19-3691; Rev 0; 5/05 3.2W, High-Efficiency, Low-EMI, Filterless, Class D Audio Amplifier 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 4Ω 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 -40°C to +85°C temperature range. Features ♦ 3.2W into 4Ω 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 (10µA) ♦ 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 Ordering Information TEMP RANGE PIN-PACKAGE MAX9759ETE+ PART -40°C to +85°C 16 TQFN-EP* MAX9759EUE+ -40°C to +85°C 16 TSSOP +Denotes lead-free package. *EP = Exposed paddle. Simplified Block Diagram Applications VDD Cell Phones/PDAs Notebook PCs Portable DVD Players DIFFERENTIAL AUDIO INPUT MODULATOR AND H-BRIDGE MONO SPEAKER OUTPUT Flat-Panel PC Monitors LCD TVs LCD Projectors SYNC INPUT OSCILLATOR SYNC OUTPUT MAX9759 GAIN CONTROL G1 G2 SHDN CONTROL SHDN MUTE CONTROL MUTE Pin Configurations appear at end of data sheet. ________________________________________________________________ Maxim Integrated Products 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. 1 MAX9759 General Description MAX9759 3.2W, High-Efficiency, Low-EMI, Filterless, Class D Audio Amplifier 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 = +70°C) 16-Pin TQFN (derate 16.9mW/°C above +70°C) .....1349.1mW 16-Pin TSSOP (derate 9.4mW/°C above +70°C) .......754.7mW Junction Temperature ......................................................+150°C Operating Temperature Range ...........................-40°C to +85°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C 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 = +25°C.) (Notes 1, 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS GENERAL Supply Voltage Range VDD Inferred from PSRR test Quiescent Current IDD No load 8.4 IMUTE V MUTE = 0V IDD(SHDN) V SHDN = 0V Mute Current Shutdown Current Shutdown to Full Operation tSON Mute to Full Operation tMUTE Common-Mode Rejection Ratio CMRR Input DC Bias Voltage Input Resistance f = 1kHz, input referred, VIN = 200mVP-P VCM RIN Output Offset Voltage AV VOS 2 PSRR V 12 mA 5.5 8 mA 0.1 10 ms 40 ms 67 dB 1.7 Gain = +24dB 14 20 26 Gain = +18dB 25 36 47 Gain = +12dB 40 60 80 60 90 120 G1 = 0, G2 = 0 +22 +24 +26 G1 = 1, G2 = 0 +16 +18 +20 G1 = 0, G2 = 1 +10 +12 +14 G1 = 1, G2 = 1 +4 +6 +8 ±10 ±50 TA = +25°C 200mVP-P ripple 62 µA 40 1.5 VDD = 4.5V to 5.5V Power-Supply Rejection Ratio (Note 3) 5.5 1.3 Gain = +6dB Voltage Gain 3.0 V kΩ dB mV 90 fRIPPLE = 217Hz 79 fRIPPLE = 1kHz 81 fRIPPLE = 20kHz 70 _______________________________________________________________________________________ dB 3.2W, High Efficiency, Low-EMI, Filterless, Class D Audio Amplifier (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 = +25°C.) (Notes 1, 2) PARAMETER SYMBOL CONDITIONS THD+N = 1% Output Power POUT THD+N = 10% Total Harmonic Distortion Plus Noise