19-3681; Rev 0; 12/05 KIT ATION EVALU E L B AVAILA 3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover 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 4Ω 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 DirectDrive™ 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 16Ω 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 1µA. All amplifiers feature click-and-pop suppression circuitry. Both devices are fully specified over the -40°C to +85°C extended temperature range and are available in the thermally enhanced 36-pin (6mm x 6mm x 0.8mm) thin QFN package. Applications Notebook Audio Solutions Multimedia Monitors 2.1 Speaker Solutions Portable DVD Players Desktop PCs Table-Top LCD TVs Features ♦ Triple Class D Amplifiers Deliver 3 x 2.3W into 4Ω ♦ 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 Ordering Information PART HP AMP PIN-PACKAGE PKG CODE MAX9706ETX+ Yes 36 Thin QFN T3666N-1 MAX9707ETX+ No 36 Thin QFN T3666N-1 +Denotes lead-free package. Note: These devices operate over the -40°C to +85°C temperature range. Functional Diagrams and Pin Configurations appear at end of data sheet. Block Diagram MAX9706 MAX9707 AUDIO IN FULL-RANGE TRANSDUCERS AUDIO IN LOW-FREQUENCY TRANSDUCER FREQUENCY SELECT SHDN HEADPHONE FULL-RANGE TRANSDUCERS LOW-FREQUENCY TRANSDUCER FREQUENCY SELECT SHDN ________________________________________________________________ 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 MAX9706/MAX9707 General Description MAX9706/MAX9707 3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover 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 = +70°C) Single-Layer Board 36-Pin TQFN (derate 26.3mW/°C above +70°C) .......2105mW Multilayer Board 36-Pin TQFN (derate 35.7mW/°C above +70°C) .......2857mW Operating Temperature Range ...........................-40°C to +85°C Storage Temperature Range .............................-65°C to +150°C Junction Temperature ......................................................+150°C Lead Temperature (soldering, 10s) .................................+300°C 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 = 1µF to GND, C1 = 1µF, C2 = 1µF. TA = TMIN to TMAX, unless otherwise noted. Typical values at TA = +25°C.) (Note 1) PARAMETER Speaker Amplifier Supply Voltage Range Headphone Amplifier Supply Voltage Range SYMBOL VDD, PVDD Inferred from PSRR test HPVDD, CPVDD Quiescent Supply Current IDD Shutdown Supply Current ISHDN Input Resistance CONDITIONS Inferred from PSRR test (MAX9706) TYP MAX UNITS 4.5 5.5 V 3.0 5.5 V Speaker mode 25 35 Headphone mode, HPS = VDD (MAX9706) 7 12 0.5 3 µA 25 35 kΩ SHDN = GND RIN Turn-On Time, Shutdown to Full Operation MIN 15 Speaker mode 87 Headphone mode (MAX9706) 87 mA ms SPEAKER AMPLIFIERS (OUTL_, OUTR_, OUTM_) Output Power (Note 2) Total Harmonic Distortion Plus Noise Signal-to-Noise Ratio POUT THD+N SNR RL = 8Ω, THD+N = 1% 1.4 RL = 4Ω, THD+N = 1% 2.3 POUT = 1W, bandwidth = 22Hz to 22kHz (Note 2) RL = 8Ω, POUT = 1W (Note 2) RL = 8Ω 0.06 RL = 4Ω 0.07 % Bandwidth = 22Hz to 22kHz 87 A-weighted 92 VDD = PVDD = 4.5V to 5.5V, TA = +25°C Power-Supply Rejection Ratio 2 PSRR 100mVP-P ripple (Note 3) W 50 dB 71 f = 2kHz, OUTL_, OUTR_ 51 f = 100Hz, OUTM_ 65 _______________________________________________________________________________________ dB 3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover (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 = 1µF to GND, C1 = 1µF, C2 = 