MAX9768

19-0854; Rev 2; 11/08 KIT ATION EVALU ABLE AVAIL 10W Mono Class D Speaker Amplifier with Volume Control Features ♦ 10W Output (8Ω, PVDD = 14V, THD+N = 10%) ♦ Patented Spread-Spectrum Modulation ♦ Meets EN55022B EMC with Ferrite Bead Filters ♦ Amplifier Operation from 4.5V to 14V Supply ♦ 64-Step Integrated Volume Control (I2C or Analog) ♦ Low 0.08% THD+N (RL = 8Ω, POUT = 6W) ♦ High 77dB PSRR ♦ Two tON Times Offered MAX9768—220ms MAX9768B—15ms ♦ Low-Power Shutdown Mode (0.5µA) ♦ Short-Circuit and Thermal-Overload Protection General Description The MAX9768 mono 10W Class D speaker amplifier provides high-quality, efficient audio power with an integrated volume control function. The MAX9768 features a 64-step dual-mode (analog or digitally programmable) volume control and mute function. The audio amplifier operates from a 4.5V to 14V single supply and can deliver up to 10W into an 8Ω speaker with a 14V supply. A selectable spread-spectrum mode reduces EMI-radiated emissions, allowing the device to pass EMC testing with ferrite bead filters and cable lengths up to 1m. The MAX9768 can be synchronized to an external clock, allowing synchronization of multiple Class D amplifiers. The MAX9768 features high 77dB PSRR, low 0.08% THD+N, and SNR up to 97dB. Robust short-circuit and thermal-overload protection prevent device damage during a fault condition. The MAX9768 is available in a 24-pin thin QFN-EP (4mm x 4mm x 0.8mm) package and is specified over the extended -40°C to +85°C temperature range. MAX9768 Ordering Information PART MAX9768ETG+ MAX9768BETG+ PIN-PACKAGE 24 TQFN-EP* 24 TQFN-EP* tON (ms) 220 15 Applications Notebook Computers Flat-Panel Displays Multimedia Monitors GPS Navigation Systems Security/Personal Mobile Radio Note: All devices are specified over the -40°C to +85°C operating temperature range. +Denotes a lead-free/RoHS-compliant package. *EP = Exposed pad. Pin Configuration located at end of data sheet. Simplified Block Diagram 3.3V 4.5V TO 14V MAX9768 EMI WITH FERRITE BEAD FILTERS (VDD = 12V, 1m CABLE, 8Ω LOAD) 40 35 AMPLITUDE (dBμV/m) 30 25 20 15 10 5 OVER 20dB MARGIN TO EN55022B LIMIT SPEAKER AUDIO INPUT FILTERLESS CLASS D SPEAKER OUTPUT SHDN MUTE ANALOG OR I2C VOLUME CONTROL MAX9768 0 0 100 200 300 400 500 600 700 800 900 1000 FREQUENCY (MHz) ________________________________________________________________ Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 10W Mono Class D Speaker Amplifier with Volume Control MAX9768 ABSOLUTE MAXIMUM RATINGS PVDD to PGND........................................................-0.3V to +16V VDD to GND ..............................................................-0.3V to +4V SCLK, SDA/VOL to GND ..........................................-0.3V to +4V FB, SYNCOUT ............................................-0.3V to (VDD + 0.3V) BOOT_ to OUT_........................................................-0.3V to +4V OUT_ to GND ...........................................-0.3V to (PVDD + 0.3V) PGND to GND ......................................................-0.3V to +0.3V Any Other Pin to GND ..............................................-0.3V to +4V OUT_ Short-Circuit Duration.......................................Continuous Continuous Current (PVDD, PGND, OUT_) ..........................2.2A Continuous Input Current (Any Other Pin) .......................±20mA Continuous Input Current (FB_) .......................................±60mA Continuous Power Dissipation (TA = +70°C) Single-Layer Board: 24-Pin Thin QFN 4mm x 4mm, (derate 20.8mW/°C above +70°C) .................................1.67W Multilayer Board: 24-Pin Thin QFN 4mm x 4mm, (derate 27.8mW/°C above +70°C) .................................2.22W θJA, Single-Layer Board…...........................................