Signal-to-Noise Ratio Oscillator Frequency THD+N SNR fOSC fIN = 1kHz, either FFM or SSM, POUT = 1W POUT = 1W, RL = 8Ω MIN 3.4 RL = 4Ω 2.6 RL = 8Ω 1.4 RL = 3Ω 4.3 RL = 4Ω 3.2 RL = 8Ω 1.8 RL = 3Ω 0.08 RL = 4Ω 0.05 RL = 8Ω 0.02 BW = 22Hz to 22kHz A-weighted FFM Click-and-Pop Level 89 FFM 96 η Efficiency % SSM dB 92 1000 1100 1200 SYNC = FLOAT (FFM mode) 1102 1500 1837 Peak voltage, A-weighted, 32 samples per second (Notes 3, 4) UNITS W SYNC = GND (FFM mode) kHz 1200 ±70 TTL-compatible clock input KCP MAX 93 SSM SYNC = VDD (SSM mode) SYNC Frequency Lock Range TYP RL = 3Ω 1000 1600 Into shutdown -50 Out of shutdown -57 kHz dB POUT = 1W, fIN = 1kHz, RL = 8Ω in series with 68µH 92 % DIGITAL INPUTS (SHDN, MUTE, G1, G2, SYNC) SYNC, G1, G2 Input Voltage High VINH SYNC, G1, G2 Input Voltage Low VINL SHDN, MUTE Voltage High VINH SHDN, MUTE Voltage Low VINL VDD x 0.9 V VDD x 0.1 2 V 0.8 SYNC Input Resistance 200 SYNC Input Current SHDN, MUTE, G1, G2 Input Current SYNC Capacitance V V kΩ ±35 µA ±1 µA 10 pF DIGITAL OUTPUTS (SYNC_OUT) Output Voltage High VOH IOH = 3mA Output Voltage Low VOL IOL = 3mA SYNC_OUT Capacitive Drive TTL-compatible clock output 2.4 V 0.4 100 V pF _______________________________________________________________________________________ 3 MAX9759 ELECTRICAL CHARACTERISTICS (VDD = 5.0V) (continued) MAX9759 3.2W, High-Efficiency, Low-EMI, Filterless, Class D Audio Amplifier 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 = +25°C.) (Notes 1, 2) PARAMETER Quiescent Current Mute Current SYMBOL CONDITIONS MIN IDD TYP MAX UNITS 6 mA A IMUTE V MUTE = 0V 5 Shutdown Current ISHDN V SHDN = 0V 0.1 µA Common-Mode Rejection Ratio CMRR f = 1kHz, input referred 67 dB dB fRIPPLE = 217Hz 72 79 dB VDD = 3.0V to 5.5V Power-Supply Rejection Ratio PSRR 200mVP-P ripple THD+N = 1% Output Power POUT THD+N = 10% Total Harmonic Distortion Plus Noise Signal-to-Noise Ratio THD+N SNR f = 1kHz, either FFM or SSM, POUT = 500mW POUT = 500mW, RL = 8Ω 50 fRIPPLE = 1kHz 81 fRIPPLE = 20kHz 70 RL = 3Ω 1.5 RL = 4Ω 1.1 RL = 8Ω 0.65 RL = 3Ω 1.8 RL = 4Ω 1.3 RL = 8Ω 0.78 RL = 3Ω 0.06 RL = 4Ω 0.04 RL = 8Ω 0.02 BW = 22Hz to 22kHz A-weighted FFM W % 93 SSM 89 FFM 96 SSM 92 dB Note 1: All devices are 100% production tested at +25°C. All temperature limits are guaranteed by design. Note 2: Testing performed with a resistive load in series with an inductor to simulate an actual speaker load. For RL = 4Ω, L = 33µH. For RL = 8Ω, L = 68µH. Note 3: Inputs AC-coupled to GND. Note 4: Testing performed with 8Ω resistive load in series with a 68µH inductive load across BTL outputs. Mode transitions are controlled by the SHDN pin. 4 _______________________________________________________________________________________ 3.2W, High-Efficiency, Low-EMI, Filterless, Class D Audio Amplifier (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 = +25°C.) (See Typical Operating Circuit) TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY VDD = 5V RL = 3Ω VDD = 3.3V RL = 3Ω 0.1 POUT = 2.6W 0.01 1 POUT = 500mW THD+N (%) THD+N (%) 0.1 0.01 10 100 1k 10k POUT = 2.2W 0.01 0.001 10 100k 0.1 POUT = 1.3W 0.001 0.001 POUT = 1W 100 1k 100k 10k 10 100 1k 10k 100k FREQUENCY (Hz) FREQUENCY (Hz) FREQUENCY (Hz) TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY VDD = 5V RL = 8Ω VDD = 3.3V RL = 8Ω 1 POUT = 500mW 0.1 0.01 THD+N (%) 1 THD+N (%) 1 10 POUT = 600mW 0.1 POUT = 500mW 0.001 0.001 100 1k 10k POUT = 300mW POUT = 1.2W 0.001 10 0.1 0.01 0.01 POUT = 700mW 100k MAX9759 toc06 VDD = 3.3V RL = 4Ω MAX9759 toc05 10 MAX9759 toc04 10 10 100 1k 10k 10 100k 100 1k 10k 100k FREQUENCY (Hz) FREQUENCY (Hz) TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER 100 MAX9759 toc07 VDD = 5V RL = 8Ω POUT = 1.2W VDD = 5V RL = 3Ω 10 0.1 THD+N (%) 1 SSM 1 100 fIN = 200Hz, 1kHz 0.1 VDD = 3.3V RL = 3Ω 10 THD+N (%) 10 MAX9759 toc09 FREQUENCY (Hz) MAX9759 toc08 THD+N (%) POUT = 1W THD+N (%) VDD = 5V RL = 4Ω 1 1 THD+N (%) 10 MAX9759 toc02 10 MAX9759 toc01 10 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY MAX9759 toc03 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY 1 fIN = 200Hz, 1kHz 0.1 fIN = 10kHz 0.01 fIN = 10kHz 0.01 FFM 0.001 0.001 0.001 10 100 1k FREQUENCY (Hz) 10k 100k 0.01 0 1 2 3 OUTPUT POWER (W) 4 0 0.5 1.0 1.5 2.0 OUTPUT POWER (W) _______________________________________________________________________________________ 5 MAX9759 Typical Operating Characteristics 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 = +25°C.) (See Typical Operating Circuit) TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER 1 fIN = 200Hz, 1kHz 0.1 1 fIN = 200Hz, 1kHz 0.1 fIN = 10kHz 0 2 1 3 1.0 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER 0.5 0 1.0 1.5 2.0 EFFICIENCY vs. OUTPUT POWER MAX9759 toc14 100 90 80 EFFICIENCY (%) fIN = 200Hz, 1kHz 0.1 VDD = 5V fIN = 1kHz RL = 8Ω 10 THD+N (%) 1 fIN = 10kHz OUTPUT POWER (W) 100 MAX9759 toc13 10 0.1 1.5 OUTPUT POWER (W) VDD = 3.3V RL = 8Ω fIN = 200Hz, 1kHz 0.001 0.5 0 OUTPUT POWER (W) 100 1 0.01 0.001 0.001 THD+N (%) 10 fIN = 10kHz 0.01 0.01 VDD = 5V RL = 8Ω THD+N (%) 10 MAX9759 toc12 VDD = 3.3V RL = 4Ω THD+N (%) 10 100 MAX9759 toc11 VDD = 5V RL = 4Ω THD+N (%) 100 MAX9759 toc10 100 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER 1 f = 1180kHz, FFM 0.1 MAX9759 toc15 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER RL = 8Ω 70 RL = 4Ω RL = 3Ω 60 50 40 30 0.01 20 0.01 fIN = 10kHz f = 1400kHz, FFM 0.001 0.2 0.4 0.6 0.8 0 0 0.5 1.0 1.5 2 3 OUTPUT POWER (W) EFFICIENCY vs. OUTPUT POWER EFFICIENCY vs. SUPPLY VOLTAGE OUTPUT POWER vs. SUPPLY VOLTAGE 80 RL = 3Ω 50 40 30 RL = 8Ω RL = 4Ω 70 60 50 40 VDD = 3.3V fIN = 1kHz 0.5 1.0 OUTPUT POWER (W) 1.5 2.0 MAX9759 toc18 