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19-3691; Rev 0; 5/05
3.2W, High-Efficiency, Low-EMI, Filterless, Class D Audio Amplifier
General Description
The MAX9759 mono class D, audio power amplifier provides class AB amplifier audio performance with the benefits of class D efficiency, eliminating the need for a heatsink and extending battery life. The MAX9759 delivers up to 3.2W of continuous power into a 4 load while offering greater than 90% efficiency. Maxim's next-generation, low-EMI modulation scheme allows the amplifier to operate without an external LC filter while still meeting FCC EMI-radiated emission levels. The MAX9759 offers two modulation schemes: a fixedfrequency modulation (FFM) mode and a spread-spectrum modulation (SSM) mode. The SSM mode flattens the wideband spectral components, reducing EMI-radiated emissions due to the modulation frequency. Furthermore, the MAX9759 oscillator can be synchronized to an external clock through the SYNC input, allowing the switching frequency to range from 1000kHz to 1600kHz. The SYNC input and SYNC_OUT output of the MAX9759 allow multiple Maxim class D amplifiers to be cascaded and frequency locked, minimizing interference due to clock intermodulation. The MAX9759 utilizes fully differential input amplifiers, a fullbridged output, comprehensive click-and-pop suppression, and features four selectable gain settings (6dB, 12dB, 18dB, 24dB). The MAX9759 features high 81dB PSRR, low 0.02% THD+N, and SNR in excess of 90dB. Short-circuit and thermal-overload protection prevents damage to the device during a fault condition. The MAX9759 operates from a single 5V supply, consumes 8.4mA of supply current, and is available in a 16-pin thin QFN package (4mm x 4mm x 0.8mm) and a 16-pin TSSOP package. The MAX9759 is fully specified over the extended -40C to +85C temperature range. 3.2W into 4 Load (THD+N = 10%) Filterless Amplifier Passes FCC Radiated Emissions Standards with 7.6cm of Cable 92% Efficiency High PSRR (81dB at 1kHz) Low 0.02% THD+N External Clock Synchronization for Multiple, Cascaded Maxim Class D Amplifiers 3.0V to 5.5V Single-Supply Operation Pin-Selectable Gain (6dB, 12dB, 18dB, 24dB) Integrated Click-and-Pop Suppression Low Quiescent Current (8.4mA) Low-Power Shutdown Mode (10A) Mute Function Short-Circuit and Thermal-Overload Protection Available in Thermally Efficient Packages 16-Pin TQFN (4mm x 4mm x 0.8mm) 16-Pin TSSOP
Features
MAX9759
Ordering Information
PART MAX9759ETE+ MAX9759EUE+ TEMP RANGE -40C to +85C -40C to +85C PIN-PACKAGE 16 TQFN-EP* 16 TSSOP
+Denotes lead-free package. *EP = Exposed paddle.
Simplified Block Diagram
VDD
Applications
Cell Phones/PDAs Notebook PCs Portable DVD Players Flat-Panel PC Monitors LCD TVs LCD Projectors
SYNC INPUT SYNC OUTPUT OSCILLATOR DIFFERENTIAL AUDIO INPUT
MODULATOR AND H-BRIDGE
MONO SPEAKER OUTPUT
GAIN CONTROL SHDN CONTROL
G1 G2 SHDN MUTE
MAX9759
MUTE CONTROL
Pin Configurations appear at end of data sheet. ________________________________________________________________ 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.
3.2W, High-Efficiency, Low-EMI, Filterless, Class D Audio Amplifier MAX9759
ABSOLUTE MAXIMUM RATINGS
VDD to GND..............................................................................6V PVDD to PGND .........................................................................6V GND to PGND .......................................................-0.3V to +0.3V All Other Pins to GND.................................-0.3V to (VDD + 0.3V) Continuous Current Into/Out of PVDD/PGND/OUT+/OUT-....1.7A Duration of OUT+ or OUT- Short Circuit to VDD/GND/PVDD/PGND............................................Continuous Duration of Short Circuit Between OUT+ and OUT- ..Continuous Continuous Power Dissipation (TA = +70C) 16-Pin TQFN (derate 16.9mW/C above +70C) .....1349.1mW 16-Pin TSSOP (derate 9.4mW/C above +70C) .......754.7mW Junction Temperature ......................................................+150C Operating Temperature Range ...........................-40C to +85C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C ESD Protection (+IBM).........................................................2kV
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 = 5.0V)