1µF. TA = TMIN to TMAX, unless otherwise noted. Typical values at TA = +25°C.) (Note 1) PARAMETER SYMBOL Speaker Path Gain (Note 4) CONDITIONS MIN GAIN2 = 0 GAIN1 = 0 9 GAIN2 = 0 GAIN1 = 1 10.5 GAIN2 = 1 GAIN1 = 0 12 GAIN2 = 1 GAIN1 = 1 13.5 Channel-to-Channel Gain Tracking Crosstalk CL η Efficiency Class D Center Frequency MAX fOSC MGAIN = GND -4.5 MGAIN = float -6 MGAIN = VDD -7.5 % dB Right to left, left to right, fIN = 10kHz, POUT = 1W 70 dB No sustained oscillations 200 pF RL = 8Ω, POUT = 3 x 1W, f = 800Hz 90 RL = 4Ω, POUT = 3 x 1W, f = 800Hz 88 % FFM, SYNC_IN = GND 955 1100 1270 FFM, SYNC_IN = float 1140 1340 1540 kHz 1500 kHz SSM, SYNC_IN = VDD Class D Spreading Bandwidth UNITS dB 0.3 MONO Gain Offset (Note 5) Maximum Capacitive Load TYP 1150 SSM mode, SYNC_IN = VDD SYNC_IN Frequency Lock Range ±50 1000 Output Offset Voltage VOS OUT_+ to OUT_- Click-and-Pop Level KCP Peak voltage, A-weighted, 32 samples per second (Note 6) kHz 14 Into shutdown 47 Out of shutdown 50 FS0 = 0 FS1 = 0 800 FS0 = 0 FS1 = 1 1066.7 FS0 = 1 FS1 = 0 1600 FS0 = 1 FS1 = 1 2133.3 mV dBV CROSSOVER FILTERS Cutoff Frequency Accuracy Crossover Frequency Left-to-Right Cutoff Frequency Tracking (Note 7) fXO ±15 ±0.5 % Hz % _______________________________________________________________________________________ 3 MAX9706/MAX9707 ELECTRICAL CHARACTERISTICS (continued) MAX9706/MAX9707 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 = 1µF to GND, C1 = 1µF, C2 = 1µF. TA = TMIN to TMAX, unless otherwise noted. Typical values at TA = +25°C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP 35 50 MAX UNITS HEADPHONE AMPLIFIERS (MAX9706) (HPS = VDD) Output Power Total Harmonic Distortion Plus Noise Signal-to-Noise Ratio POUT THD+N SNR HPVDD = 3.3V to 5V, TA = +25°C, THD+N = 1% (Notes 2, 7) RL = 32Ω mW RL = 16Ω 95 VOUT = 1VRMS, f = 1kHz, bandwidth = 22Hz to 22kHz RL = 32Ω 0.02 RL = 16Ω 0.04 VOUT = 1VRMS Bandwidth = 22Hz to 22kHz 96 A-weighted 100 % HPVDD = 3V to 5.5V Power-Supply Rejection Ratio PSRR Headphone Path Gain (Note 8) Output Offset Voltage VOSHP Crosstalk 70 f = 1kHz, 100mVP-P ripple (Note 3) 80 65 GAIN2 = 0 0 GAIN2 = 1 3 ±0.7 CL dB dB ±3 mV HPL to HPR, HPR to HPL, fIN = 1kHz, POUT = 32mW, RL = 32Ω -60 dB 0.5 V/µs No sustained oscillations 300 pF Slew Rate Maximum Capacitive Load 90 f = 20kHz, 100mVP-P ripple (Note 3) HP_ to GND, TA = +25°C dB HPS Pullup Impedance 600 kΩ Debounce Time 65 ms 1.4 kΩ fOSC / 2 kHz HPS = GND or SHDN = GND Output Impedance in Shutdown Charge-Pump Switching Frequency Click-and-Pop Level fCP KCP Peak voltage, A-weighted, 32 samples per second (Note 6) Into shutdown 52 Out of shutdown 52 dBV LINE-LEVEL MONO OUTPUT (MONO_OUT) MONO_OUT Signal-Path Gain 0 Maximum Output Level Total Harmonic Distortion Plus Noise Ω 1 VRMS VOUT = 1VRMS, fIN = 100Hz, RL = 10kΩ, bandwidth = 22Hz to 22kHz 0.01 % Maximum Capacitive Load No sustained oscillations 200 pF 4 RL = 10kΩ THD+N CL dB 0.1 Output Impedance _______________________________________________________________________________________ 3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover (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 = 1µF to GND, C1 = 1µF, C2 = 1µF. TA = TMIN to TMAX, unless otherwise noted. Typical values at TA = +25°C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS DIGITAL INPUTS (GAIN1, GAIN2, FS0, FS1, SHDN, SYNC_IN, MGAIN) Input-Voltage High VINH Input-Voltage Low VINL 2 Input Leakage Current GAIN1, GAIN2, FS0, FS1, SHDN Input Current SYNC_IN, MGAIN Pullup Impedance SYNC_IN, MGAIN V 0.8 V ±1 µA ±50 200 µA kΩ DIGITAL OUTPUT (SYNC_OUT) Output-Voltage High VOH IOH = 1mA Output-Voltage Low VOL IOL = 1mA Note 1: Note 2: Note 3: Note 4: VDD x 0.9 V VDD x 0.1 V All devices are 100% tested at TA = +25°C. 