MAX9751ETI

19-3006; Rev 0; 1/04 2.6W Stereo Audio Power Amplifiers and DirectDrive Headphone Amplifiers General Description The MAX9750/MAX9751/MAX9755 combine a stereo, 2.6W audio power amplifier and stereo DirectDrive 110mW headphone amplifier in a single device. The headphone amplifier uses Maxim’s patented DirectDrive architecture that produces a ground-referenced output from a single supply, eliminating the need for large DCblocking capacitors, saving cost, space, and component height. A high 90dB PSRR and low 0.01% THD+N ensures clean, low-distortion amplification of the audio signal. The MAX9750 features an analog volume control, and a BEEP input. The MAX9751 features a 2:1 input multiplexer, allowing multiple audio sources to be selected. All devices feature a single-supply voltage, a shutdown mode, logicselectable gain, and a headphone sense input. Industryleading click-and-pop suppression eliminates audible transients during power and shutdown cycles. The MAX9750/MAX9751/MAX9755 are offered in spacesaving, thermally efficient 28-pin thin QFN (5mm x 5mm x 0.8mm) and 28-pin TSSOP-EP packages. Both devices have thermal-overload and output short-circuit protection, and are specified over the extended -40°C to +85°C temperature range. Features ♦ No DC-Blocking Capacitors Required—Provides Industry’s Most Compact Notebook Audio Solution ♦ PC2001 Compliant ♦ 5V Single-Supply Operation ♦ Class AB 2.6W Stereo BTL Speaker Amplifiers ♦ 110mW DirectDrive Headphone Amplifiers ♦ High 90dB PSRR ♦ Low-Power Shutdown Mode ♦ Industry-Leading Click-and-Pop Suppression ♦ Low 0.01% THD+N at 1kHz ♦ Short-Circuit and Thermal Protection ♦ Selectable Gain Settings ♦ Analog Volume Control (MAX9750) ♦ Beep Input with Glitch Filter (MAX9750) ♦ 2:1 Stereo Input MUX (MAX9751) ♦ ±8kV ESD-Protected Headphone Driver Outputs ♦ Available in Space-Saving, Thermally Efficient Packages 28-Pin Thin QFN (5mm x 5mm x 0.8mm) 28-Pin TSSOP-EP MAX9750/MAX9751/MAX9755 Applications Notebook PCs Tablet PCs Portable DVD Flat-Panel TVs PC Displays LCD Projectors Simplified Block Diagrams PART MAX9750AETI*† MAX9750BETI*† MAX9750BEUI* MAX9750CETI† MAX9751ETI*† MAX9751EUI*† VOL † Ordering Information TEMP RANGE PINPACKAGE MAXIMUM GAIN (dB) 13.5 13.5 19.5 19.5 10.5 10.5 10.5 10.5 10.5 10.5 -40°C to +85°C 28 Thin QFN -40°C to +85°C 28 Thin QFN -40°C to +85°C 28 TSSOP-EP** -40°C to +85°C 28 Thin QFN -40°C to +85°C 28 Thin QFN -40°C to +85°C 28 TSSOP-EP** -40°C to +85°C 28 Thin QFN -40°C to +85°C 28 TSSOP-EP** MAX9750AEUI*† -40°C to +85°C 28 TSSOP-EP** MAX9750CEUI*† -40°C to +85°C 28 TSSOP-EP** MAX9755AETI*† MAX9755AEUI* † BEEP *Future product—contact factory for availability. **EP = Exposed Paddle. †Lead-free MAX9750 package. Simplifed Block Diagrams continued at end of data sheet. ________________________________________________________________ Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 2.6W Stereo Audio Power Amplifiers and DirectDrive Headphone Amplifiers MAX9750/MAX9751/MAX9755 ABSOLUTE MAXIMUM RATINGS Supply Voltage (VDD, PVDD, HPVDD, CPVDD to GND)..........+6V GND to PGND.....................................................................±0.3V CPVSS, C1N, VSS to GND .........................-6.0V to (GND + 0.3V) HPOUT_ to GND ....................................................................±3V Any Other Pin .............................................-0.3V to (VDD + 0.3V) Duration of OUT_ Short Circuit to GND or PVDD ........Continuous Duration of OUT_+ Short Circuit to OUT_- .................Continuous Duration of HPOUT_ Short Circuit to GND, VSS or HPVDD .........................................................Continuous Continuous Current (PVDD, OUT_, PGND) ...........................1.7A Continuous Current (CPVDD, C1N, C1P, CPVSS, VSS, HPVDD, HPOUT_) .......................................................................850mA Continuous Input Current (All Other Pins) ........................