(VDD = PVDD = SHDN = MUTE = 5V, GND = PGND = 0V, SYNC = 0V (FFM). Gain = 12dB (G1 = 0, G2 = 1). Speaker load resistor (RL) connected between OUT+ and OUT-, unless otherwise noted, RL = , TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) (Notes 1, 2)
PARAMETER GENERAL Supply Voltage Range Quiescent Current Mute Current Shutdown Current Shutdown to Full Operation Mute to Full Operation Common-Mode Rejection Ratio Input DC Bias Voltage VDD IDD IMUTE IDD(SHDN) tSON tMUTE CMRR VCM Gain = +24dB Input Resistance RIN Gain = +18dB Gain = +12dB Gain = +6dB G1 = 0, G2 = 0 Voltage Gain AV G1 = 1, G2 = 0 G1 = 0, G2 = 1 G1 = 1, G2 = 1 Output Offset Voltage VOS TA = +25C VDD = 4.5V to 5.5V Power-Supply Rejection Ratio (Note 3) PSRR fRIPPLE = 217Hz 200mVP-P ripple fRIPPLE = 1kHz fRIPPLE = 20kHz 62 f = 1kHz, input referred, VIN = 200mVP-P 1.3 14 25 40 60 +22 +16 +10 +4 Inferred from PSRR test No load V MUTE = 0V V SHDN = 0V 3.0 8.4 5.5 0.1 40 40 67 1.5 20 36 60 90 +24 +18 +12 +6 10 90 79 81 70 dB 1.7 26 47 80 120 +26 +20 +14 +8 50 mV dB k 5.5 12 8 10 V mA mA A ms ms dB V SYMBOL CONDITIONS MIN TYP MAX UNITS
2
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3.2W, High Efficiency, Low-EMI, Filterless, Class D Audio Amplifier
ELECTRICAL CHARACTERISTICS (VDD = 5.0V) (continued)
(VDD = PVDD = SHDN = MUTE = 5V, GND = PGND = 0V, SYNC = 0V (FFM). Gain = 12dB (G1 = 0, G2 = 1). Speaker load resistor (RL) connected between OUT+ and OUT-, unless otherwise noted, RL = , TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) (Notes 1, 2)
PARAMETER SYMBOL THD+N = 1% Output Power POUT THD+N = 10% CONDITIONS RL = 3 RL = 4 RL = 8 RL = 3 RL = 4 RL = 8 Total Harmonic Distortion Plus Noise THD+N fIN = 1kHz, either FFM or SSM, POUT = 1W RL = 3 RL = 4 RL = 8 FFM SSM FFM SSM 1000 1102 MIN TYP 3.4 2.6 1.4 4.3 3.2 1.8 0.08 0.05 0.02 93 89 96 92 1100 1500 1200 70 1000 -50 dB Out of shutdown -57 92 % 1600 kHz 1200 1837 kHz dB % W MAX UNITS
MAX9759
Signal-to-Noise Ratio
SNR
POUT = 1W, RL = 8
BW = 22Hz to 22kHz A-weighted
SYNC = GND (FFM mode) Oscillator Frequency fOSC SYNC = FLOAT (FFM mode) SYNC = VDD (SSM mode) SYNC Frequency Lock Range Click-and-Pop Level KCP TTL-compatible clock input Peak voltage, A-weighted, 32 samples per second (Notes 3, 4) Into shutdown
Efficiency
POUT = 1W, fIN = 1kHz, RL = 8 in series with 68H VDD x 0.9
DIGITAL INPUTS (SHDN, MUTE, G1, G2, SYNC) SYNC, G1, G2 Input Voltage High SYNC, G1, G2 Input Voltage Low SHDN, MUTE Voltage High SHDN, MUTE Voltage Low SYNC Input Resistance SYNC Input Current SHDN, MUTE, G1, G2 Input Current SYNC Capacitance DIGITAL OUTPUTS (SYNC_OUT) Output Voltage High Output Voltage Low SYNC_OUT Capacitive Drive VOH VOL IOH = 3mA IOL = 3mA TTL-compatible clock output 100 2.4 0.4 V V pF VINH VINL VINH VINL 200 35 1 10 2 0.8 V VDD x 0.1 V V V k A A pF
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3
3.2W, High-Efficiency, Low-EMI, Filterless, Class D Audio Amplifier MAX9759
ELECTRICAL CHARACTERISTICS (VDD = 3.3V)
(VDD = PVDD = SHDN = MUTE = 3.3V, GND = PGND = 0V, SYNC = GND (FFM). Gain = 12dB (G1 = 0, G2 = 1). Speaker load resistor (RL) connected between OUT+ and OUT-, unless otherwise noted. RL = , TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) (Notes 1, 2)
PARAMETER Quiescent Current Mute Current Shutdown Current Common-Mode Rejection Ratio SYMBOL IDD IMUTE ISHDN CMRR V MUTE = 0V V SHDN = 0V f = 1kHz, input referred VDD = 3.0V to 5.5V Power-Supply Rejection Ratio PSRR fRIPPLE = 217Hz 200mVP-P ripple fRIPPLE = 1kHz fRIPPLE = 20kHz RL = 3 THD+N = 1% Output Power POUT THD+N = 10% RL = 4 RL = 8 RL = 3 RL = 4 RL = 8 Total Harmonic Distortion Plus Noise THD+N f = 1kHz, either FFM or SSM, POUT = 500mW RL = 3 RL = 4 RL = 8 BW = 22Hz to 22kHz A-weighted FFM SSM FFM SSM 50 CONDITIONS MIN TYP 6 5 0.1 67 72 79 81 70 1.5 1.1 0.65 1.8 1.3 0.78 0.06 0.04 0.02 93 89 96 92 dB % W MAX UNITS mA A A dB dB dB
Signal-to-Noise Ratio
SNR
POUT = 500mW, RL = 8
Note 1: All devices are 100% production tested at +25C. 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 = 4, L = 33H. For RL = 8, L = 68H. Note 3: Inputs AC-coupled to GND. Note 4: Testing performed with 8 resistive load in series with a 68H inductive load across BTL outputs. Mode transitions are controlled by the SHDN pin.