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 8Ω resistive load in series with a 68µH inductive load connected across BTL output. Headphone mode testing performed with a 32Ω 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. _______________________________________________________________________________________ 5 MAX9706/MAX9707 ELECTRICAL CHARACTERISTICS (continued) 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 = 1µF to GND, 1µF capacitor between C1P and C1N, CVSS = 1µF. TA = TMIN to TMAX, unless otherwise noted. Typical values at TA = +25°C.) VDD = 5V RL = 4Ω OUTPUT POWER = 1.5W VDD = 5V RL = 8Ω OUTPUT POWER = 900mW 0.1 OUTL AND OUTR 0.1 0.01 OUTM 1k 10k 100k 100 1k 10k 0 100k 0.5 1.0 1.5 2.0 2.5 3.0 FREQUENCY (Hz) OUTPUT POWER (W) TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER fIN = 2kHz 0.1 fIN = 200Hz MAX9706 toc05 1 SYNC_IN = FLOAT 0.1 0.01 fIN = 10kHz SYNC_IN = VDD 0.9 10 1 SYNC_IN = 2MHz 0.1 0.01 SYNC_IN = GND 0.001 0.6 VDD = 5V RL = 8Ω fIN = 1kHz SYNC_IN = 1.4MHz SYNC_IN = 0.8MHz 0.001 0.3 100 THD+N (%) 1 VDD = 5V RL = 8Ω fIN = 1kHz 10 THD+N (%) 10 0.01 100 MAX9706 toc06 FREQUENCY (Hz) VDD = 5V RL = 8Ω 0 0.1 0.001 10 MAX9706 toc04 100 100 fIN = 2kHz fIN = 200Hz fIN = 10kHz 0.001 10 1 0.01 OUTM 0.001 VDD = 5V RL = 4Ω 10 THD+N (%) OUTL AND OUTR 0.01 1.2 OUTPUT POWER (W) 6 100 1 THD+N (%) THD+N (%) 1 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER MAX9706 toc03 10 MAX9706 toc01 10 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY MAX9706 toc02 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY THD+N (%) MAX9706/MAX9707 3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover 1.5 1.8 0.001 0 0.5 1.0 OUTPUT POWER (W) 1.5 2.0 0 0.5 1.0 OUTPUT POWER (W) _______________________________________________________________________________________ 1.5 2.0 3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover OUTPUT POWER vs. SUPPLY VOLTAGE 2.0 1.5 THD+N = 1% 2.5 2.0 1.0 1.0 0.5 0.5 0 THD+N = 1% 4.9 5.1 POWER-SUPPLY REJECTION RATIO vs. FREQUENCY PSRR (dB) 50 40 30 POUT = POUTL + POUTR + POUTM fIN = 800Hz 0 1 2 3 OUTPUT POWER (W) 4 OUTL OUTR 5.1 5.3 5.5 0 SSM MODE VOUT = -60dB f = 1kHz RL = 8Ω UNWEIGHTED -20 -40 -60 -80 -100 -120 -110 -120 5 4.9 OUTPUT FREQUENCY SPECTRUM -90 -100 20 10 OUTM -40 -50 -60 -70 -80 4.7 SUPPLY VOLTAGE (V) VRIPPLE = 100mVP-P RL = 8Ω -30 60 THD+N = 1% 4.5 MAX9706 toc11 MAX9706 toc10 0 -10 -20 RL = 4Ω RL = 8Ω 70 1.0 5.5 5.3 EFFICIENCY vs. OUTPUT POWER 80 0 4.7 SUPPLY VOLTAGE (V) 90 1.5 0 4.5 LOAD RESISTANCE (Ω) 100 THD+N = 10% 2.0 0.5 OUTPUT MAGNITUDE (dBV) 100 10 f = 1kHz RL = 8Ω 2.5 0 1 EFFICIENCY (%) 3.0 1.5 3.0 MAX9706 toc12 2.5 THD+N = 10% OUTPUT POWER (W) THD+N = 10% OUTPUT POWER (W) OUTPUT POWER (W) 3.0 f = 1kHz RL = 4Ω 3.5 MAX9706 toc08 VDD = 5V f = 1kHz 3.5 4.0 MAX9706 toc07 4.0 OUTPUT POWER vs. SUPPLY VOLTAGE MAX9706 toc09 OUTPUT POWER vs. LOAD RESISTANCE -140 10 100 1k FREQUENCY (Hz) 10k 100k 0 5 10 15 20 FREQUENCY (kHz) _______________________________________________________________________________________ 7 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 = 1µF to GND, 1µF capacitor between C1P and C1N, CVSS = 1µF. TA = TMIN to TMAX, unless otherwise noted. Typical values at TA = +25°C.) 