±20mA Continuous Power Dissipation (TA = +70°C) 28-Pin Thin QFN (derate 20.8mW/°C above +70°C) ..1667mW 28-Pin TSSOP-EP (derate 23.8mW/°C above +70°C).1904mW 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 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 = CPVDD = HPVDD = 5V, GND = PGND = CPGND = 0V, SHDN = VDD, CBIAS = 1µF, C1 = C2 = 1µF, speaker load terminated between OUT_+ and OUT_-, headphone load terminated between HPOUT_ and GND, MAX9750: GAIN1 = GAIN2 = VOL = RL = 33kΩ = GND, MAX9751/MAX9755: GAIN = VDD = IN1/2 = GND, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER GENERAL Supply Voltage Range Headphone Supply Voltage Quiescent Supply Current Shutdown Supply Current Bias Voltage Switching Time Input Resistance Turn-On Time SPEAKER AMPLIFIER (HPS = GND) Output Offset Voltage Power-Supply Rejection Ratio (Note 3) VOS PSRR Measured between OUT_+ - OUT_PVDD or VDD = 4.5V to 5.5V (TA = +25°C) f = 1kHz, VRIPPLE = 200mVP-P f = 10kHz, VRIPPLE = 200mVP-P 75 ±0.4 90 80 55 dB ±6 mV VDD, PVDD CPVDD, HPVDD IDD ISHDN VBIAS tSW RIN tSON Gain or input switching Amplifier inputs (Note 2) 10 Inferred from PSRR test Inferred from PSRR test HPS = GND, speaker mode, RL = ∞ HPS = VDD, headphone mode, RL = ∞ SHDN = GND 1.7 4.5 3 14 7 0.2 1.8 10 20 25 30 5.5 5.5 29 13 5 1.9 V V mA µA V µs kΩ ms SYMBOL CONDITIONS MIN TYP MAX UNITS 2 _______________________________________________________________________________________ 2.6W Stereo Audio Power Amplifiers and DirectDrive Headphone Amplifiers ELECTRICAL CHARACTERISTICS (continued) (VDD = PVDD = CPVDD = HPVDD = 5V, GND = PGND = CPGND = 0V, SHDN = VDD, CBIAS = 1µF, C1 = C2 = 1µF, speaker load terminated between OUT_+ and OUT_-, headphone load terminated between HPOUT_ and GND, MAX9750: GAIN1 = GAIN2 = VOL = RL = 33kΩ = GND, MAX9751/MAX9755: GAIN = VDD = IN1/2 = GND, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER SYMBOL CONDITIONS MAX9750A/ MAX9750B/ MAX9751/ MAX9755 MAX9750C MAX9750A/ MAX9750B/ MAX9751/ MAX9755 MAX9750C MAX9750A/ MAX9750B/ MAX9751/ MAX9755 MAX9750C 1.2 MIN TYP MAX UNITS MAX9750/MAX9751/MAX9755 RL = 8Ω 1.4 0.65 0.8 Output Power POUT THD+N = 1%, f = 1kHz, TA = +25°C RL = 4Ω 2.3 W 1.5 RL = 3Ω 2.6 2.2 0.01 0.02 90 80 200 75 60 1.4 dB V/µs % dB µVRMS pF Total Harmonic Distortion Plus Noise Signal-to-Noise Ratio Noise Capacitive-Load Drive Crosstalk Slew Rate THD+N SNR Vn CL RL = 8Ω, POUT = 500mW, f = 1kHz RL = 4Ω, POUT = 1W, f = 1kHz RL = 8Ω, POUT = 1W, BW = 22Hz to 22kHz BW = 22Hz to 22kHz, A-weighted No sustained oscillations L to R, R to L, f = 10kHz Any unselected input to any active input, f = 10kHz (MAX9751) SR GAIN1 = 0, GAIN2 = 0 GAIN1 = 1, GAIN2 = 0 MAX9750A GAIN1 = 0, GAIN2 = 1 GAIN1 = 1, GAIN2 = 1 GAIN1 = 0, GAIN2 = 0 GAIN1 = 1, GAIN2 = 0 GAIN1 = 0, GAIN2 = 1 GAIN1 = 1, GAIN2 = 1 GAIN1 = 0, GAIN2 = 0 MAX9750C GAIN1 = 1, GAIN2 = 0 GAIN1 = 0, GAIN2 = 1 GAIN1 = 1, GAIN2 = 1 GAIN = 1 GAIN = 0 9 10.5 12 13.5 15 16.5 18 19.5 6 7.5 9 10.5 9 10.5 dB dB Gain (Maximum Volume Setting) AVMAX(SPKR) MAX9750B Gain (MAX9751/MAX9755) AV _______________________________________________________________________________________ 3 2.6W Stereo Audio Power Amplifiers and DirectDrive Headphone Amplifiers MAX9750/MAX9751/MAX9755 ELECTRICAL CHARACTERISTICS (continued) (VDD = PVDD = CPVDD = HPVDD = 5V, GND = PGND = CPGND = 0V, SHDN = VDD, CBIAS = 1µF, C1 = C2 = 1µF, speaker load terminated between OUT_+ and OUT_-, headphone load terminated between HPOUT_ and GND, MAX9750: GAIN1 = GAIN2 = VOL = RL = 33kΩ = GND, MAX9751/MAX9755: GAIN = VDD = IN1/2 = GND, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER Output Offset Voltage Power-Supply