4
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3.2W, High-Efficiency, Low-EMI, Filterless, Class D Audio Amplifier MAX9759
Typical Operating Characteristics
(VDD = PVDD = SHDN = MUTE = 5V, GND = PGND = 0V, SYNC = VDD (SSM), unless otherwise noted. Gain = 12dB (G1 = 0, G2 = 1). THD+N measurement bandwidth: 22Hz to 22kHz. Typical values are at TA = +25C.) (See Typical Operating Circuit)
TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY
MAX9759 toc01
TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY
MAX9759 toc02
TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY
VDD = 5V RL = 4 1 THD+N (%)
MAX9759 toc03
10 VDD = 5V RL = 3 1 THD+N (%)
10 VDD = 3.3V RL = 3 1 THD+N (%)
10
POUT = 1W 0.1
POUT = 500mW 0.1
POUT = 1W 0.1
0.01
POUT = 2.6W
0.01
POUT = 1.3W
0.01
POUT = 2.2W
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
MAX9759 toc04
TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY
MAX9759 toc05
TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY
VDD = 3.3V RL = 8 1 THD+N (%)
MAX9759 toc06
10 VDD = 3.3V RL = 4 1 THD+N (%) POUT = 500mW 0.1
10 VDD = 5V RL = 8 1 THD+N (%)
10
0.1
POUT = 600mW
0.1
POUT = 300mW
0.01
POUT = 700mW
0.01 POUT = 1.2W
0.01 POUT = 500mW 0.001 10 100 1k FREQUENCY (Hz) 10k 100k 10 100 1k FREQUENCY (Hz) 10k 100k
0.001 10 100 1k FREQUENCY (Hz) 10k 100k
0.001
TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY
MAX9759 toc07
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
MAX9759 toc08
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
VDD = 3.3V RL = 3
MAX9759 toc09
10 VDD = 5V RL = 8 POUT = 1.2W 1 THD+N (%)
100 VDD = 5V RL = 3 10
100
10
THD+N (%)
THD+N (%)
1
0.1
fIN = 200Hz, 1kHz
1 fIN = 200Hz, 1kHz 0.1 fIN = 10kHz
SSM
0.1
0.01 FFM 0.001 10 100 1k FREQUENCY (Hz) 10k 100k 0.01
fIN = 10kHz
0.01
0.001 0 1 2 3 4 OUTPUT POWER (W)
0.001 0 0.5 1.0 OUTPUT POWER (W) 1.5 2.0
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5
3.2W, High-Efficiency, Low-EMI, Filterless, Class D Audio Amplifier MAX9759
Typical Operating Characteristics (continued)
(VDD = PVDD = SHDN = MUTE = 5V, GND = PGND = 0V, SYNC = VDD (SSM), unless otherwise noted. Gain = 12dB (G1 = 0, G2 = 1). THD+N measurement bandwidth: 22Hz to 22kHz. Typical values are at TA = +25C.) (See Typical Operating Circuit)
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
MAX9759 toc10
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
MAX9759 toc11
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
VDD = 5V RL = 8 10
MAX9759 toc12
100 VDD = 5V RL = 4 10
100 VDD = 3.3V RL = 4 10
100
THD+N (%)
THD+N (%)
1 fIN = 200Hz, 1kHz 0.1 fIN = 10kHz 0.01
1
THD+N (%)
fIN = 200Hz, 1kHz
1 fIN = 200Hz, 1kHz 0.1 fIN = 10kHz
0.1 fIN = 10kHz
0.01
0.01
0.001 0 1 2 3 OUTPUT POWER (W)
0.001 0 0.5 1.0 1.5 OUTPUT POWER (W)
0.001 0 0.5 1.0 OUTPUT POWER (W) 1.5 2.0
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
MAX9759 toc13
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
VDD = 5V fIN = 1kHz RL = 8
MAX9759 toc14
EFFICIENCY vs. OUTPUT POWER
90 80 EFFICIENCY (%) 70 60 50 40 30 RL = 8 RL = 4 RL = 3
MAX9759 toc15
100 VDD = 3.3V RL = 8 10
100
100
10
THD+N (%)
1 fIN = 200Hz, 1kHz
THD+N (%)
1 f = 1180kHz, FFM 0.1
0.1
0.01 fIN = 10kHz 0.001 0 0.2 0.4 OUTPUT POWER (W) 0.6 0.8
0.01 f = 1400kHz, FFM 0.001 0 0.5 1.0 OUTPUT POWER (W) 1.5 2.0
20 10 0 0 1 2 3 4 5 OUTPUT POWER (W) VDD = 5V fIN = 1kHz
EFFICIENCY vs. OUTPUT POWER
MAX9759 toc16
EFFICIENCY vs. SUPPLY VOLTAGE
MAX9759 toc17
OUTPUT POWER vs. SUPPLY VOLTAGE
RL = 3 fIN = 1kHz
MAX9759 toc18
100 90 80 EFFICIENCY (%) 70 60 50 40 30 20 10 0 0 0.5 1.0 OUTPUT POWER (W) 1.5 VDD = 3.3V fIN = 1kHz RL = 8 RL = 4 RL = 3
100 90 80 EFFICIENCY (%) 70 60 50 40 30 fIN = 1kHz THD+N = 1% 3.0 3.5 5.0 4.5 SUPPLY VOLTAGE (V) 4.0 RL = 8 RL = 4
6 5 OUTPUT POWER (W) 4 3 2 THD+N = 1% 1 0
THD+N = 10%