THD+N = 10% 3 2 1 fIN = 1kHz THD+N = 1% 30 0 4 5 THD+N = 1% 20 10 RL = 3Ω fIN = 1kHz 5 OUTPUT POWER (W) RL = 4Ω 60 EFFICIENCY (%) RL = 8Ω 90 4 6 MAX9759 toc17 100 MAX9759 toc16 80 6 1 OUTPUT POWER (W) 90 0 0 2.0 OUTPUT POWER (W) 100 70 VDD = 5V fIN = 1kHz 10 0.001 0 EFFICIENCY (%) MAX9759 3.2W, High-Efficiency, Low-EMI, Filterless, Class D Audio Amplifier 0 3.0 3.5 4.0 5.0 4.5 SUPPLY VOLTAGE (V) 5.5 3.0 3.5 4.0 4.5 5.0 SUPPLY VOLTAGE (V) _______________________________________________________________________________________ 5.5 3.2W, High Efficiency, Low-EMI, Filterless, Class D Audio Amplifier (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 = +25°C.) (See Typical Operating Circuit) OUTPUT POWER vs. SUPPLY VOLTAGE 2.0 OUTPUT POWER (W) OUTPUT POWER (W) RL = 8Ω fIN = 1kHz 3.0 THD+N = 10% 2.5 2.0 1.5 THD+N = 1% MAX9759 toc20 RL = 4Ω fIN = 1kHz 3.5 2.5 MAX9759 toc19 4.0 OUTPUT POWER vs. SUPPLY VOLTAGE THD+N = 10% 1.5 1.0 THD+N = 1% 1.0 0.5 0.5 0 0 4.0 4.5 5.0 3.0 4.0 5.0 4.5 SUPPLY VOLTAGE (V) OUTPUT POWER vs. LOAD RESISTANCE OUTPUT POWER vs. LOAD RESISTANCE 4.0 3.5 3.0 2.5 2.0 10% THD+N 1.5 5.5 2.0 VDD = 3.3V fIN = 1kHz 1.8 1.6 OUTPUT POWER (W) VDD = 5V fIN = 1kHz 4.5 1.4 1.2 1.0 10% THD+N 0.8 0.6 0.4 1.0 0.5 1% THD+N 0.2 1% THD+N 0 0 1 1 100 10 100 10 LOAD RESISTANCE (Ω) LOAD RESISTANCE (Ω) TOTAL HARMONIC DISTORTION PLUS NOISE vs. COMMON-MODE VOLTAGE TOTAL HARMONIC DISTORTION PLUS NOISE vs. COMMON-MODE VOLTAGE 0.1 0.01 VDD = 3.3V 5V RL = 8Ω fIN = 1kHz POUT = 300mW DIFF INPUT 10 THD+N (%) 1 MAX9759 toc24 VDD = 5V RL = 8Ω fIN = 1kHz POUT = 300mW DIFF INPUT 10 100 MAX9759 toc23 100 THD+N (%) 3.5 SUPPLY VOLTAGE (V) 5.0 OUTPUT POWER (W) 5.5 MAX9759 toc22 3.5 MAX9759 toc21 3.0 1 0.1 0.01 0.001 0 1 2 3 COMMON-MODE VOLTAGE (V) 4 0.001 0 1 2 3 4 COMMON-MODE VOLTAGE (V) _______________________________________________________________________________________ 7 MAX9759 Typical Operating Characteristics (continued) 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 = +25°C.) (See Typical Operating Circuit) -40 -40 -50 -60 -50 -60 -70 -70 -80 -80 -90 -90 -100 100 1k 10k -140 10 100 1k 5k 0 100k 10k 10k OUTPUT FREQUENCY SPECTRUM WIDEBAND OUTPUT SPECTRUM (FFM MODE) WIDEBAND OUTPUT SPECTRUM (SSM MODE) -100 20 -120 -140 5k 10k 15k 20k RBW = 10kHz 30 10 0 -10 -20 -30 20 10 0 -10 -20 -30 -40 -50 -50 -60 -60 1M 10M 100M 1000M 1M FREQUENCY (Hz) FREQUENCY (Hz) 10M 100M FREQUENCY (Hz) MUTE RESPONSE SHUTDOWN RESPONSE MAX9759 toc32 MAX9759 toc31 5V SHDN 5V MUTE 0V 0V MAX9759 OUTPUT 500mV/div f = 1kHz RL = 8Ω MAX9759 OUTPUT 500mV/div f = 1kHz RL = 8Ω 20ms/div 20k 40 OUTPUT AMPLITUDE (dBV) OUTPUT AMPLITUDE (dBV) -80 RBW = 10kHz 30 MAX9759 toc29 MAX9759 toc28 40 -40 8 15k FREQUENCY (Hz) -60 0 -100 FREQUENCY (Hz) SSM MODE VOUT = -60dBV fIN = 1kHz RL = 8Ω UNWEIGHTED -40 -80 FREQUENCY (Hz) 0 -20 100k -60 -120 -100 10 -40 MAX9759 toc30 -30 FFM MODE VOUT = -60dBV fIN = 1kHz RL = 8Ω UNWEIGHTED -20 OUTPUT MAGNITUDE (dBV) -20 -30 PSRR (dB) CMRR (dB) -20 OUTPUT REFERRED INPUTS AC GROUNDED -10 0 MAX9759 toc26 INPUT REFERRED VIN = 200mVP-P -10 OUTPUT FREQUENCY SPECTRUM 0 MAX9759 toc25 0 POWER-SUPPLY REJECTION RATIO vs. FREQUENCY MAX9759 toc27 COMMON-MODE REJECTION RATIO vs. FREQUENCY OUTPUT MAGNITUDE (dBV) MAX9759 3.2W, High-Efficiency, Low-EMI, Filterless, Class D Audio Amplifier 20ms/div _______________________________________________________________________________________ 1000M 3.2W, High-Efficiency, Low-EMI, Filterless, Class D Audio Amplifier (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 = +25°C.) (See Typical Operating Circuit) SHUTDOWN SUPPLY CURRENT vs. SUPPLY VOLTAGE SUPPLY CURRENT (mA) TA = +25°C 7.5 7.0 TA = -40°C 6.5 6.0 FFM 0.18 TA = +85°C 0.16 0.14 0.12 TA = +25°C 0.10 0.08 0.06 5.5 0.04 5.0 0.02 TA = -40°C 3.0 3.5 4.0 4.5 5.0 50 RL = 3Ω AT 10% THD+N 40 RL = 4Ω AT 10% THD+N 30 20 RL = 8Ω AT 10% THD+N MAX9759EVKIT FREE AIR TA = +25°C fIN = 1kHz SINE WAVE 10 0 4.5 60 MAX9759 toc35 8.0 MAX9759 toc34 TA = +85°C SUPPLY CURRENT (µA) FFM 8.5 0.20 MAX9759 toc33 9.0 PACKAGE TEMPERATURE vs. TIME PACKAGE TEMPERATURE (°C) SUPPLY CURRENT vs. SUPPLY VOLTAGE 0 4.7 4.5 5.5 4.9 5.1 5.3 5.5 0 50 100 SUPPLY VOLTAGE (V) SUPPLY VOLTAGE (V) 150 200 250 300 TIME (s) Typical Operating Circuit/Functional Diagram VDD VDD GND 8 (14) 10µF* 5 (11) MUTE SHDN 1 (7) 9, 12 (2, 15) VDD PVDD UVLO/POWER MANAGEMENT 16 (6) G1 G2 1µF CLICK-AND-POP SUPPRESSION PVDD CONTROL 15 (5) RF 1µF 2 (8) IN+ RIN 1µF 3 (9) IN- RIN 11 OUT+ (1) CLASS D MODULATOR PVDD OUT- 10 (16) BIAS RF 7 (13) SYNC OSCILLATOR MAX9759 13 SYNC_OUT (3) PGND ( ) TSSOP 6, 14 (4, 12) GND 4 (10) NOTE: TYPICAL OPERATING CIRCUIT DEPICTS MAX9759 IN FFM MODE WITH fS = 1400kHz and +18dB OF GAIN. *BULK CAPACITANCE, IF NEEDED. _______________________________________________________________________________________ 9 MAX9759 Typical Operating Characteristics (continued) 3.2W, High-Efficiency, Low-EMI, Filterless, Class D Audio Amplifier MAX9759 Pin Description PIN NAME FUNCTION TQFN TSSOP 1 7 VDD 2 8 IN+ Noninverting Audio Input 3 9 IN- Inverting Audio Input 4 10 GND Analog Ground 5 11 SHDN Active-Low Shutdown Input. Drive SHDN low to shut down the MAX9759. Connect to VDD for normal operation. 6, 14 4, 12 PGND Power Ground Analog Power Supply. Bypass to GND with a 1µF ceramic capacitor. 7 13 SYNC 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. 8 14 MUTE Active-Low Mute Function. Drive MUTE low to disable the H-bridge outputs. Connect to VDD for normal operation. 9, 12 2, 15 PVDD H-Bridge Power Supply. Bypass to PGND with a 10µF ceramic capacitor. 