Rejection Ratio (Note 3) SYMBOL VOS PSRR TA = +25°C HPVDD = 3V to 5.5V, TA = +25°C f = 1kHz, VRIPPLE = 200mVP-P f = 10kHz, VRIPPLE = 200mVP-P Output Power Total Harmonic Distortion Plus Noise Signal-to-Noise Ratio Noise Capacitive-Load Drive Crosstalk Slew Rate ESD Gain CHARGE PUMP Charge-Pump Frequency VOLUME CONTROL (MAX9750_) VOL Input Impedance VOL Input Hysteresis Full Mute Input Voltage Channel Matching BEEP INPUT (MAX9750_) Beep Signal Minimum Amplitude Beep Signal Minimum Frequency VBEEP fBEEP 0.8 200 VP-P Hz (Note 4) AV = -25dB to +13.5dB RVOL 100 10 0.858 x HPVDD ±0.2 MΩ mV V dB fOSC 500 550 600 kHz SR ESD AV IEC air discharge GAIN2 = GAIN = 1, GAIN1 = X GAIN2 = GAIN = 0, GAIN1 = X POUT THD+N = 1%, f = 1kHz, TA = +25°C RL = 32Ω RL = 16Ω 40 70 CONDITIONS MIN TYP ±2 75 73 63 50 110 0.007 0.03 95 12 200 88 88 0.4 ±8 0 3 dB V/µs kV dB mW dB MAX ±7 UNITS mV HEADPHONE AMPLIFIER (HPS = VDD) THD+N SNR Vn CL RL = 32Ω, POUT = 20mW, f = 1kHz RL = 16Ω, POUT = 75mW, f = 1kHz RL = 32Ω, POUT = 50mW, BW = 22Hz to 22kHz BW = 22Hz to 22kHz No sustained oscillations L to R, R to L, f = 10kHz Any unselected input to any active input, f = 10kHz (MAX9751) % dB µVRMS pF 4 _______________________________________________________________________________________ 2.6W Stereo Audio Power Amplifiers and DirectDrive Headphone Amplifiers ELECTRICAL CHARACTERISTICS (continued) (VDD = PVDD = CPVDD = HPVDD = 5V, GND = PGND = CPGND = 0V, SHDN = VDD, CBIAS = 1µF, C1 = C2 = 1µF, speaker load terminated between OUT_+ and OUT_-, headphone load terminated between HPOUT_ and GND, MAX9750: GAIN1 = GAIN2 = VOL = RL = 33kΩ = GND, MAX9751/MAX9755: GAIN = VDD = IN1/2 = GND, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER Logic Input High Voltage Logic Input Low Voltage Logic Input Current SYMBOL VIH VIL IIN CONDITIONS MIN 2 0.8 ±1 TYP MAX UNITS V V µA MAX9750/MAX9751/MAX9755 LOGIC INPUT (SHDN, GAIN1, GAIN2, GAIN, VOL, IN1/2, HPS) Note 1: Note 2: Note 3: Note 4: Note 5: All devices are 100% production tested at room temperature. All temperature limits are guaranteed by design. Guaranteed by design. Not production tested. PSRR is specified with the amplifier input connected to GND through CIN. See Table 3 for details of the mute levels. The value of RB dictates the minimum beep signal amplitude (see the Beep Input section). _______________________________________________________________________________________ 5 2.6W Stereo Audio Power Amplifiers and DirectDrive Headphone Amplifiers MAX9750/MAX9751/MAX9755 Typical Operating Characteristics (Measurement BW = 22Hz to 22kHz, TA = +25°C, unless otherwise noted.) TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY (SPEAKER MODE) MAX9750/51 toc01 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY (SPEAKER MODE) MAX9750/51 toc02 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY (SPEAKER MODE) VCC = 5V RL = 8 Ω AV = 10.5dB OUTPUT POWER = 100mW MAX9750/51 toc03 10 1 VCC = 5V RL = 3 Ω AV = 10.5dB OUTPUT POWER = 1.5W 10 1 VCC = 5V RL = 4 Ω AV = 10.5dB OUTPUT POWER = 1.25W 10 1 THD+N (%) THD+N (%) 0.1 0.1 THD+N (%) 0.1 0.01 OUTPUT POWER = 500mW 0.001 0.01 OUTPUT POWER = 500mW 0.001 0.01 OUTPUT POWER = 600mW 0.001 0.0001 10 100 1k FREQUENCY (Hz) 10k 100k 0.0001 10 100 1k FREQUENCY (Hz) 10k 100k 0.0001 10 100 1k FREQUENCY (Hz) 10k 100k TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER (SPEAKER MODE) MAX9750/51 toc04 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER (SPEAKER MODE) MAX9750/51 toc05 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER (SPEAKER MODE) VCC = 5V RL = 8 Ω AV = 10.5dB MAX9750C MAX9750/51 toc06 100 VCC = 5V RL = 3 Ω AV = 10.5dB MAX9750C 100 10 10 VCC = 5V RL = 4 Ω AV = 10.5dB MAX9750C 100 10 THD+N (%) THD+N (%) 1 fIN = 10kHz 0.1 THD+N (%) 1 fIN = 10kHz 0.1 1 0.1 fIN = 10kHz 