2.0
5.5
3.0
3.5
4.0 4.5 5.0 SUPPLY VOLTAGE (V)
5.5
6
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3.2W, High Efficiency, Low-EMI, Filterless, Class D Audio Amplifier MAX9759
Typical Operating Characteristics (continued)
(VDD = PVDD = SHDN = MUTE = 5V, GND = PGND = 0V, SYNC = VDD (SSM), unless otherwise noted. Gain = 12dB (G1 = 0, G2 = 1). THD+N measurement bandwidth: 22Hz to 22kHz. Typical values are at TA = +25C.) (See Typical Operating Circuit)
OUTPUT POWER vs. SUPPLY VOLTAGE
MAX9759 toc19
OUTPUT POWER vs. SUPPLY VOLTAGE
RL = 8 fIN = 1kHz 2.0 OUTPUT POWER (W) THD+N = 10% 1.5
MAX9759 toc20
4.0 3.5 OUTPUT POWER (W) 3.0 THD+N = 10% 2.5 2.0 1.5 1.0 THD+N = 1% RL = 4 fIN = 1kHz
2.5
1.0 THD+N = 1% 0.5
0.5 0 3.0 3.5 4.0 4.5 5.0 5.5 SUPPLY VOLTAGE (V) 0 3.0 3.5 4.0 4.5 5.0 5.5 SUPPLY VOLTAGE (V)
OUTPUT POWER vs. LOAD RESISTANCE
MAX9759 toc21
OUTPUT POWER vs. LOAD RESISTANCE
1.8 1.6 OUTPUT POWER (W) 1.4 1.2 1.0 0.8 0.6 0.4 1% THD+N 1 10 LOAD RESISTANCE () 100 10% THD+N VDD = 3.3V fIN = 1kHz
MAX9759 toc22
5.0 4.5 4.0 OUTPUT POWER (W) 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 1 10 LOAD RESISTANCE () 1% THD+N 10% THD+N VDD = 5V fIN = 1kHz
2.0
0.2 0 100
TOTAL HARMONIC DISTORTION PLUS NOISE vs. COMMON-MODE VOLTAGE
MAX9759 toc23
TOTAL HARMONIC DISTORTION PLUS NOISE vs. COMMON-MODE VOLTAGE
VDD = 5V 3.3V RL = 8 fIN = 1kHz POUT = 300mW DIFF INPUT
MAX9759 toc24
100 VDD = 5V RL = 8 fIN = 1kHz POUT = 300mW DIFF INPUT
100
10
10
THD+N (%)
THD+N (%) 0 1 2 3 4
1
1
0.1
0.1
0.01
0.01
0.001 COMMON-MODE VOLTAGE (V)
0.001 0 1 2 3 4 COMMON-MODE VOLTAGE (V)
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7
3.2W, High-Efficiency, Low-EMI, Filterless, Class D Audio Amplifier MAX9759
Typical Operating Characteristics (continued)
(VDD = PVDD = SHDN = MUTE = 5V, GND = PGND = 0V, SYNC = VDD (SSM), unless otherwise noted. Gain = 12dB (G1 = 0, G2 = 1). THD+N measurement bandwidth: 22Hz to 22kHz. Typical values are at TA = +25C.) (See Typical Operating Circuit)
COMMON-MODE REJECTION RATIO vs. FREQUENCY
MAX9759 toc25
POWER-SUPPLY REJECTION RATIO vs. FREQUENCY
MAX9759 toc26
OUTPUT FREQUENCY SPECTRUM
FFM MODE VOUT = -60dBV fIN = 1kHz RL = 8 UNWEIGHTED
MAX9759 toc27
0 -10 -20 -30 CMRR (dB) INPUT REFERRED VIN = 200mVP-P
0 -10 -20 -30 PSRR (dB) -40 -50 -60 -70 -80 -90 -100 OUTPUT REFERRED INPUTS AC GROUNDED
0 -20 OUTPUT MAGNITUDE (dBV) -40 -60 -80 -100 -120 -140
-40 -50 -60 -70 -80 -90 -100 10 100 1k FREQUENCY (Hz) 10k 100k
10
100
1k FREQUENCY (Hz)
10k
100k
0
5k
10k FREQUENCY (Hz)
15k
20k
OUTPUT FREQUENCY SPECTRUM
MAX9759 toc28
WIDEBAND OUTPUT SPECTRUM (FFM MODE)
MAX9759 toc29
WIDEBAND OUTPUT SPECTRUM (SSM MODE)
30 OUTPUT AMPLITUDE (dBV) 20 10 0 -10 -20 -30 -40 -50 -60 RBW = 10kHz
MAX9759 toc30
0 -20 OUTPUT MAGNITUDE (dBV) -40 -60 -80 -100 -120 -140 0 5k 10k FREQUENCY (Hz) 15k SSM MODE VOUT = -60dBV fIN = 1kHz RL = 8 UNWEIGHTED
40 30 OUTPUT AMPLITUDE (dBV) 20 10 0 -10 -20 -30 -40 -50 -60 RBW = 10kHz
40
20k
1M
10M
100M
1000M
1M
10M
100M
1000M
FREQUENCY (Hz)
FREQUENCY (Hz)
SHUTDOWN RESPONSE
MAX9759 toc31
MUTE RESPONSE
MAX9759 toc32
SHDN
5V
MUTE
5V
0V
0V
MAX9759 OUTPUT f = 1kHz RL = 8 20ms/div
500mV/div
MAX9759 OUTPUT f = 1kHz RL = 8 20ms/div
500mV/div
8
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3.2W, High-Efficiency, Low-EMI, Filterless, Class D Audio Amplifier MAX9759
Typical Operating Characteristics (continued)
(VDD = PVDD = SHDN = MUTE = 5V, GND = PGND = 0V, SYNC = VDD (SSM), unless otherwise noted. Gain = 12dB (G1 = 0, G2 = 1). THD+N measurement bandwidth: 22Hz to 22kHz. Typical values are at TA = +25C.) (See Typical Operating Circuit)
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX9759 toc33
SHUTDOWN SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX9759 toc34
PACKAGE TEMPERATURE vs. TIME
MAX9759 toc35