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 = 1µF to GND, 1µF capacitor between C1P and C1N, CVSS = 1µF. TA = TMIN to TMAX, unless otherwise noted. Typical values at TA = +25°C.) -80 -100 -120 MAX9706 toc14 -10 -20 -30 -40 -50 5 10 -50 -80 0 1 10 100 1000 0 1 FREQUENCY (MHz) TURN-ON/-OFF RESPONSE 20 fXO = 800Hz 100 1000 AMPLITUDE vs. FREQUENCY 20 0 -10 -20 0 -10 -20 -30 -30 -40 -40 -50 fXO = 2.1kHz 10 AMPLITUDE (dBV) 200mA/div AMPLITUDE (dBV) 10 2V/div 10 FREQUENCY (MHz) AMPLITUDE vs. FREQUENCY MAX9706 toc16 -50 10 100 1k FREQUENCY (Hz) 8 -40 -70 FREQUENCY (kHz) 20ms/div -30 -60 20 15 -20 -70 MAX9706 toc17 0 0 -10 -60 -80 -140 RBW = 10kHz INPUT AC-GROUNDED 10 MAX9706 toc18 -60 0 20 OUTPUT AMPLITUDE (dBV) -40 RBW = 10kHz INPUT AC-GROUNDED 10 OUTPUT AMPLITUDE (dBV) SSM MODE VOUT = -60dB f = 1kHz RL = 8Ω A-WEIGHTED -20 20 MAX9706 toc13 0 WIDEBAND OUTPUT SPECTRUM (SSM MODE) MAX9706 toc15 WIDEBAND OUTPUT SPECTRUM (FFM MODE) OUTPUT FREQUENCY SPECTRUM OUTPUT MAGNITUDE (dBV) MAX9706/MAX9707 3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover 10k 100k 10 100 1k FREQUENCY (Hz) _______________________________________________________________________________________ 10k 100k 3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover HPVDD = 3.3V RL = 16Ω HPVDD = 3.3V RL = 32Ω 10 OUTPUT POWER = 25mW 0.1 0.01 0.1 OUTPUT POWER = 10mW 0.01 OUTPUT POWER = 75mW HPVDD = 5V RL = 16Ω 1 THD+N (%) 1 THD+N (%) THD+N (%) 1 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY MAX9706 toc21 10 MAX9706 toc19 10 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY MAX9706 toc20 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY OUTPUT POWER = 20mW 0.1 0.01 OUTPUT POWER = 80mW OUTPUT POWER = 35mW 0.001 0.001 1k 10k 100k 1k 10k 100k 10 100 1k 10k 100k 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 0.01 100 1 fIN = 1kHz 0.1 fIN = 200Hz 0.01 HPVDD = 3.3V RL = 32Ω 10 THD+N (%) 10 THD+N (%) OUTPUT POWER = 10mW HPVDD = 3.3V RL = 16Ω MAX9706 toc24 FREQUENCY (Hz) 1 THD+N (%) 100 FREQUENCY (Hz) HPVDD = 5V RL = 32Ω 0.1 0.001 10 MAX9706 toc23 10 100 MAX9706 toc22 10 1 fIN = 1kHz 0.1 fIN = 10kHz 0.01 fIN = 10kHz OUTPUT POWER = 35mW fIN = 200Hz 0.001 0.001 10 100 1k FREQUENCY (Hz) 10k 100k 0.001 0 15 30 45 60 75 90 105 120 135 OUTPUT POWER (mW) 0 10 20 30 40 50 60 70 OUTPUT POWER (mW) _______________________________________________________________________________________ 9 MAX9706/MAX9707 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 = 1µF to GND, 1µF capacitor between C1P and C1N, CVSS = 1µF. TA = TMIN to TMAX, unless otherwise noted. Typical values at TA = +25°C.) 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 = 1µF to GND, 1µF capacitor between C1P and C1N, CVSS = 1µF. TA = TMIN to TMAX, unless otherwise noted. Typical values at TA = +25°C.) fIN = 10kHz 0.1 fIN = 1kHz 0.01 1 fIN = 10kHz 0.1 140 fIN = 1kHz 100 THD+N = 10% 80 60 40 0.01 20 fIN = 200Hz fIN = 200Hz 0.001 20 40 60 80 100 120 10 20 30 40 0 50 60 OUTPUT POWER (mW) OUTPUT POWER vs. LOAD RESISTANCE OUTPUT POWER vs. HEADPHONE SUPPLY VOLTAGE THD+N = 1% THD+N = 10% 60 40 0 110 VRIPPLE ON VDD AND HPVDD = 100mVP-P INPUTS AC-GROUNDED -20 RL = 16Ω -40 PSRR (dB) 100 90 70 LEFT -60 -80 RL = 32Ω 50 THD+N = 1% 20 10 100 LOAD RESISTANCE (Ω) 1000 RIGHT -100 -120 30 0 1000 100 POWER-SUPPLY REJECTION RATIO vs. FREQUENCY MAX9706 toc29 120 130 OUTPUT POWER (mW) HPVDD = 5V f = 1kHz 10 70 LOAD RESISTANCE (Ω) OUTPUT POWER (mW) 140 80 0 MAX9706 toc28 0 THD+N = 1% MAX9706 toc30 0.001 10 HPVDD = 3.3V f = 1kHz 120 MAX9706 toc27 10 THD+N (%) 1 HPVDD = 5V RL = 32Ω OUTPUT POWER (mW) HPVDD = 5V RL = 16Ω 10 THD+N (%) 100 MAX9706 toc25 100 OUTPUT POWER vs. LOAD RESISTANCE TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER MAX9706 toc26 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER OUTPUT POWER (mW) MAX9706/MAX9707 3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover 3.0 3.5 4.0 4.5 HPVDD (V) 5.0 5.5 10 100 1k FREQUENCY (Hz) ______________________________________________________________________________________ 10k 100k 3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover VRIPPLE = 100mVP-P INPUTS AC-GROUNDED -20 RL = 32Ω POUT = 32mW -10 CROSSTALK (dB) PSRR (dB) -60 RIGHT -80 -30 -40 LEFT TO RIGHT -50 -60 -100 -120 1k 10k 100k 100 30 HPS = GND HPVDD = 3.3V 20 HPS = VDD VDD = 5V 10 1k 10k 50 C1 = C2 = 0.22µF 100k 15 20 25 30 35 40 45 FREQUENCY (Hz) LOAD (Ω) OUTPUT FREQUENCY SPECTRUM TURN-ON/-OFF RESPONSE 50 MAX9706 toc36 0 VOUT = -60dBV f = 1kHz RL = 32Ω -20 OUTPUT MAGNITUDE (dBV) SUPPLY CURRENT (mA) MAX9706 toc34 SUPPLY CURRENT vs. SUPPLY VOLTAGE SUPPLY VOLTAGE = IVDD + IHPVDD 60 20 10 FREQUENCY (Hz) 40 70 MAX9706 toc35 100 C1 = C2 = 0.47µF 30 RIGHT TO LEFT -80 10 80 40 -70 LEFT f = 1kHz THD+N = 1% C1 = C2 = 1µF 90 OUTPUT POWER (mW) -20 -40 100 MAX9706 toc32 0 MAX9706 toc31 0 OUTPUT POWER vs. CHARGE-PUMP CAPACITANCE CROSSTALK vs. FREQUENCY MAX9706 toc33 POWER-SUPPLY REJECTION RATIO vs. FREQUENCY -40 2V/div -60 -80 1V/div -100 -120 -140 0 3.0 3.5 4.0 4.5 SUPPLY VOLTAGE (V) 5.0 5.5 0 5 10 15 20 100ms/div FREQUENCY (kHz) ______________________________________________________________________________________ 11 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 = 1µF to GND, 1µF capacitor between C1P and C1N, CVSS = 1µF. TA = TMIN to TMAX, unless otherwise noted. Typical values at TA = +25°C.) MAX9706/MAX9707 3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover Pin Description PIN NAME FUNCTION MAX9706 MAX9707 1 1 BIAS Internal Bias. Bypass BIAS to GND with a 1µF capacitor. 2 2 GND Ground. Star connect to PGND (see the Supply Bypassing, Layout, and Grounding section). 3 3 VDD Main Power Supply. Connect VDD to a low-noise 5V source. Bypass VDD to GND with a 1µF capacitor. 4 4 5, 23, 31 5, 23, 31 6 7 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 Power Ground. PGND is the ground connection for the speaker amplifiers. 6 OUTL- Left-Speaker Negative Terminal 7 OUTL+ Left-Speaker Positive Terminal 8, 20, 34 8, 20, 34 PVDD Output Power Supply. PVDD is the power connection for the speaker amplifiers. Connect to VDD. Bypass each PVDD to its corresponding PGND with a 1µF capacitor. 9 — CPVDD Charge-Pump Positive Supply. Connect CPVDD to HPVDD. Bypass CPVDD to CPGND with a 1µF capacitor. 10 — C1P Charge-Pump Flying Capacitor Positive Terminal. Connect a 1µF capacitor from C1P to C1N. 11 — CPGND 12 — C1N 13 — CPVSS 14 14 SYNC_IN 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. 15 — HPS 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. 12 Charge-Pump Ground. Connect to PGND. Charge-Pump Flying Capacitor Negative Terminal. Connect a 1µF capacitor from C1N to C1P. Negative Supply Charge-Pump Output. Bypass CPVSS to PGND with a 1µF capacitor. Connect CPVSS to VSS. 16 — VSS Headphone Amplifier Negative Supply. Connect VSS to CPVSS. 