0.01 fIN = 20Hz 0.001 0 0.5 1.0 1.5 2.0 2.5 3.0 OUTPUT POWER (W) fIN = 1kHz 0.01 fIN = 20Hz 0.001 0 0.5 1.0 1.5 OUTPUT POWER (W) 2.0 fIN = 1kHz 0.01 fIN = 20Hz 0.001 0 0.2 0.4 0.6 0.8 OUTPUT POWER (W) 1.0 1.2 fIN = 1kHz OUTPUT POWER vs. LOAD RESISTANCE (SPEAKER MODE) MAX9750/51 toc07 POWER DISSIPATION vs. OUTPUT POWER (SPEAKER MODE) MAX9750/51 toc08 POWER-SUPPLY REJECTION RATIO vs. FREQUENCY (SPEAKER MODE) -10 -20 -30 PSRR (dB) VRIPPLE = 200mVP-P AV = 10.5dB OUTPUT REFERRED MAX9750/51 toc09 3.0 2.5 OUTPUT POWER (W) 2.0 THD+N = 10% 1.5 1.0 0.5 0 1 10 LOAD RESISTANCE (Ω) THD+N = 1% VCC = 5V f = 1kHz AV = 10.5dB MAX9750C 5 VDD = 5V f = 1kHz POUT = POUTL + POUTR MAX9750C RL = 4 Ω 0 POWER DISSIPATION (mW) 4 3 -40 -50 -60 -70 2 RL = 8 Ω 1 -80 -90 0 100 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 OUTPUT POWER (W) -100 10 100 1k FREQUENCY (Hz) 10k 100k 6 _______________________________________________________________________________________ 2.6W Stereo Audio Power Amplifiers and DirectDrive Headphone Amplifiers MAX9750/MAX9751/MAX9755 Typical Operating Characteristics (continued) (Measurement BW = 22Hz to 22kHz, TA = +25°C, unless otherwise noted.) CROSSTALK vs. FREQUENCY (SPEAKER MODE) -10 -20 CROSSTALK (dB) -30 -40 -50 -60 -70 -80 -90 -100 -110 -120 10 100 1k FREQUENCY (Hz) 10k 100k 20ms/div VCC = 5V VRIPPLE = 200mVP-P RL = 4 Ω MAX9750/51 toc10 TURN-ON RESPONSE (SPEAKER MODE) MAX9750/51 toc11 0 5V/div SHDN OUT_+ AND OUT_- 2V/div LEFT TO RIGHT RIGHT TO LEFT OUT_+ - OUT_RL = 8Ω 100mV/div TURN-OFF RESPONSE (SPEAKER MODE) MAX9750/51 toc12 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY (HEADPHONE MODE) MAX9750/51 toc13 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY (HEADPHONE MODE) VDD = 5V RL = 32Ω AV = 3dB OUTPUT POWER = 45mW THD+N (%) 0.1 MAX9750/51 toc14 10 5V/div VDD = 5V RL = 16Ω AV = 3dB OUTPUT POWER = 90mW THD+N (%) 10 SHDN OUT_+ AND OUT_- 1 1 2V/div 0.1 0.01 OUTPUT POWER = 30mW 0.01 OUTPUT POWER = 10mW OUT_+ - OUT_RL = 8Ω 20mV/div 0.001 0.0001 20ms/div 10 100 1k FREQUENCY (Hz) 10k 100k 0.001 0.0001 10 100 1k FREQUENCY (Hz) 10k 100k TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY (HEADPHONE MODE) MAX9750/51 toc15 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY (HEADPHONE MODE) VDD = 3.3V RL = 32Ω AV = 3dB OUTPUT POWER = 45mW THD+N (%) 0.1 MAX9750/51 toc16 10 VDD = 3.3V RL = 16Ω AV = 3dB OUTPUT POWER = 30mW THD+N (%) 0.1 10 1 1 0.01 OUTPUT POWER = 10mW 0.01 OUTPUT POWER = 10mW 0.001 0.001 0.0001 10 100 1k FREQUENCY (Hz) 10k 100k 0.0001 10 100 1k FREQUENCY (Hz) 10k 100k _______________________________________________________________________________________ 7 2.6W Stereo Audio Power Amplifiers and DirectDrive Headphone Amplifiers MAX9750/MAX9751/MAX9755 Typical Operating Characteristics (continued) (Measurement BW = 22Hz to 22kHz, TA = +25°C, unless otherwise noted.) TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER (HEADPHONE MODE) MAX9750/51 toc17 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER (HEADPHONE MODE) MAX9750/51 toc18 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER (HEADPHONE MODE) VDD = 3.3V RL = 16Ω AV = 3dB MAX9750/51 toc19 1000 100 10 THD+N (%) VDD = 5V R L = 1 6Ω AV = 3dB 1000 100 10 THD+N (%) VDD = 5V RL = 32Ω AV = 3dB 1000 100 10 THD+N (%) fIN = 1kHz 1 1 0.1 0.01 fIN = 10kHz 1 0.1 0.01 0.001 fIN = 1kHz fIN = 10kHz fIN = 20Hz fIN = 20Hz 0.1 0.01 0.001 fIN = 10kHz fIN = 20Hz 0.001 0 25 50 fIN = 1kHz 100 OUTPUT POWER (mW) 75 125 150 0 20 40 60 80 100 0 10 20 30 40 50 60 OUTPUT POWER (mW) OUTPUT POWER (mW) TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER (HEADPHONE MODE) VDD = 3.3V R L = 3 2Ω AV = 3dB MAX9750/51 toc20 OUTPUT POWER vs. LOAD RESISTANCE (HEADPHONE MODE) MAX9750/51 toc21 POWER DISSIPATION vs. OUTPUT POWER (HEADPHONE MODE) 225 POWER