9.0 8.5 SUPPLY CURRENT (mA) 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 3.0
0.20 0.18 0.16 SUPPLY CURRENT (A) 0.14 0.12 0.10 0.08 0.06 0.04 0.02 0 TA = -40C TA = +25C FFM TA = +85C
FFM TA = +85C TA = +25C
60 50 RL = 3 AT 10% THD+N 40 30 20 10 0 RL = 4 AT 10% THD+N
TA = -40C
PACKAGE TEMPERATURE (C)
RL = 8 AT 10% THD+N MAX9759EVKIT FREE AIR TA = +25C fIN = 1kHz SINE WAVE 0 50 100 150 TIME (s) 200 250 300
3.5
4.0
4.5
5.0
5.5
4.5
4.7
4.9
5.1
5.3
5.5
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
Typical Operating Circuit/Functional Diagram
VDD
8 (14) MUTE 16 (6) G1 G2 15 (5) 2 (8) IN+ 3 (9) INRIN CONTROL
10F* 5 (11) SHDN
1F 1 (7) VDD 9, 12 (2, 15) PVDD CLICK-AND-POP SUPPRESSION PVDD
UVLO/POWER MANAGEMENT
VDD GND
RF 11 OUT+ (1) CLASS D MODULATOR PVDD OUT- 10 (16)
1F
1F
RIN BIAS RF
7 (13) SYNC
OSCILLATOR
MAX9759
13 SYNC_OUT (3) PGND GND 4 (10)
( ) TSSOP
6, 14 (4, 12)
NOTE: TYPICAL OPERATING CIRCUIT DEPICTS MAX9759 IN FFM MODE WITH fS = 1400kHz and +18dB OF GAIN.
*BULK CAPACITANCE, IF NEEDED.
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3.2W, High-Efficiency, Low-EMI, Filterless, Class D Audio Amplifier MAX9759
Pin Description
PIN TQFN 1 2 3 4 5 6, 14 TSSOP 7 8 9 10 11 4, 12 NAME VDD IN+ INGND SHDN PGND FUNCTION Analog Power Supply. Bypass to GND with a 1F ceramic capacitor. Noninverting Audio Input Inverting Audio Input Analog Ground Active-Low Shutdown Input. Drive SHDN low to shut down the MAX9759. Connect to VDD for normal operation. Power Ground Frequency Select and External Clock Input: SYNC = GND: Fixed-frequency mode with fS = 1100kHz. SYNC = FLOAT: Fixed-frequency mode with fS = 1500kHz. SYNC = VDD: Spread-spectrum mode with fS = 1200kHz 70kHz. SYNC = Clocked: Fixed-frequency mode with fS = external clock frequency. Active-Low Mute Function. Drive MUTE low to disable the H-bridge outputs. Connect to VDD for normal operation. H-Bridge Power Supply. Bypass to PGND with a 10F ceramic capacitor. Negative Speaker Output Positive Speaker Output Internal Clock Output. Connect SYNC_OUT to the clock input of cascaded Maxim class D amplifiers. Float SYNC_OUT if unused. Gain Control 2 (See the Gain Selection Section) Gain Control 1 (See the Gain Selection Section) Exposed Paddle. Can be left floating or tied to GND.
7
13
SYNC
8 9, 12 10 11 13 15 16 EP
14 2, 15 16 1 3 5 6 EP
MUTE PVDD OUTOUT+ SYNC_OUT G2 G1 EP
Detailed Description
Operating Modes
The MAX9759 filterless, Class D audio power amplifier features several improvements to switch-mode amplifier technology. The MAX9759 offers Class AB performance with Class D efficiency, while occupying minimal board space. A unique modulation scheme, synchronizable switching frequency, and SSM mode create a compact, flexible, low-noise, efficient audio power amplifier. The differential input architecture reduces common-mode noise pickup, and can be used without input-coupling capacitors. The device can also be configured as a single-ended input amplifier. Comparators monitor the MAX9759 inputs and compare the complementary input voltages to the 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, gener10
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. Fixed-Frequency Modulation (FFM) Mode The MAX9759 features two FFM modes. The FFM modes are selected by setting SYNC = GND for a 1.1MHz switching frequency, and SYNC = FLOAT for a 1.5MHz switching frequency. In FFM mode, the frequency spectrum of the class D output consists of the fundamental switching frequency and its associated harmonics (see the Wideband FFT graph in the Typical Operating Characteristics). The MAX9759 allows the switching frequency to be changed, should the frequency of one or more of the harmonics fall in a sensitive band. This can be done at any time and does not affect audio reproduction.