….48°C/W θJA, Multilayer Board ...................................................….36°C/W 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 (VPVDD = 12V, VDD = 3.3V, VGND = VPGND = 0, V SHDN = VDD, VMUTE = 0; Max volume setting; speaker load resistor connected between OUT+ and OUT-, RL = ∞, unless otherwise noted. CBIAS = 2.2µF, C1 = C2 = 0.1µF, CIN = 0.47µF, RIN = 20kΩ, RF = 30kΩ, SSM mode. Filterless modulation mode (see the Functional Diagram/Typical Application Circuit). TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER GENERAL Speaker Supply Voltage Range Supply Voltage Range Quiescent Current Shutdown Current Output Offset Turn-On Time Common-Mode Bias Voltage Input Amplifier OutputVoltage Swing High Input Amplifier OutputVoltage Swing Low Input Amplifier Output Short-Circuit Current Limit Input Amplifier GainBandwidth Product SPEAKER AMPLIFIERS Internal Gain AVMAX Max volume setting; from FB to amplifier outputs |(OUT+) - (OUT-)|; excludes external gain resistors 29.27 30.1 31.00 dB GBW PVDD VDD IVDD IPVDD ISHDN VOS tON VBIAS VOH VOL Specified as VDD - VOH Specified as VOL - GND RL = 2kΩ connect to 1.5V RL = 2kΩ connect to 1.5V Filterless modulation Classic PWM modulation ISHDN = IPVDD + IDD, SHDN = GND, TA = +25°C Filterless modulation, VMUTE = VDD, TA = +25°C Filterless modulation, VMUTE = 0V, TA = +25°C MAX9768 MAX9768B Inferred from PSRR test Inferred from PSRR and UVLO test 4.5 2.7 7 4 4 0.5 ±2 ±2 220 15 1.5 3.6 6 ±60 1.8 100 50 14.0 3.6 14.2 7.6 7.6 50 ±12.5 ±14 µA mV ms V mV mV mA MHz mA V V SYMBOL CONDITIONS MIN TYP MAX UNITS 2 _______________________________________________________________________________________ 10W Mono Class D Speaker Amplifier with Volume Control ELECTRICAL CHARACTERISTICS (continued) (VPVDD = 12V, VDD = 3.3V, VGND = VPGND = 0, V SHDN = VDD, VMUTE = 0; Max volume setting; speaker load resistor connected between OUT+ and OUT-, RL = ∞, unless otherwise noted. CBIAS = 2.2µF, C1 = C2 = 0.1µF, CIN = 0.47µF, RIN = 20kΩ, RF = 30kΩ, SSM mode. Filterless modulation mode (see the Functional Diagram/Typical Application Circuit). TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER Efficiency (Note 2) SYMBOL η POUT = 8W, fIN = 1kHz, RL = 8Ω CONDITIONS Filterless modulation Classic PWM modulation RL = 8Ω, THD+N = 1%, filterless modulation PVDD = 5V RL = 8Ω, THD+N = 10%, filterless modulation RL = 8Ω, THD+N = 10%, classic PWM modulation Output Power (Note 2) POUT PVDD = 12V RL = 8Ω, THD+N = 10%, filterless modulation RL = 8Ω, THD+N = 10%, classic PWM modulation PVDD = 14V RL = 8Ω, THD+N = 10%, filterless modulation 1.75 f = 1kHz, RL = 8Ω, POUT = 5W 0dB = 8W, RL = 8Ω, BW = 22Hz to 22kHz, filterless modulation mode SNR 0dB = 8W, RL = 8Ω, BW = 22Hz to 22kHz, classic PWM modulation 0dB = 8W, f = 1kHz VDD = 2.7V to 3.6V, filterless modulation, TA = +25°C Power-Supply Rejection Ratio PSRR PVDD = 4.5V to 14V, filterless modulation, TA = +25°C f = 1kHz, VRIPPLE = 200mVP-P on PVDD f = 1kHz, VRIPPLE = 100mVP-P on VDD SYNC = GND Oscillator Frequency fOCS SYNC = unconnected SYNC = VDD (spread-spectrum modulation mode) 1060 1296 52 67 Unweighted A-weighted Filterless modulation Classic PWM modulation Unweighted A-weighted FFM SSM FFM SSM FFM SSM FFM SSM MIN TYP 87 85 1.3 1.7 9 W 9 10 10 2 2.5 0.09 0.08 94 93 97 97 93 89 97 91 115 68 84 77 60 1200 1440 1200 ±30 1320 1584 kHz dB dB dB A A % MAX UNITS % MAX9768 Soft Output Current Limit Hard Output Current Limit Total Harmonic Distortion Plus Noise (Note 2) ILIM ISC THD+N Signal-to-Noise Ratio (Note 2) MUTE Attenuation (Note 3) _______________________________________________________________________________________ 3 10W Mono Class D Speaker Amplifier with Volume Control MAX9768 ELECTRICAL CHARACTERISTICS (continued) (VPVDD = 12V, VDD = 3.3V, VGND = VPGND = 0, V SHDN = VDD, VMUTE = 0; Max volume setting; speaker load resistor connected between OUT+ and OUT-, RL = ∞, unless otherwise noted. CBIAS = 2.2µF, C1 = C2 = 0.1µF, CIN = 0.47µF, RIN = 20kΩ, RF = 30kΩ, SSM mode. Filterless modulation mode (see the Functional Diagram/Typical Application Circuit). TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER Class D Switching Frequency SYMBOL SYNC = GND SYNC = unconnected SYNC = VDD (spread-spectrum modulation mode) 1000 40 60 Full volume (ideal matching for RIN and RF) Peak voltage, 32 samples per second, A-weighted, RIN x CIN ≤ 10ms to guarantee clickless/popless operation Into shutdown Out of shutdown Into mute Out of mute 2 52.6 48 dBV 67 57 100 11 0.1 x VDD 0.9 x VDD 2.33 0.7 x VDD 0.8 0.3 x VDD ±7.5 ±13 ±1 VDD - 0.3 0.3 5 MΩ mV V V CONDITIONS MIN 265 324 TYP 300 360 300 ±7.5 1600 kHz % % % MAX 330 396 kHz UNITS SYNC Frequency Lock Range Minimum SYNC Frequency Lock Duty Cycle Maximum SYNC Frequency Lock Duty Cycle Gain Matching Click-and-Pop Level (Note 2) KCP Input Impedance Input Hysteresis 9.5dB Gain Voltage Full Mute Voltage DC volume control mode (SDA/VOL) DC volume control mode (SDA/VOL) DC volume control mode (SDA/VOL) DC volume control mode (SDA/VOL) SYNC All other pins SYNC All other pins TA = +25°C All other digital inputs, TA = +25°C Load = 1mA Load = 1mA CL = 10pF DIGITAL INPUTS (SHDN, MUTE, ADDR1, ADDR2, SYNC) Input-Voltage High Input-Voltage Low Input Leakage Current DIGITAL OUTPUT (SYNCOUT) Output-Voltage High Output-Voltage Low Rise/Fall Time V V ns VIH VIL ISYNC ILK V V µA 4 _______________________________________________________________________________________ 10W Mono Class D Speaker Amplifier with Volume Control ELECTRICAL CHARACTERISTICS (continued) (VPVDD = 12V, VDD = 3.3V, VGND = VPGND = 0, V SHDN = VDD, VMUTE = 0; Max volume setting; speaker load resistor connected between OUT+ and OUT-, RL = ∞, unless otherwise noted. CBIAS = 2.2µF, C1 = C2 = 0.1µF, CIN = 0.47µF, RIN = 20kΩ, RF = 30kΩ, SSM mode. Filterless modulation mode (see the Functional Diagram/Typical Application Circuit). TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER THERMAL PROTECTION Thermal Shutdown Threshold Thermal Shutdown Hysteresis DIGITAL INPUTS (SCLK, SDA/VOL) Input-Voltage High Input-Voltage Low Input High Leakage Current Input Low Leakage Current Input Hysteresis Input Capacitance DIGITAL OUTPUTS (SDA/VOL) Output High Current Output Low Voltage Serial Clock Bus Free Time Between a STOP and START Condition Hold Time (Repeated) START Condition Repeated START Condition Setup Time STOP Condition Setup Time Data Hold Time Data Setup Time SCL Clock Low Period SCL Clock High Period Rise Time of SDA and SCL, Receiving Fall Time of SDA and SCL, Receiving IOH VOL fSCL tBUF 1.3 VOH = VDD IOL = 3mA 1 0.4 400 µA V kHz µs CIN VIH VIL IIH IIL VIN = VDD, TA = +25°C VIN = GND, TA = +25°C 0.1 x VDD 5 0.7 x VDD 0.3 x VDD ±1 ±1 V V µA µA V pF 150 15 °C °C SYMBOL CONDITIONS MIN TYP MAX UNITS MAX9768 I2C TIMING CHARACTERISTICS (Figure 3) tHD,STA tSU,STA tSU,STO tHD,DAT tSU,DAT tLOW tHIGH tR tF (Note 4) (Note 4) 0.6 0.6 0.6 0 100 1.3 0.6 20 + 0.1Cb 20 + 0.1Cb 300 300 0.9 µs µs µs µs ns µs µs ns ns _______________________________________________________________________________________ 5 10W Mono Class D Speaker Amplifier with Volume Control MAX9768 ELECTRICAL CHARACTERISTICS (continued) (VPVDD = 12V, VDD = 3.3V, VGND = VPGND = 0, V SHDN = VDD, VMUTE = 0; Max volume setting; speaker load resistor connected between OUT+ and OUT-, RL = ∞, unless otherwise noted. CBIAS = 2.2µF, C1 = C2 = 0.1µF, CIN = 0.47µF, RIN = 20kΩ, RF = 30kΩ, SSM mode. Filterless modulation mode (see the Functional Diagram/Typical Application Circuit). TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER Fall Time of SDA, Transmitting Pulse