DISSIPATION (mW) 200 175 150 125 100 75 50 25 0 MAX9750/51 toc22 1000 100 10 THD+N (%) 1 180 160 140 OUTPUT POWER (mW) 120 100 80 60 40 THD+N = 1% THD+N = 10% 250 RL = 16Ω fIN = 1kHz fIN = 20Hz fIN = 10kHz 0.1 0.01 0.001 0 10 20 60 70 OUTPUT POWER (mW) 30 40 50 80 90 RL = 32Ω VDD = 5V f = 1kHz POUT = POUTL + POUTR 0 25 50 75 100 125 150 175 200 225 250 OUTPUT POWER (mW) 20 0 10 100 LOAD RESISTANCE (Ω) 1000 OUTPUT POWER vs. SUPPLY VOLTAGE (HEADPHONE MODE) MAX9750/51 toc23 POWER-SUPPLY REJECTION RATIO vs. FREQUENCY (HEADPHONE MODE) -10 -20 -30 VRIPPLE = 200mVP-P AV = 10.5dB OUTPUT REFERRED MAX9750/51 toc24 125 RL = 16Ω 100 OUTPUT POWER (mW) 0 RL = 32Ω 50 PSRR (dB) 5.0 5.5 75 -40 -50 -60 -70 25 f = 1kHz 0 3.0 3.5 4.0 4.5 SUPPLY VOLTAGE (V) -80 -90 -100 10 100 1k FREQUENCY (Hz) 10k 100k 8 _______________________________________________________________________________________ 2.6W Stereo Audio Power Amplifiers and DirectDrive Headphone Amplifiers MAX9750/MAX9751/MAX9755 Typical Operating Characteristics (continued) (Measurement BW = 22Hz to 22kHz, TA = +25°C, unless otherwise noted.) CROSSTALK vs. FREQUENCY (HEADPHONE MODE) MAX9750/51 toc25 OUTPUT POWER vs. CHARGE-PUMP CAPACITANCE AND LOAD RESISTANCE MAX9750/51 toc26 HEADPHONE OUTPUT SPECTRUM VDD = 5V f = 1kHz VOUT = -60dB RL = 32Ω MAX9750/51 toc27 0 -20 CROSSTALK (dB) -40 -60 -80 VCC = 5V VRIPPLE = 200mVP-P R L = 3 2Ω 200 180 160 OUTPUT POWER (mW) 140 120 100 80 60 40 C1 = C2 = 1µF 0 -20 MAGNITUDE (dB) -40 -60 -80 -100 -120 -140 VDD = 5V f = 1kHz THD+N = 1% C1 = C2 = 2.2µF RIGHT TO LEFT -100 LEFT TO RIGHT -120 10 100 1k FREQUENCY (Hz) 10k 100k 20 0 10 20 30 40 50 LOAD RESISTANCE (Ω) 0 5 10 FREQUENCY (Hz) 15 20 TURN-ON RESPONSE (HEADPHONE MODE) MAX9750/51 toc28 TURN-OFF RESPONSE (HEADPHONE MODE) MAX9750/51 toc29 5V/div SHDN SHDN 5V/div HPOUT_ 20mV/div HPOUT_ 20mV/div RL = 32Ω 10ms/div RL = 32Ω 10ms/div SUPPLY CURRENT vs. SUPPLY VOLTAGE MAX9750/51 toc30 SHUTDOWN SUPPLY CURRENT vs. SUPPLY VOLTAGE MAX9750/51 toc31 18 16 SUPPLY CURRENT (mA) 14 12 10 8 6 4 2 0 4.50 4.75 5.00 5.25 HPS = VDD HPS = GND 0.35 0.30 SUPPLY CURRENT (µA) 0.25 0.20 0.15 0.10 0.05 0 5.50 4.50 4.75 5.00 5.25 5.50 SUPPLY VOLTAGE (V) SUPPLY VOLTAGE (V) _______________________________________________________________________________________ 9 2.6W Stereo Audio Power Amplifiers and DirectDrive Headphone Amplifiers MAX9750/MAX9751/MAX9755 Pin Description PIN MAX9750 THIN QFN 1 2 3, 19 4 5 6, 16 7 8 9 10 11 12 13 14 15 17 18 20 21 22 23 24 25 26 27 28 — — — — — — — TSSOP 5 6 7, 23 8 9 10, 20 11 12 13 14 15 16 17 18 19 21 22 24 25 26 27 28 1 2 3 4 — — — — — — — MAX9751 THIN QFN — — 3, 19 4 5 6, 16 7 8 9 10 11 12 13 14 15 17 18 20 21 22 — — 25 26 — — 1 2 23 24 27 28 — TSSOP — — 7, 23 8 9 10, 20 11 12 13 14 15 16 17 18 19 21 22 24 25 26 — — 1 2 — — 5 6 27 28 3 4 — MAX9755 THIN QFN 2 — 3, 19 4 5 6, 16 7 8 9 10 11 12 13 14 15 17 18 20 21 22 — — 25 23, 26 28 — — — — 24 — — 1, 27 TSSOP 6 — 7, 23 8 9 10, 20 11 12 13 14 15 16 17 18 19 21 22 24 25 26 — — 1 2, 27 4 — — — — 28 — — 3, 5 INL BEEP PGND OUTL+ OUTLPVDD CPVDD C1P CPGND C1N CPVSS VSS HPOUTR HPOUTL HPVDD OUTROUTR+ HPS BIAS SHDN GAIN2 GAIN1 VDD GND INR VOL INL1 INL2 IN1/2 GAIN INR1 INR2 N.C. Left-Channel Audio Input Audible Alert Beep Input Power Ground Left-Channel Positive Speaker Output Left-Channel Negative Speaker Output Speaker Amplifier Power Supply Charge-Pump Power Supply Charge-Pump Flying-Capacitor Positive Terminal Charge-Pump Ground Charge-Pump Flying-Capacitor Negative Terminal Charge-Pump Output. Connect to VSS. Headphone Amplifier Negative Power Supply Right-Channel Headphone Output Left-Channel Headphone Output Headphone Positive Power Supply Right-Channel Negative Speaker Output Right-Channel Positive Speaker Output Headphone Sense Input Common-Mode Bias Voltage. Bypass