10 16 OUT- Negative Speaker Output 11 1 OUT+ Positive Speaker Output 13 3 SYNC_OUT 15 5 G2 16 6 G1 Gain Control 1 (See the Gain Selection Section) EP EP EP Exposed Paddle. Can be left floating or tied to GND. 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) 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. ______________________________________________________________________________________ 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). ______________________________________________________________________________________ 11 MAX9759 3.2W, High-Efficiency, Low-EMI, Filterless, Class D Audio Amplifier 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- ______________________________________________________________________________________ 3.2W, High Efficiency, Low-EMI, Filterless, Class D Audio Amplifier MAX9759 VIN = 0V 50 FCC LIMIT AMPLITUDE (dBµV/m) 45 40 35 OUT- 30 MAX9759 OUTPUT SPECTRUM 25 20 OUT+ 15 30 60 80 100 120 140 160 180 200 220 240 260 280 300 FREQUENCY (MHz) 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 Mode™ voltage across the speaker and minimal power consumption. EFFICIENCY vs. OUTPUT POWER 100 90 80 70 EFFICIENCY (%) 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). MAX9759 60 50 CLASS AB 40 30 20 VDD = 5V f = 1kHz RL = 8Ω 10 0 0 0.2 0.4 0.6 0.8 1.0 1.2 OUTPUT POWER (W) 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). 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 (0.1µA) shutdown mode. Drive SHDN high for normal operation. Table 2. Gain Selection G2 G1 GAIN (dB) 0 0 +24 0 1 +18 1 0 +12 1 1 +6 Idle Mode is a trademark of Maxim Integrated Products, Inc. ______________________________________________________________________________________ 13 MAX9759 3.2W, High-Efficiency, Low-EMI, Filterless, Class D Audio Amplifier 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. 1µF SINGLE-ENDED AUDIO INPUT IN+ MAX9759 IN1µF 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. 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. 14 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 > 10µH to 100µH 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 8Ω load results in 1mA extra current consumption in a class AB device. In the class D case, an 8mV offset into an 8Ω load equates to an additional power drain of 8µW. Due to the high efficiency of the class D amplifier, this represents an additional quiescent current draw of 8µW/(VDD/100η), 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. ______________________________________________________________________________________ 3.2W, High-Efficiency, Low-EMI, Filterless, Class D Audio Amplifier MAX9759 VDD TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER 100 VDD U1 PVDD VDD = 5.0V f = 1kHz RL = 8Ω SLAVE DEVICE 10 RIGHT-CHANNEL DIFFERENTIAL AUDIO INPUT OUT+ IN- OUT- THD+N (%) MAX9759 SYNC IN+ 1 0.1 SYNC_OUT 0.01 0.001 0 VDD U2 MAX9759 SYNC