Width of Spike Suppressed Capacitive Load for Each Bus Line SYMBOL tF tSP Cb (Note 4) CONDITIONS MIN 20 + 0.1Cb 0 TYP MAX 250 50 400 UNITS ns ns pF Note 1: All devices are 100% production tested at TA = +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 = 8Ω, L = 68µH. Note 3: Device muted by either asserting MUTE or minimum VOL setting. Note 4: Cb = total capacitance of one bus line in pF. Typical Operating Characteristics (VPVDD = 12V, VDD = 3.3V, VGND = VPGND = 0, VMUTE = 0; 0dB volume setting; all speaker load resistors connected between OUT+ and OUT-, RL = 8Ω, unless otherwise noted. CBIAS = 2.2µF, C1 = C2 = 0.1µF, CIN = 0.47µF, RIN = 20kΩ, RFB = 30kΩ, spread-spectrum modulation mode.) TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY MAX9768 toc01 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY MAX9768 toc02 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY PVDD = 5V RL = 8Ω FILTERLESS MODULATION 1 OUTPUT POWER = 1W 0.1 MAX9768 toc03 10 PVDD = 12V R L = 8Ω FILTERLESS MODULATION 1 THD+N (%) 10 PVDD = 12V RL = 8Ω PWM MODE 1 THD+N (%) 10 OUTPUT POWER = 6W 0.1 OUTPUT POWER = 5W 0.1 THD+N (%) 0.01 OUTPUT POWER = 2W 0.01 10 100 1k FREQUENCY (Hz) 10k 100k 0.01 10 100 1k FREQUENCY (Hz) 10k 100k OUTPUT POWER = 2W 0.001 10 OUTPUT POWER = 300mW 100 1k FREQUENCY (Hz) 10k 100k 6 _______________________________________________________________________________________ 10W Mono Class D Speaker Amplifier with Volume Control Typical Operating Characteristics (continued) (VPVDD = 12V, VDD = 3.3V, VGND = VPGND = 0, VMUTE = 0; 0dB volume setting; all speaker load resistors connected between OUT+ and OUT-, RL = 8Ω, unless otherwise noted. CBIAS = 2.2µF, C1 = C2 = 0.1µF, CIN = 0.47µF, RIN = 20kΩ, RFB = 30kΩ, spread-spectrum modulation mode.) TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY MAX9768 toc04 MAX9768 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY PVDD = 12V RL = 8Ω FILTERLESS MODULATION POUT = 4W FIXED-FREQUENCY MODULATION 0.1 MAX9768 toc05 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY PVDD = 12V RL = 8Ω PWM MODE POUT = 4W FIXED-FREQUENCY MODULATION MAX9768 toc06 10 PVDD = 5V R L = 8Ω PWM MODE 1 THD+N (%) 10 10 1 THD+N (%) 1 THD+N (%) 0.1 OUTPUT POWER = 300mW 0.1 0.01 OUTPUT POWER = 800mW 0.001 10 100 1k FREQUENCY (Hz) 10k 100k 0.01 SPREAD-SPECTRUM MODULATION 0.01 SPREAD-SPECTRUM MODULATION 0.001 10 100 1k FREQUENCY (Hz) 10k 100k 0.001 10 100 1k FREQUENCY (Hz) 10k 100k TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER MAX9768 toc07 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER MAX9768 toc08 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER PVDD = 5V RL = 8Ω FILTERLESS MODULATION fIN = 10kHz MAX9768 toc09 100 PVDD = 12V R L = 8Ω FILTERLESS MODULATION fIN = 10kHz 1 100 PVDD = 12V RL = 8Ω PWM MODE fIN = 10kHz 100 10 THD+N (%) 10 THD+N (%) 10 THD+N (%) 1 1 0.1 0.01 0.1 0.01 fIN = 100Hz 0.001 fIN = 1kHz 0.1 0.01 fIN = 100Hz fIN = 1kHz fIN = 100Hz fIN = 1kHz 0.001 0 2 4 6 8 10 12 OUTPUT POWER (W) 0.001 0 2 4 6 8 10 0 0.5 1.0 OUTPUT POWER (W) 1.5 2.0 OUTPUT POWER (W) TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER MAX9768 toc10 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER MAX9768 toc11 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER PVDD = 12V RL = 8Ω fIN = 1kHz PWM MODE MAX9768 toc12 100 PVDD = 5V R L = 8Ω PWM MODE fIN = 10kHz 100 PVDD = 12V RL = 8Ω fIN = 1kHz FILTERLESS MODULATION 100 10 THD+N (%) 10 THD+N (%) 10 THD+N (%) 1 1 0.1 0.01 fIN = 100Hz 0.001 0 0.4 0.8 1.2 1.6 2.0 OUTPUT POWER (W) fIN = 1kHz FIXED-FREQUENCY MODULATION 1 FIXED-FREQUENCY MODULATION 0.1 SPREAD-SPECTRUM MODULATION 0.01 0 2 4 6 8 10 OUTPUT POWER (W) 0.1 SPREAD-SPECTRUM MODULATION 0 2 4 6 8 10 0.01 OUTPUT POWER (W) _______________________________________________________________________________________ 