with a 1µF capacitor to GND. Shutdown. Drive SHDN low to disable the device. Connect SHDN to VDD for normal operation. Gain Control Input 2 Gain Control Input 1 Power Supply Ground Right-Channel Audio Input Analog Volume Control Input Left-Channel Audio Input 1 Left-Channel Audio Input 2 Input Select Gain Select Right-Channel Audio Input 1 Right-Channel Audio Input 2 No Connection. Not internally connected. NAME FUNCTION 10 ______________________________________________________________________________________ 2.6W Stereo Audio Power Amplifiers and DirectDrive Headphone Amplifiers MAX9750/MAX9751/MAX9755 MAX9750 ONLY IN_ VOUT VDD VDD/2 GND BIAS BIAS OUT_+ CONVENTIONAL DRIVER-BIASING SCHEME +VDD VOL VOLUME CONTROL OUT_ BIAS GND HPOUT_ GND DirectDrive BIASING SCHEME -VDD Figure 1. MAX9750/MAX9751 Signal Path Figure 2. Traditional Headphone Amplifier Output Waveform vs. DirectDrive Headphone Amplifier Output Waveform Detailed Description The MAX9750/MAX9751/MAX9755 combine a 2.6W BTL speaker amplifier and a 110mW DirectDrive headphone amplifier with integrated headphone sensing and comprehensive click-and-pop suppression. The MAX9750 features an analog volume control, BEEP input, and four-level gain control. The MAX9751 features a 2:1 input stereo multiplexer and two-level gain control. All devices feature high 90dB PSRR, low 0.01% THD+N, industry-leading click-pop performance, and a lowpower shutdown mode. Each signal path consists of an input amplifier that sets the gain of the signal path and feeds both the speaker and headphone amplifier (Figure 1). The speaker amplifier uses a BTL architecture, doubling the voltage drive to the speakers and eliminating the need for DCblocking capacitors. The output consists of two signals, identical in magnitude, but 180° out of phase. The headphone amplifiers use Maxim’s patented DirectDrive architecture that eliminates the bulky output DC-blocking capacitors required by traditional headphone amplifiers. A charge pump inverts the positive supply (CPVDD), creating a negative supply (CPVSS). The headphone amplifiers operate from these bipolar supplies with their outputs biased about GND (Figure 2). The amplifiers have almost twice the supply range compared to other single-supply amplifiers, nearly quadrupling the available output power. The benefit of the GND bias is that the amplifier outputs no longer have a DC component (typically VDD / 2). This eliminates the large DC-blocking capacitors required with conventional headphone amplifiers, conserving board space and system cost, and improving frequency response. The MAX9750 features an analog volume control that varies the gain of the amplifiers based on the DC voltage applied at VOL. Both devices feature an undervoltage lockout that prevents operation from an insufficient power supply and click-and-pop suppression that eliminates audible transients on startup and shutdown. The amplifiers include thermal-overload and short-circuit protection, and can withstand ±8kV ESD strikes on the headphone amplifier outputs (IEC air discharge). An additional feature of the speaker amplifiers is that there is no phase inversion from input to output. DirectDrive Conventional single-supply headphone amplifiers have their outputs biased about a nominal DC voltage (typically half the supply) for maximum dynamic range. Large coupling capacitors are needed to block this DC bias from the headphones. Without these capacitors, a 11 ______________________________________________________________________________________ 2.6W Stereo Audio Power Amplifiers and DirectDrive Headphone Amplifiers MAX9750/MAX9751/MAX9755 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 MAX9750/MAX9751/MAX9755 headphone amplifier output to be biased about GND, almost doubling the dynamic