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3.2W, High Efficiency, Low-EMI, Filterless, Class D Audio Amplifier MAX9759
tSW
VIN-
VIN+
OUT-
OUT+
tON(MIN)
VOUT+ - VOUT-
Figure 1. MAX9759 Outputs with an Input Signal Applied
Table 1. Operating Modes
SYNC INPUT GND FLOAT VDD Clocked MODE FFM with fS = 1100kHz FFM with fS = 1500kHz SSM with fS = 1200kHz 70kHz FFM with fS = external clock frequency
Spread-Spectrum Modulation (SSM) Mode The MAX9759 features a unique, patented spread-spectrum mode that reduces peak component energy in the wideband spectrum, improving EMI emissions that may be radiated by the speaker and cables by 5dB.
Proprietary techniques ensure that the cycle-to-cycle variation of the switching period does not degrade audio reproduction or efficiency (see the Typical Operating Characteristics). Select SSM mode by setting SYNC = VDD. In SSM mode, the switching frequency varies by 70kHz around the center frequency (1.2MHz). The modulation scheme remains the same, but the period of the sawtooth waveform changes from cycle to cycle (Figure 2). 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 (Figure 3).
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11
3.2W, High-Efficiency, Low-EMI, Filterless, Class D Audio Amplifier MAX9759
tSW tSW tSW tSW
VIN-
VIN+
OUT-
OUT+
tON(MIN)
VOUT+ - VOUT-
Figure 2. MAX9759 Outputs with an Input Signal Applied (SSM Mode)
External Synchronization The SYNC function allows the MAX9759 to allocate spectral components of the switching harmonics to insensitive frequency bands and facilitates synchronization to a system clock (allowing for a fully synchronous system). Applying an external TTL clock of 1000kHz to 1600kHz to SYNC synchronizes the switching frequency of the MAX9759. The period of the SYNC clock can be randomized, enabling the MAX9759 to be synchronized to another MAX9759 operating in SSM mode. Cascading Amplifiers The SYNC_OUT function of the MAX9759 allows for multiple Maxim class D amplifiers to be cascaded and frequency locked. Synchronizing multiple class D amplifiers ensures that no beat frequencies within the
12
audio spectrum occur on the power-supply rails. Any intermodulation distortion due to the interference of several modulation frequencies is minimized as a result. Leave the SYNC_OUT pin of the MAX9759 floating if the SYNC_OUT function is not applicable.
Filterless Modulation/Common-Mode Idle
The MAX9759 uses Maxim's unique, patented modulation scheme that eliminates the LC filter required by traditional class D amplifiers, improving efficiency, reducing component count, and 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. When no signal is pre-
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3.2W, High Efficiency, Low-EMI, Filterless, Class D Audio Amplifier MAX9759
VIN = 0V
50 45 AMPLITUDE (dBV/m) 40 35 30 25 20 15 30 60 80 100 120 140 160 180 200 220 240 260 280 300 FREQUENCY (MHz) FCC LIMIT
OUTMAX9759 OUTPUT SPECTRUM
OUT+
VOUT+ - VOUT- = 0V
Figure 3. MAX9759 EMI Spectrum
Figure 4. MAX9759 Outputs with No Input Signal
sent at the input of the MAX9759, the outputs switch as shown in Figure 4. Because the MAX9759 drives the speaker differentially, the two outputs cancel each other, resulting in no net Idle ModeTM voltage across the speaker and minimal power consumption.
EFFICIENCY vs. OUTPUT POWER
100 90 80 EFFICIENCY (%) 70 60 50 40 30 20 10 0 0 0.2 0.4 0.6 0.8 1.0 1.2 OUTPUT POWER (W) VDD = 5V f = 1kHz RL = 8 CLASS AB MAX9759
Efficiency
Efficiency of a class D amplifier is mostly associated with the region of operation of the output stage transistors. In a class D amplifier, the output transistors act as current-steering switches and consume negligible additional power. Any power loss associated with the class D output stage is mostly due to the I x R loss of the MOSFET on-resistance and quiescent current overhead. The theoretical best efficiency of a linear amplifier is 78%; however, that efficiency is only exhibited at peak output powers. Under normal operating levels (i.e., typical music reproduction levels), efficiency of a linear amplifier can fall below 30%. The MAX9759 class D amplifier still exhibits >90% efficiencies under the same conditions (Figure 5).
Figure 5. MAX9759 Efficiency vs. Output Power
Gain Selection
The MAX9759 features an internally set, logic-selectable gain. The G1 and G2 logic inputs set the gain of the MAX9759 speaker amplifier (Table 2).