17 — HPR Right Headphone Output 18 — HPL Left Headphone Output 19 — HPVDD Positive Supply for Headphone Amplifiers. Connect HPVDD to VDD. Bypass HPVDD to PGND with a 0.1µF capacitor. 21 21 OUTR+ Right-Speaker Positive Terminal 22 22 OUTR- 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. 24 24 SHDN 25 25 FS0 26 26 FS1 Crossover Frequency Select. Connect FS0 and FS1 to GND or VDD to set the crossover frequency. See Table 4. ______________________________________________________________________________________ 3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover PIN NAME FUNCTION MAX9706 MAX9707 27 27 INR 28 28 MGAIN 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. 29 29 GAIN2 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. 30 30 GAIN1 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. 32 32 OUTM- Mono-Speaker Negative Terminal 33 33 OUTM+ Mono-Speaker Positive Terminal 35 35 MONO_OUT Mono Line-Level Output. MONO_OUT is the monaural output of the summed left and right lowfrequency signals. 36 36 INL Left-Channel Audio Input. Connect the left-channel audio signal to INL with a series capacitor. INL has a 25kΩ typical input impedance. — 9–13, 16–19 N.C. No Connection. Not internally connected. — 15 I.C. Internally Connected. Connect to GND. EP EP EP 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. Right-Channel Audio Input. Connect the right-channel audio signal to INR with a series capacitor. INR has a 25kΩ typical input impedance. 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 4Ω 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 16Ω from a 3.3V supply, and are protected against ESD up to ±8kV. MAX9706 MAX9707 HPF CLASS D AMPLIFIER LPF CLASS D AMPLIFIER HPF CLASS D AMPLIFIER LEFT IN RIGHT IN Figure 1. Speaker Arrangement ______________________________________________________________________________________ 13 MAX9706/MAX9707 Pin Description (continued) MAX9706/MAX9707 3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover Class D Speaker Amplifier Operating Modes 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. 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 tSW tSW Table 1. Operating Modes SYNC_IN MODE GND FFM with fOSC = 1100kHz FLOAT FFM with fOSC = 1340kHz VDD SSM with fOSC = 1150kHz ±50kHz Clocked FFM with fOSC = external clock frequency tSW tSW VIN_- VIN_+ OUT_- OUT_+ tON(MIN) VOUT_+ - VOUT_- Figure 3. Output with an Input Signal Applied (SSM Mode) ______________________________________________________________________________________ 15 MAX9706/MAX9707 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. 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. 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. 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. Table 2. Speaker Gain SPEAKER GAIN (dB) MAX9706 HEADPHONE GAIN (dB) 0 +9 0 1 +10.5 0 0 +12 +3 1 +13.5 +3 GAIN2 GAIN1 0 0 1 1 100 VIN_ = 0V 90 80 OUT_- EFFICIENCY (%) MAX9706/MAX9707 3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover MAX9706 POUT PER CHANNEL 70 60 50 40 30 OUT_+ 20 VDD = 5V fIN = 1kHz RL = 8Ω CLASS AB TOTAL POUT 10 0 0 VOUT_+ - VOUT_- = 0V Figure 4. Outputs with No Input Signal 16 0.2 0.4 0.6 0.8 OUTPUT POWER (W) Figure 5. Efficiency vs. Class AB Efficiency ______________________________________________________________________________________ 1.0 1.2 3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover MAX9706/MAX9707 MGAIN MONO SPEAKER GAIN OFFSET (dB) GND -4.5 FLOATING -6.0 VDD -7.5 Table 4. Crossover Frequency Selection FS0 FS1 CROSSOVER FREQUENCY (fXO) (Hz) 0 0 800 0 1 1066.7 1 0 1600 1 1 2133.3 AMPLITUDE (dB) Table 3. Mono Speaker Gain HP FUNCTION 2nd-ORDER SLOPE LP FUNCTION 2nd-ORDER SLOPE FREQUENCY (Hz) fX Figure 6. Crossover Frequency Mono Output Headphone Amplifier (MAX9706) 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 (8Ω L/R, 4Ω 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. 