range while operating from a single supply. With no DC component, there is no need for the large DC-blocking capacitors. Instead of two large capacitors (220µF typ), the MAX9750/MAX9751/ MAX9755 charge pump requires only two small ceramic capacitors (1µF typ), conserving board space, reducing cost, and improving the frequency response of the headphone amplifier. See the Output Power vs. Charge-Pump Capacitance and Load Resistance graph in the Typical Operating Characteristics for details of the possible capacitor values. Previous attempts to eliminate the output coupling capacitors involved biasing the headphone return (sleeve) to the DC bias voltage of the headphone amplifiers. This method raised some issues: 1) The sleeve is typically grounded to the chassis. Using this biasing approach, the sleeve must be isolated from system ground, complicating product design. 2) During an ESD strike, the amplifier’s ESD structures are the only path to system ground. The amplifier must be able to withstand the full ESD strike. 3) When using the headphone jack as a lineout to other equipment, the bias voltage on the sleeve may conflict with the ground potential from other equipment, resulting in large ground-loop current and possible damage to the amplifiers. Low-Frequency Response In addition to the cost and size disadvantages, the DCblocking capacitors limit the low-frequency response of the amplifier and distort the audio signal: 1) The impedance of the headphone load to the DCblocking capacitor forms a highpass filter with the -3dB point determined by: f−3dB = 1 2πRLCOUT LOW-FREQUENCY ROLLOFF (RL = 16Ω) 0 -3 -6 ATTENUATION (dB) -9 -12 -15 -18 -21 -24 -27 -30 10 100 1k FREQUENCY (Hz) 10k 100k 33µF DirectDrive 330µF 220µF 100µF Figure 3. Low-Frequency Attenuation of Common DC-Blocking Capacitor Values the filter can attenuate low-frequency signals within the audio band. Larger values of COUT reduce the attenuation but are physically larger, more expensive capacitors. Figure 3 shows the relationship between the size of COUT and the resulting low-frequency attenuation. Note that the -3dB point for a 16Ω headphone with a 100µF blocking capacitor is 100Hz, well within the audio band. 2) The voltage coefficient of the capacitor, the change in capacitance due to a change in the voltage across the capacitor, distorts the audio signal. At frequencies around the -3dB point, the reactance of the capacitor dominates, and the voltage coefficient appears as frequency-dependent distortion. Figure 4 shows the THD+N introduced by two different capacitor dielectrics. Note that around the -3dB point, THD+N increases dramatically. The combination of low-frequency attenuation and frequency-dependent distortion compromises audio reproduction. DirectDrive improves low-frequency reproduction in portable audio equipment that emphasizes low-frequency effects such as multimedia laptops, and MP3, CD, and DVD players. Charge Pump The MAX9750/MAX9751/MAX9755 feature a low-noise charge pump. The 550kHz switching frequency is well beyond the audio range, and does not interfere with the audio signals. The switch drivers feature a controlled switching speed that minimizes noise generated by turnon and turn-off transients. Limiting the switching speed of the charge pump minimizes the di/dt noise caused by the where RL is the impedance of the headphone and COUT is the value of the DC-blocking capacitor. The highpass filter is required by conventional single-ended, single-supply headphone amplifiers to block the midrail DC component of the audio signal from the headphones. Depending on the -3dB point, 12 ______________________________________________________________________________________ 2.6W Stereo Audio Power Amplifiers and DirectDrive Headphone Amplifiers MAX9750/MAX9751/MAX9755 