14 13 12 11 10 HPL HPR VSS HPS SYNC_IN CPVSS C1N CPGND C1P MGAIN GAIN2 GAIN1 PGND OUTMOUTM+ PVDD MONO_OUT INL 28 29 30 31 32 33 34 35 36
INR
27 26 25 24 23 22 21 20 19 N.C. N.C. N.C. I.C. SYNC_IN N.C. N.C. N.C. N.C.
MAX9706
FS1 FS0
MAX9707
GND VDD SYNC_OUT PGND OUTLOUTL+
6mm x 6mm TQFN
6mm x 6mm TQFN
TRANSISTOR COUNT: 12,686 PROCESS: BICMOS
24
______________________________________________________________________________________
VDD SYNC_OUT PGND OUTLOUTL+
Chip Information
3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)
MAX9706/MAX9707
E E/2
(NE-1) X e
k D/2
D
(ND-1) X e D2/2 e b E2/2 k
C L
C L
D2
L
E2
e L
C L C L
L1 L e e L
A1
A2
A
PACKAGE OUTLINE 36, 40, 48L THIN QFN, 6x6x0.8mm
21-0141
F
1
2
NOTES: 1. DIMENSIONING & TOLERANCING CONFORM TO ASME Y14.5M-1994. 2. ALL DIMENSIONS ARE IN MILLIMETERS. ANGLES ARE IN DEGREES. 3. N IS THE TOTAL NUMBER OF TERMINALS. 4. THE TERMINAL #1 IDENTIFIER AND TERMINAL NUMBERING CONVENTION SHALL CONFORM TO JESD 95-1 SPP-012. DETAILS OF TERMINAL #1 IDENTIFIER ARE OPTIONAL, BUT MUST BE LOCATED WITHIN THE ZONE INDICATED. THE TERMINAL #1 IDENTIFIER MAY BE EITHER A MOLD OR MARKED FEATURE. 5. DIMENSION b APPLIES TO METALLIZED TERMINAL AND IS MEASURED BETWEEN 0.25 mm AND 0.30 mm FROM TERMINAL TIP. 6. ND AND NE REFER TO THE NUMBER OF TERMINALS ON EACH D AND E SIDE RESPECTIVELY. 7. DEPOPULATION IS POSSIBLE IN A SYMMETRICAL FASHION. 8. COPLANARITY APPLIES TO THE EXPOSED HEAT SINK SLUG AS WELL AS THE TERMINALS. 9. DRAWING CONFORMS TO JEDEC MO220, EXCEPT FOR 0.4mm LEAD PITCH PACKAGE T4866-1. 10. WARPAGE SHALL NOT EXCEED 0.10 mm. 11. MARKING IS FOR PACKAGE ORIENTATION REFERENCE ONLY. 12. NUMBER OF LEADS SHOWN FOR REFERENCE ONLY.
PACKAGE OUTLINE 36, 40, 48L THIN QFN, 6x6x0.8mm
21-0141
F
2
2
The MAX9706/MAX9707 Thin QFN-EP package features an exposed thermal pad on its underside. This pad lowers the package's thermal impedance by providing a direct heat conduction path from the die to the printed circuit board. The exposed thermal pad is not internally connected. Connect the exposed pad to GND.
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 ____________________ 25 (c) 2005 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products, Inc.
QFN THIN.EPS

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