LEFT-CHANNEL DIFFERENTIAL AUDIO INPUT IN+ 0.5 1.0 1.5 2.0 OUTPUT POWER (W) PVDD Figure 8. Total Harmonic Distortion Plus Noise vs. Output Voltage OUT+ IN- CROSSTALK vs. FREQUENCY SYNC_OUT VDD = 5V RL = 8Ω f = 1kHz -30 VDD PVDD MAX9759 SYNC IN+ OUT+ DIFFERENTIAL AUDIO INPUT CROSSTALK (dB) -50 -70 MASTER TO SLAVE -90 -110 SLAVE TO MASTER -130 INSYNC_OUT -150 10 1k 100 10k 100k FREQUENCY (Hz) 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/(2πRINCIN) 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. ______________________________________________________________________________________ 15 1µF 22kΩ CW IN- 50kΩ 1µF 22kΩ 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. 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 0.1µF 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. 16 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. ______________________________________________________________________________________ MAX9759 MAX9759 3.2W, High-Efficiency, Low-EMI, Filterless, Class D Audio Amplifier 3.2W, High-Efficiency, Low-EMI, Filterless, Class D Audio Amplifier AVDD VDD 1µF OUT-R 2.1 AUDIO CODEC IN+ PVDD IN- VDD 1µF 1µF AVSS MAX9759 VDD G2 MUTE SHDN G1 EAPD CENTER OUT OUT-L OUT-R 8Ω SPEAKER OUTVDD SYNC PGND GND AVSS OUT+ SYNC_OUT VDD 1µF IN+ SYNC PV DD IN- VDD 1µF 1µF AVSS MAX9759 VDD G2 MUTE SHDN G1 OUT+ CENTER OUT 4Ω SPEAKER OUT- SYNC_OUT PGND GND VDD 1µF IN+ SYNC PV DD IN- VDD 1µF 1µF AVSS MAX9759 VDD G2 MUTE SHDN G1 OUT+ OUT-L 8Ω SPEAKER OUT- SYNC_OUT PGND GND NOTE: SYSTEM DIAGRAM DEPICTS MAX9759 IN SSM MODE WITH fS = 1200 ±70kHz AND +12dB OF GAIN. ______________________________________________________________________________________ 17 MAX9759 System Diagram 3.2W, High-Efficiency, Low-EMI, Filterless, Class D Audio Amplifier MAX9759 Pin Configurations PVDD OUT+ OUT- PVDD TOP VIEW 12 11 10 9 SYNC_OUT 13 8 MUTE PGND 14 7 SYNC MAX9759 G2 15 2 3 4 IN- GND VDD 1 IN+ G1 16 6 PGND 5 SHDN OUT+ 1 PVDD 2 16 OUT15 PVDD MAX9759 SYNC_OUT 3 PGND 4 14 MUTE 13 SYNC G2 5 12 PGND G1 6 11 SHDN VDD 7 10 GND IN+ 8 9 IN- THIN QFN TSSOP Chip Information TRANSISTOR COUNT: 4219 PROCESS: BiCMOS 18 ______________________________________________________________________________________ 3.2W, High-Efficiency, Low-EMI, Filterless, Class D Audio Amplifier 24L QFN THIN.EPS 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 ______________________________________________________________________________________ 19 MAX9759 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.) Package Information (continued) TSSOP4.40mm.EPS (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.) 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 © 2005 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products, Inc. MAX9759 MAX9759 3.2W, High-Efficiency, Low-EMI, Filterless, Class D Audio Amplifier