ADDITIONAL THD+N DUE TO DC-BLOCKING CAPACITORS 10 VDD MAX9750/ MAX9751/ MAX9755 SHUTDOWN CONTROL HPS TANTALUM 0.01 HPOUTL HPOUTR 1kΩ ALUM/ELEC 0.0001 10 100 1k FREQUENCY (Hz) 10k 100k 1kΩ 20 14 13 10µA 1 THD+N (%) 0.1 0.001 Figure 4. Distortion Contributed by DC-Blocking Capacitors Figure 5. HPS Configuration parasitic bond wire and trace inductance. Although not typically required, additional high-frequency ripple attenuation can be achieved by increasing the size of C2 (see the Typical Application Circuit). Gain Selection MAX9750 The MAX9750 features an internally set, selectable gain. The GAIN1 and GAIN2 inputs set the maximum gain of the MAX9750 speaker and headphone amplifiers (Table 1). The gain of the device can vary based upon the voltage at VOL (see the Analog Volume Control section). However, the maximum gain cannot be exceeded. MAX9751/MAX9755 The gain of the MAX9751/MAX9755 is set by the GAIN input. Driving GAIN high sets the gain of the speaker amplifiers to 9dB and the gain of the headphone amplifiers to 0dB. Driving GAIN low sets the gain of the speaker amplifiers to 10.5dB, and the gain of the headphone amplifiers to 3dB (Table 2). Headphone Sense Input (HPS) The headphone sense input (HPS) monitors the headphone jack and automatically configures the device based upon the voltage applied at HPS. A voltage of less than 0.8V sets the device to speaker mode. A voltage of greater than 2V disables the bridge amplifiers and enables the headphone amplifiers. For automatic headphone detection, connect HPS to the control pin of a 3-wire headphone jack as shown in Figure 5. With no headphone present, the output impedance of the headphone amplifier pulls HPS low. 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 a 10µA current source. Analog Volume Control (VOL) The MAX9750 features an analog volume control that varies the gain of the device in 31 discrete steps based upon the DC voltage applied to VOL. The input range of VVOL is from 0 (full volume) to 0.858 x HPVDD (full mute), with example step sizes shown in Table 3. Connect the reference of the device driving VOL (Figure 6) to HPVDD. Since the volume control ADC is ratiometric to HPVDD, any changes in HPVDD are negated. The gain step sizes are not constant; the step sizes are 0.5dB/step at the upper extreme, 2dB/step in the midrange, and 4dB/step at the lower extreme. Figure 7 shows the transfer function of the volume control for a 3.3V supply. BIAS The MAX9750/MAX9751/MAX9755 feature an internally generated, power-supply independent, common-mode bias voltage of 1.8V referenced to GND. BIAS provides both click-and-pop suppression and sets the DC bias level for the amplifiers. Choose the value of the bypass capacitor as described in the BIAS Capacitor section. No external load should be applied to BIAS. Any load lowers the BIAS voltage, affecting the overall performance of the device. ______________________________________________________________________________________ 13 2.6W Stereo Audio Power Amplifiers and DirectDrive Headphone Amplifiers MAX9750/MAX9751/MAX9755 Table 1. MAX9750 Maximum Gain Settings GAIN1 0 0 1 1 GAIN2 0 1 0 1 SPEAKER MODE GAIN (dB) MAX9750A 9 12 10.5 13.5 MAX9750B 15 18 16.5 19.5 MAX9750C 6 9 7.5 10.5 HEADPHONE MODE GAIN (dB) 0 0 3 3 Table 2. MAX9751 Gain Settings GAIN 0 1 SPEAKER MODE GAIN (dB) 10.5 9 HEADPHONE MODE GAIN (dB) 3 0 VREF DAC VOL MAX9750 HPVDD BEEP Input The MAX9750 features an audible alert beep input (BEEP) that accepts a mono system alert signal and mixes it into the stereo audio path. When the amplitude of VBEEP(OUT) exceeds 800mVP-P (Figure 8) and the frequency of the beep signal is greater than 300Hz, the beep signal is mixed into the active audio path (speaker or headphone). If the signal at VBEEP(OUT) is either