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. Crossover Frequency 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 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. The MAX9706 offers 0dB and 3dB headphone amplifier gain settings controlled through the GAIN2 gain-select input (see Table 2). ______________________________________________________________________________________ 17 (220µF, 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 32Ω load, results in less than 53µA of DC current flow to the headphones. VDD VDD / 2 GND CONVENTIONAL AMPLIFIER BIASING SCHEME 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) 2) +VDD 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. SGND 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. -VDD DirectDrive AMPLIFIER BIASING SCHEME Figure 7. Traditional Amplifier Output vs. MAX9706 DirectDrive Output 0 -5 ATTENUATION (dB) MAX9706/MAX9707 3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover -10 -15 DirectDrive 330µF 220µF 100µF 33µF -20 -25 -30 RL = 16Ω -35 10 100 FREQUENCY (Hz) Figure 8. Low-Frequency Rolloff 18 ______________________________________________________________________________________ 1000 3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover 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. VDD MAX9706 600kΩ SHDN SHUTDOWN CONTROL HPS HPL HPR 1.4kΩ 1.4kΩ 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 50µs then turns back on. If the overload condition is still present after 50µs, 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 +150°C. When the die cools down to +143°C, the device is enabled. The outputs pulsate as the temperature fluctuates between the thermal limits. Shutdown The MAX9706/MAX9707 feature a 0.1µA 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 1.4kΩ. 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 >10µH. Typical 8Ω speakers for portable audio applications exhibit series inductances in the 20µH to 100µH range. Figure 9. HPS Configuration ______________________________________________________________________________________ 19 MAX9706/MAX9707 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 600kΩ pullup. When driving HPS from an external logic source, drive HPS low when the MAX9706 is shut down. Place a 10kΩ resistor in series with HPS and the headphone jack to ensure high ESD protection. MAX9706/MAX9707 3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover Power Supplies Supply Bypassing, Layout, and Grounding 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. 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. 