Table 2. Gain Selection
G2 0 0 1 1 G1 0 1 0 1 GAIN (dB) +24 +18 +12 +6
Shutdown
The MAX9759 features a shutdown mode that reduces power consumption and extends battery life. Driving SHDN low places the MAX9759 in a low-power (0.1A) shutdown mode. Drive SHDN high for normal operation.
Idle Mode is a trademark of Maxim Integrated Products, Inc.
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13
3.2W, High-Efficiency, Low-EMI, Filterless, Class D Audio Amplifier MAX9759
Mute
The MAX9759 features a mute function that disables the H-bridge outputs of the switching amplifier. The mute function only affects the power amplifiers of the MAX9759; it does not shut down the device. Driving MUTE low places the MAX9759 in a disabled output mode. Drive MUTE high for normal operation.
1F SINGLE-ENDED AUDIO INPUT IN+
MAX9759
IN1F
Click-and-Pop Suppression
The MAX9759 features comprehensive click-and-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. For 40ms following startup, a soft-start function gradually unmutes the input amplifiers. For improved click-and-pop performance, sequence the digital inputs of the SHDN and MUTE pins of the MAX9759 during power-up and power-down of the device such that transients are eliminated from each power cycle. Apply power to the MAX9759 with both SHDN and MUTE held low. Release SHDN before MUTE such that minimal transients occur during startup of the device. The mute function allows the MAX9759 to be powered up with the H-bridge outputs of the switching amplifier disabled. For power-down, sequence the power cycle such that the amplifier is muted first and subsequently shut down before power is disconnected from the IC. This power cycle eliminates any audible transients on power-up and power-down of the MAX9759.
Figure 6. Single-Ended Input
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 to 100H range.
Power-Conversion Efficiency
Unlike a class AB amplifier, the output offset voltage of a class D amplifier does not noticeably increase quiescent current draw when a load is applied. This is due to the power conversion of the class D amplifier. For example, an 8mV DC offset across an 8 load results in 1mA extra current consumption in a class AB device. In the class D case, an 8mV offset into an 8 load equates to an additional power drain of 8W. Due to the high efficiency of the class D amplifier, this represents an additional quiescent current draw of 8W/(VDD/100), which is on the order of a few microamps.
Input Amplifier
Differential Input The MAX9759 features a differential input structure, making it compatible with many CODECs, and offers improved noise immunity over a single-ended input amplifier. High-frequency signals can be picked up by the amplifier's input traces and can appear at the amplifier's inputs as common-mode noise. A differential input amplifier amplifies the difference of the two inputs; any signal common to both inputs is cancelled. Single-Ended Input The MAX9759 can be configured as a single-ended input amplifier by capacitively coupling one input to GND while simultaneously driving the other input (Figure 6). DC-Coupled Input The input amplifier can accept DC-coupled inputs that are biased within the amplifier's common-mode range (see the Typical Operating Characteristics). DC coupling eliminates the input-coupling capacitors, reducing component count to potentially one external component (see the System Diagram). However, the low-frequency rejection of the capacitors is lost, allowing low-frequency signals to feedthrough to the load.
Applications Information
Filterless Operation
Traditional class D amplifiers require an output filter to recover the audio signal from the amplifier's 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 peak-to-peak) and causes large ripple currents. Any parasitic resistance in the filter components results in a loss of power, lowering the efficiency. The MAX9759 does not require an output filter for the short speaker cable. The device relies 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 MAX9759 output is well beyond the bandwidth of most speakers, voice coil movement due to the switching frequency is very small.
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3.2W, High-Efficiency, Low-EMI, Filterless, Class D Audio Amplifier MAX9759
VDD
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
100
VDD PVDD
U1
10
VDD = 5.0V f = 1kHz RL = 8 SLAVE DEVICE
MAX9759 SYNC
THD+N (%)
RIGHT-CHANNEL DIFFERENTIAL AUDIO INPUT IN+ OUT+
1
IN-
OUTSYNC_OUT
0.1
0.01 0.001 0
VDD U2 PVDD
0.5
1.0 OUTPUT POWER (W)
1.5
2.0
MAX9759 SYNC
LEFT-CHANNEL DIFFERENTIAL AUDIO INPUT IN+ OUT+
Figure 8. Total Harmonic Distortion Plus Noise vs. Output Voltage
INSYNC_OUT
CROSSTALK vs. FREQUENCY
-30 -50 CROSSTALK (dB) -70 MASTER TO SLAVE -90 -110 -130 SLAVE TO MASTER VDD = 5V RL = 8 f = 1kHz
VDD
PVDD
MAX9759 SYNC
IN+ DIFFERENTIAL AUDIO INPUT INSYNC_OUT OUT+
-150 10 100 1k FREQUENCY (Hz) 10k 100k
Figure 9. Crosstalk vs. Frequency Figure 7. Master-Slave Configuration
Component Selection
Input Filter An input capacitor, CIN, in conjunction with the input impedance of the MAX9759 forms a highpass filter that removes the DC bias from an incoming signal. The ACcoupling capacitor allows the amplifier to 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/(2RINCIN) Choose CIN such that f-3dB is well below the lowest frequency of interest. Setting f-3dB too high affects the low-frequency response of the amplifier. 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.