7 10W Mono Class D Speaker Amplifier with Volume Control MAX9768 Typical Operating Characteristics (continued) (VPVDD = 12V, VDD = 3.3V, VGND = VPGND = 0, VMUTE = 0; 0dB volume setting; all speaker load resistors connected between OUT+ and OUT-, RL = 8Ω, unless otherwise noted. CBIAS = 2.2µF, C1 = C2 = 0.1µF, CIN = 0.47µF, RIN = 20kΩ, RFB = 30kΩ, spread-spectrum modulation mode.) EFFICIENCY vs. OUTPUT POWER MAX9768 toc13 EFFICIENCY vs. OUTPUT POWER FILTERLESS MODULATION PWM MODE MAX9768 toc14 EFFICIENCY vs. SUPPLY VOLTAGE fIN = 1kHz RL = 8Ω FILTERLESS MODULATION MAX9768 toc15 100 90 80 EFFICIENCY (%) 70 60 50 40 30 20 10 0 0 2 4 6 OUTPUT POWER (W) PVDD = 12V fIN = 1kHz RL = 8Ω 8 FILTERLESS MODULATION PWM MODE 100 90 80 EFFICIENCY (%) 70 60 50 40 30 20 10 0 95 92 EFFICIENCY (%) 89 THD+N = 10% 86 PVDD = 5V fIN = 1kHz RL = 8Ω 0 0.5 1.0 OUTPUT POWER (W) 1.5 2.0 83 THD+N = 1% 80 4.5 6.5 8.5 10.5 12.5 14.5 SUPPLY VOLTAGE (V) 10 EFFICIENCY vs. SUPPLY VOLTAGE MAX9768 toc16 OUTPUT POWER vs. SUPPLY VOLTAGE MAX9768 toc17 OUTPUT POWER vs. SUPPLY VOLTAGE RL = 4Ω fIN = 1kHz PWM MODE THD+N = 10% MAX9768 toc18 95 92 EFFICIENCY (%) fIN = 1kHz RL = 8Ω PWM MODULATION 14 12 OUTPUT POWER (W) 10 RL = 8Ω fIN = 1kHz PWM MODE THD+N = 10% 12 10 OUTPUT POWER (W) 8 6 4 2 0 89 THD+N = 10% 8 6 4 2 THD+N = 1% 86 THD+N = 1% 83 THD+N = 1% 80 4.5 6.5 8.5 10.5 12.5 14.5 SUPPLY VOLTAGE (V) 0 4 6 8 10 12 14 SUPPLY VOLTAGE (V) 4 6 8 10 12 14 SUPPLY VOLTAGE (V) OUTPUT POWER vs. LOAD RESISTANCE MAX9768 toc19 OUTPUT POWER vs. LOAD RESISTANCE MAX9768 toc20 CASE TEMPERATURE vs. OUTPUT POWER 80 CASE TEMPERATURE (°C) 70 60 50 40 30 20 PVDD = 12V fIN = 1kHz RL = 8Ω PVDD = 14V MAX9768 toc21 12 10 OUTPUT POWER (W) THD+N = 10% 8 6 4 THD+N = 1% 2 0 0 5 10 15 20 25 PVDD = 12V f = 1kHz PWM MODE 3.5 3.0 OUTPUT POWER (W) 2.5 2.0 1.5 1.0 0.5 0 THD+N = 1% THD+N = 10% PVDD = 5V f = 1kHz PWM MODE 90 10 0 0 5 10 15 20 25 30 0 2 4 6 8 10 12 LOAD RESISTANCE (Ω) OUTPUT POWER (W) 30 LOAD RESISTANCE (Ω) 8 _______________________________________________________________________________________ 10W Mono Class D Speaker Amplifier with Volume Control Typical Operating Characteristics (continued) (VPVDD = 12V, VDD = 3.3V, VGND = VPGND = 0, VMUTE = 0; 0dB volume setting; all speaker load resistors connected between OUT+ and OUT-, RL = 8Ω, unless otherwise noted. CBIAS = 2.2µF, C1 = C2 = 0.1µF, CIN = 0.47µF, RIN = 20kΩ, RFB = 30kΩ, spread-spectrum modulation mode.) POWER-SUPPLY REJECTION RATIO (PVDD) vs. FREQUENCY MAX9768 toc22 MAX9768 POWER-SUPPLY REJECTION RATIO (VDD) vs. FREQUENCY -10 -20 -30 PSRR (dB) -40 -50 -60 -70 -80 -90 FILTERLESS MODULATION PWM MODE VDD = 3.3V VRIPPLE = 100mVP-P RL = 8Ω MAX9768 toc23 OUTPUT WAVEFORM (FILTERLESS MODULATION) MAX9768 toc24 0 -10 -20 -30 PSRR (dB) -40 -50 -60 -70 -80 -90 -100 10 100 1k FREQUENCY (Hz) 10k FILTERLESS MODULATION PWM MODE PVDD = 12V VRIPPLE = 100mVP-P RL = 8Ω 0 5V/div 5V/div -100 10 100 1k FREQUENCY (Hz) 10k 100k 1μs/div 100k OUTPUT WAVEFORM (PWM MODE) MAX9768 toc25 OUTPUT FREQUENCY SPECTRUM MAX9768 toc26 OUTPUT FREQUENCY SPECTRUM VIN = -60dBV f = 1kHz RL = 8Ω UNWEIGHTED MAX9768 toc27 0 -20 OUTPUT MAGNITUDE (dBV) 5V/div -40 -60 -80 -100 -120 -140 OUTPUT MAGNITUDE (dBV) 20 FFM MODE VIN = -60dBV f = 1kHz RL = 8Ω UNWEIGHTED 0 -20 -40 -60 -80 -100 -120 -140 5V/div 1μs/div 0 5 10 FREQUENCY (kHz) 15 0 5 10 FREQUENCY (kHz) 15 20 WIDEBAND OUTPUT SPECTRUM (FIXED-FREQUENCY MODULATION MODE) MAX9768 toc28 WIDEBAND OUTPUT SPECTRUM (FIXED-FREQUENCY MODULATION MODE) MAX9768 toc29 WIDEBAND OUTPUT SPECTRUM (SPREAD-SPECTRUM MODULATION MODE) -10 OUTPUT AMPLITUDE (dBV) -20 -30 -40 -50 -60 -70 -80 -90 -100 RBW = 10kHz INPUT AC GROUNDED FILTERLESS MODULATION MAX9768 toc30 0 -10 OUTPUT AMPLITUDE (dBV) -20 -30 -40 -50 -60 -70 -80 -90 -100 1 10 0 -10 OUTPUT AMPLITUDE (dBV) -20 -30 -40 -50 -60 -70 -80 -90 -100 RBW = 10kHz INPUT AC GROUNDED FILTERLESS MODULATION RBW = 10kHz INPUT AC GROUNDED PWM MODE 0 100 1000 1 10 100 1000 1 10 100 1000 FREQUENCY (MHz) FREQUENCY (MHz) FREQUENCY (MHz) _______________________________________________________________________________________ 9 10W Mono Class D Speaker Amplifier with Volume Control MAX9768 Typical Operating Characteristics (continued) (VPVDD = 12V, VDD = 3.3V, VGND = VPGND = 0, VMUTE = 0; 0dB volume setting; all speaker load resistors connected between OUT+ and OUT-, RL = 8Ω, unless otherwise noted. CBIAS = 2.2µF, C1 = C2 = 0.1µF, CIN = 0.47µF, RIN = 20kΩ, RFB = 30kΩ, spread-spectrum modulation mode.) WIDEBAND OUTPUT SPECTRUM (SPREAD-SPECTRUM MODULATION MODE) -10 OUTPUT AMPLITUDE (dBV) -20 -30 -40 -50 -60 -70 -80 -90 -100 1 10 100 1000 100ms/div 40ms/div FREQUENCY (MHz) OUT 500mA/div OUT 500mA/div RBW = 10kHz INPUT AC GROUNDED PWM MODE MAX9768 toc31 TURN-ON/OFF RESPONSE (MAX9768) MAX9768 toc32 TURN-ON/OFF RESPONSE (MAX9768B) MAX9768 toc33 0 SHDN 2V/div SHDN 2V/div VOLUME CONTROL LEVEL vs. VOLUME CONTROL VOLTAGE MAX9768 toc34 SUPPLY CURRENT (PVDD) vs. SUPPLY VOLTAGE RL = ∞ 3.5 SUPPLY CURRENT (mA) 3.0 2.5 2.0 1.5 1.0 0.5 0 4 6 8 10 12 14 FILTERLESS MODULATION PWM MODE MAX9768 toc35 20 0 VOLUME LEVEL (dB) -20 -40 -60 -80 -100 -120 0 0.5 1.0 1.5 2.0 2.5 3.0 4.0 3.5 VVOL (V) SUPPLY VOLTAGE (V) SUPPLY CURRENT (VDD) vs. SUPPLY VOLTAGE MAX9768 toc36 SHUTDOWN CURRENT vs. SUPPLY VOLTAGE SHUTDOWN CURRENT = IPVDD + IDD VDD = 3.3V SHUTDOWN CURRENT (μA) 0.45 MAX9768 toc37 15 0.50 13 SUPPLY CURRENT (mA) PWM MODE 11 0.40 9 0.35 7 FILTERLESS MODULATION 5 2.6 2.8 3.0 3.2 3.4 3.6 SUPPLY VOLTAGE (V) 0.30 4 6 8 10 12 14 SUPPLY VOLTAGE (V) 10 ______________________________________________________________________________________ 10W Mono Class D Speaker Amplifier with Volume Control Pin Description PIN 1, 2 3, 16 4 NAME OUT+ PVDD BOOT+ Positive Speaker Output Speaker Amplifier Power-Supply Input. Bypass with a 1µF capacitor to ground. Positive Speaker Output Boost Flying-Capacitor Connection. Connect a 0.1µF ceramic capacitor between BOOT+ and OUT+. I2C Serial-Clock Input and Modulation Scheme Select. In I2C mode (ADDR1 and ADDR2 ≠ GND) acts as I2C serial-clock input. Connect SCLK to VDD for classic PWM modulation, or connect SCLK to ground for filterless modulation. I2C Serial Data I/O and Analog Volume Control Input Feedback. Connect feedback resistor between FB and IN to set amplifier gain. See the Adjustable Gain section. Audio Input Ground Common-Mode Bias Voltage. Bypass with a 2.2µF capacitor to GND. Frequency Select and External Clock Input. SYNC = GND: Fixed-frequency mode with fS = 300kHz. SYNC = Unconnected: Fixed-frequency mode with fS = 360kHz. SYNC = VDD: Spread-spectrum mode with fS = 300kHz ±7.5kHz. SYNC = Clocked: Fixed-frequency mode with fS = external clock frequency. Clock Signal Output Power-Supply Input. Bypass with a 1µF capacitor to GND. Negative Speaker Output Boost Flying-Capacitor Connection. Connect a 0.1µF ceramic capacitor between BOOTL- and OUTL-. Negative Speaker Output Shutdown Input. Drive SHDN low to disable the audio amplifiers. Connect SHDN to VDD for normal operation Mute Input. Drive MUTE high to mute the speaker outputs. Connect MUTE to GND for normal operation. Power Ground Address Select Input 2. I2C address option, also selects volume control mode. Address Select Input 1. I2C address option, also selects volume control mode. Exposed Pad. Connect the exposed thermal pad to GND, and use multiple vias to a solid copper area on the bottom of the PCB. FUNCTION MAX9768 5 6 7 8 9, 11 10 SCLK SDA/VOL FB IN GND BIAS 12 SYNC 13 14 15 17, 18 19 20 21, 22 23 24 — SYNCOUT VDD BOOTOUTSHDN MUTE PGND ADDR2 ADDR1 EP ______________________________________________________________________________________ 11 10W Mono Class D Speaker Amplifier with Volume Control MAX9768 Functional Diagram/Typical Application Circuit 2.7V to 3.6V 1μF VDD 14 RF 30kΩ FB 7 CIN RIN 0.47μF 20kΩ IN 8 VOLUME CONTROL MAX9768 4 BOOT+ 1, 2 OUT+ 17, 18 OUT15 BOOTMUTE 20 SHDN 19 SDA/VOL 6 SCLK 5 VDD ADDR1 24 ADDR2 23 SYNC 12 MUTE SHUTDOWN CONTROL I 2C ANALOG CONTROL OSCILLATOR 9, 11 GND 21, 22 PGND 13 SYNCOUT BIAS 10 BIAS CBIAS 2.2μF C2 0.1μF C1 0.1μF PVDD 3, 16 4.5V to 14V 1μ F (SHOWN IN ANALOG VOLUME CONTOL MODE, AV = 23.5dB, f-3dB = 17Hz, SPREAD-SPECTRUM MODULATION MODE, FILTERLESS MODULATION MODE, MUTE OFF) Detailed Description The MAX9768 10W, Class D audio power amplifier with spread-spectrum modulation provides a significant step forward in switch-mode amplifier technology. The MAX9768 offers Class AB performance with Class D efficiency and a minimal board space solution. This device features a wide supply voltage operation (4.5V to 14V), analog or digitally adjusted volume control, externally set input gain, shutdown mode, SYNC input and output, speaker mute, and industry-leading click-andpop suppression. The MAX9768 features a 64-step, dual-mode (analog or I2C programmed) volume control and mute function. In analog volume control mode, voltage applied to SDA/VOL sets the volume level. Two address inputs (ADDR1, ADDR2) set the volume control function between analog and I2C and set the slave address. In I2C mode there are three selectable slave addresses allowing for multiple devices on a single bus. Spread-spectrum modulation and synchronizable switching frequency significantly reduce EMI emissions. The outputs use Maxim’s low-EMI modulation scheme with minimum pulse outputs when the audio inputs are at the zero crossing. 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 topology reduces EMI and increases efficiency. 12 ______________________________________________________________________________________ CLASS D 10W Mono Class D Speaker Amplifier with Volume Control Operating Modes Fixed-Frequency Mode The MAX9768 features two fixed-frequency modes: 300kHz and 360kHz. Connect SYNC to GND to select 300kHz switching frequency; leave SYNC unconnected to select 360kHz switching frequency. The frequency spectrum of the MAX9768 consists of the fundamental switching frequency and its associated harmonics (see the Wideband Output Spectrum graphs in the Typical Operating Characteristics ). For applications where exact spectrum placement of the switching fundamental is important, 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. Spread-Spectrum Mode The MAX9768 features a unique, patented spreadspectrum mode that flattens the wideband spectral components, improving EMI emissions that may be radiated by the speaker and cables. This mode is enabled by setting SYNC = V DD (Table 1). In SSM mode, the switching frequency varies randomly by ±7.5kHz around the center frequency (300kHz). The modulation scheme remains the same, but the period of the triangle waveform changes from cycle to cycle. 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 input allows the MAX9768 to be synchronized to an external clock, or another Maxim Class D amplifier, creating a fully synchronous system, minimizing clock intermodulation, and allocating spectral components of the switching harmonics to insensitive frequency bands. Applying a clock signal between 1MHz and 1.6MHz to SYNC synchronizes the MAX9768. The Class D switching frequency is equal to one-fourth the SYNC input frequency. SYNCOUT is equal to the SYNC input frequency and allows several Maxim amplifiers to be cascaded. The synchronized output minimizes interference due to clock intermodulation caused by the switching spread between single