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 2π × RIN × 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 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 1µF capacitor in parallel with a 0.1µF capacitor to PGND. Bypass VDD and PVDD with a 1µF 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 1µF capacitor to GND. ______________________________________________________________________________________ 3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover SUPPLIER PHONE FAX Taiyo Yuden 800-348-2496 847-925-0899 www.t-yuden.com TDK 807-803-6100 847-390-4405 www.component.tdk.com Charge-Pump Capacitor Selection (MAX9706) Use capacitors with an ESR less than 100mΩ 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 1µF, the on-resistance of the switches and the ESR of C1 and C2 dominate. WEBSITE 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. ______________________________________________________________________________________ 21 MAX9706/MAX9707 Table 5. Suggested Capacitor Manufacturers 3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover MAX9706/MAX9707 Functional Diagram/Typical Operating Circuits 4.5V TO 5.5V CBIAS 1µF 1µF 10µF* 1µF BIAS VDD PVDD 1 3 8, 20, 34 BIAS GENERATOR MAX9706 VDD SYNC_IN 14 CIN 0.47µF INL 36 4 SYNC_OUT OSCILLATOR AND SAWTOOTH CLASS D MODULATOR AND H-BRIDGE LOWPASS/ HIGHPASS FILTER CLASS D MODULATOR AND H-BRIDGE MGAIN 28 CIN 0.47µF INR 27 LOWPASS/ HIGHPASS FILTER HPVDD SHDN 24 CLASS D MODULATOR AND H-BRIDGE 7 OUTL+ 6 OUTL- 33 OUTM+ 32 OUTM- 21 OUTR+ 22 OUTR- FS1 26 FS0 25 15 HPS CONTROL GAIN1 30 GAIN2 29 18 HPL INL HPVDD 19 CPVDD 9 C1P 10 1µF 0.1µF C1 1µF C1N 12 17 HPR INR CHARGE PUMP CPGND 11 35 MONO_OUT 13 16 2 5, 23, 31 CPVSS VSS GND PGND C2 1µF *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 4.5V TO 5.5V 1µF 10µF* 1µF VDD PVDD 3 8, 20, 34 VDD MAX9707 SYNC_IN 14 4 SYNC_OUT OSCILLATOR AND SAWTOOTH CIN 0.47µF INL 36 CLASS D MODULATOR AND H-BRIDGE MGAIN 28 CIN 0.47µF LOWPASS/ HIGHPASS FILTER INR 27 7 OUTL+ CLASS D MODULATOR AND H-BRIDGE LOWPASS/ HIGHPASS FILTER CLASS D MODULATOR AND H-BRIDGE SHDN 24 6 OUTL- 33 OUTM+ 32 OUTM- 21 OUTR+ 22 OUTR- FS1 26 FS0 25 CONTROL GAIN1 30 35 MONO_OUT GAIN2 29 BIAS GENERATOR 15 I.C. 9 N.C. 10 N.C. 11 N.C. 12 13 16 17 18 19 N.C. N.C. N.C. N.C. N.C. N.C. 1 BIAS 2 5, 23, 31 GND PGND CBIAS 1µF *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. ______________________________________________________________________________________ 23 MAX9706/MAX9707 Functional Diagram/Typical Operating Circuits (continued) 3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover 27 26 25 24 23 22 21 20 19 27 26 25 24 23 22 21 20 19 GAIN1 PGND 30 16 31 15 OUTMOUTM+ 32 PVDD MONO_OUT INL 34 12 35 11 C1N CPGND 36 10 C1P 14 MAX9706 5 6 7 18 29 17 VSS HPS GAIN1 PGND 30 16 31 15 OUTMOUTM+ 32 PVDD 34 12 MONO_OUT INL 35 11 SYNC_IN N.C. N.C. N.C. 36 10 N.C. SYNC_IN CPVSS 8 9 1 6mm x 6mm TQFN 14 MAX9707 33 BIAS 4 28 PVDD 3 MGAIN GAIN2 CPVDD 2 GND VDD SYNC_OUT PGND OUTLOUTL+ BIAS 1 13 HPL HPR 4 5 6 13 2 3 7 8 9 N.C. 17 PVDD 18 29 VDD SYNC_OUT PGND OUTLOUTL+ 28 GND MGAIN GAIN2 33 SHDN PGND OUTROUTR+ PVDD N.C. INR TOP VIEW FS1 FS0 SHDN PGND OUTROUTR+ PVDD HPVDD INR TOP VIEW FS1 FS0 MAX9706/MAX9707 Pin Configurations N.C. N.C. N.C. I.C. 6mm x 6mm TQFN Chip Information TRANSISTOR COUNT: 12,686 PROCESS: BICMOS 24 ______________________________________________________________________________________ 3-Channel, 2.3W, Filterless Class D Amplifiers with Active Crossover QFN THIN.EPS (NE-1) X e E E/2 k D/2 CL (ND-1) X e D D2 D2/2 e b E2/2 L CL k E2 e L CL CL L1 L L e A1 A2 e 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 © 2005 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products, Inc. MAX9706/MAX9707 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.)