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15
3.2W, High-Efficiency, Low-EMI, Filterless, Class D Audio Amplifier
1F 22k IN-
CW 50k 1F 22k
MAX9759
IN+
Use wide, low-resistance output traces. As load impedance decreases, the current drawn from the device outputs increase. At higher current, the resistance of the output traces decrease the power delivered to the load. Wide output, supply, and GND traces also improve the power dissipation of the device. The MAX9759 thin QFN package features an exposed thermal pad on its underside. This pad lowers the package's thermal resistance by providing a direct heat conduction path. Due to the high efficiency of the MAX9759's Class D Amplifier, additional heatsinking is not required. If additional heatsinking is required, connect the exposed paddle to GND.
MAX9759
MAX9759
Stereo Configuration
Figure 10. Single-Ended Drive of MAX9759 Plus Volume Control
Output Filter The MAX9759 does not require an output filter for the short speaker cable. The device passes FCC emissions standards with 7.6cm of unshielded speaker cables. However, output filtering can be used if a design is failing radiated emissions due to board layout, cable length, or the circuit's close proximity to EMI-sensitive devices. Use an LC filter when radiated emissions are a concern, or when long leads are used to connect the amplifier to the speaker.
Supply Bypassing, Layout, and Grounding
Proper power-supply bypassing ensures low-distortion operation. For optimum performance, bypass VDD to GND and PVDD to PGND with separate 0.1F capacitors as close to each pin as possible. A low-impedance, high-current, power-supply connection to PVDD is assumed. Additional bulk capacitance should be added as required depending on the application and power-supply characteristics. GND and PGND should be star-connected to system ground.
Two MAX9759s can be configured as a stereo amplifier (Figure 7). Device U1 is the master amplifier; its oscillator output, SYNC_OUT, drives the SYNC input of the slave device (U2), synchronizing the switching frequencies of the two devices. Synchronizing two MAX9759s ensures that no beat frequencies within the audio spectrum occur on the power-supply rails. This stereo configuration works when the master device is in either FFM or SSM mode. There is excellent THD+N performance and minimal crosstalk between devices due to the SYNC and SYNC_OUT connection (Figures 8, 9). Multiple MAX9759s can be cascaded and frequency locked in a similar fashion (Figure 7). Repeat the stereo configuration outlined in Figure 7 for multiple cascading amplifier applications.
Volume Control
If volume control is required, connect a potentiometer between the differential inputs of the MAX9759, as seen in Figure 10. In this configuration, each input "sees" identical RC paths when the device is powered up. The variable resistive element appears between the two inputs, meaning the setting affects both inputs the same way. This configuration significantly improves transient performance on power-up or release from SHDN.
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3.2W, High-Efficiency, Low-EMI, Filterless, Class D Audio Amplifier
System Diagram
AVDD 1F OUT-R IN+ IN2.1 AUDIO CODEC 1F VDD G2 MUTE SHDN G1 PGND GND PVDD VDD 1F VDD
MAX9759
MAX9759
OUT+ OUTVDD SYNC
AVSS
OUT-R 8 SPEAKER
EAPD CENTER OUT OUT-L AVSS
SYNC_OUT
1F IN+ IN1F VDD G2 MUTE SHDN G1 PGND GND SYNC PV DD VDD
VDD
1F
MAX9759
OUT+ OUT-
AVSS
CENTER OUT 4 SPEAKER
SYNC_OUT
1F IN+ IN1F VDD G2 MUTE SHDN G1 PGND GND SYNC PV DD VDD
VDD
1F
MAX9759
OUT+ OUT-
AVSS
OUT-L 8 SPEAKER
SYNC_OUT
NOTE: SYSTEM DIAGRAM DEPICTS MAX9759 IN SSM MODE WITH fS = 1200 70kHz AND +12dB OF GAIN.
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17
3.2W, High-Efficiency, Low-EMI, Filterless, Class D Audio Amplifier MAX9759
Pin Configurations
TOP VIEW
PVDD OUT+ PVDD OUTOUT+ PVDD SYNC_OUT 13 PGND 14 G2 15 G1 16 1 VDD 2 IN+ 3 IN4 GND 8 7 MUTE SYNC PGND 6 5 PGND G2 SHDN G1 VDD IN+ 6 7 8 TSSOP 11 SHDN 10 GND 9 IN5 12 PGND 4 13 SYNC SYNC_OUT 1 2 3 16 OUT15 PVDD
12
11
10
9
MAX9759
14 MUTE
MAX9759
THIN QFN
Chip Information
TRANSISTOR COUNT: 4219 PROCESS: BiCMOS
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3.2W, High-Efficiency, Low-EMI, Filterless, Class D Audio Amplifier
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.)
24L QFN THIN.EPS
MAX9759
PACKAGE OUTLINE, 12, 16, 20, 24, 28L THIN QFN, 4x4x0.8mm
21-0139
D
1
2
PACKAGE OUTLINE, 12, 16, 20, 24, 28L THIN QFN, 4x4x0.8mm
21-0139
D
2
2
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3.2W, High-Efficiency, Low-EMI, Filterless, Class D Audio Amplifier MAX9759
Package Information (continued)
(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.)
TSSOP4.40mm.EPS
MAX9759
PACKAGE OUTLINE, TSSOP 4.40mm BODY
21-0066
G
1
1
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.
20 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2005 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products, Inc.

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