devices. The modulation scheme remains the same when using SYNCOUT, and audio reproduction is not affected (Figure 1). Current flowing between SYNCOUT of a master device and SYNC of a slave device is low as the SYNC input is high impedance (typically 200kΩ). MAX9768 MAX9768 OUT+ OUT- SYNCOUT MAX9768 SYNC OUT+ OUT- Figure 1. Cascading Two Amplifiers Table 1. Operating Modes SYNC GND VDD Clocked OSCILLATOR FREQUENCY (kHz) Fixed-frequency modulation with fOSC = 1200 Spread-spectrum modulation with fOSC = 1200 ±30 Fixed-frequency modulation with fOSC = external clock frequency CLASS D FREQUENCY (kHz) Fixed-frequency modulation with fOSC = 300 Fixed-frequency modulation with fOSC = 360 Spread-spectrum modulation with fOSC = 300 ±7.5 Fixed-frequency modulation with fOSC = external clock frequency / 4 Unconnected Fixed-frequency modulation with fOSC = 1440 ______________________________________________________________________________________ 13 10W Mono Class D Speaker Amplifier with Volume Control Filterless Modulation/PWM Modulation The MAX9768 features two output modulation schemes: filterless modulation or classic PWM, selectable through SCLK when the device is in analog mode (ADDR2 and ADDR1 = GND, Table 2) or through the I2C interface (Table 7). Maxim’s unique, filterless modulation scheme eliminates the LC filter required by traditional Class D amplifiers, reducing component count, conserving board space and system cost. Although the MAX9768 meets FCC and other EMI limits with a lowcost ferrite bead filter, many applications still may want to use a full LC-filtered output. If using a full LC filter, the performance is best with the MAX9768 configured for classic PWM output. Switching between schemes while in normal operating mode with the I2C interface, the output is not click-andpop protected. To have click-and-pop protection when switching between output schemes, the device must enter shutdown mode and be configured to the new output scheme before the startup sequence is terminated. EFFICIENCY (%) MAX9768 Soft Current Limit When the output current exceeds the soft current limit, 2A (typ), the MAX9768 enters a cycle-by-cycle currentlimit mode. In soft current-limit mode, the output is clipped at 2A. When the output decreases so the output current falls below 2A, normal operation resumes. The effect of soft current limiting is a slight increase in distortion. Most applications will not enter soft currentlimit mode unless the speaker or filter creates impedance nulls below 8Ω. EFFICIENCY vs. OUTPUT POWER 90 80 70 60 50 40 30 20 10 0 0 2 4 6 8 10 OUTPUT POWER (W) PVDD = 12V fIN = 1kHz RL = 8Ω CLASS AB MAX9768 MAX9768 fig02 100 The startup time for the MAX9768 is typically 220ms. The startup time for the MAX9768B is typically 15ms. Efficiency Efficiency 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 current-steering 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 onresistance, and quiescent-current overhead. The theoretical best efficiency of a linear amplifier is 78%, however, that efficiency is only exhibited at peak output power. Under normal operating levels (typical music reproduction levels), efficiency falls below 30%, whereas the MAX9768 still exhibits > 80% efficiencies under the same conditions (Figure 2). Figure 2. MAX9768 Efficiency vs. Class AB Efficiency Table 2. Modulation Scheme Selection In Analog Mode ADDR2 0 0 ADDR1 0 0 SDA/VOL Analog Volume Control Analog Volume Control SCLK 0 1 FUNCTION Filterless Modulation Classic PWM (50% Duty Cycle) 14 ______________________________________________________________________________________ 10W Mono Class D Speaker Amplifier with Volume Control MAX9768 Hard Current Limit When the output current exceeds the hard current limit, 2.5A (typ), the MAX9768 disables the outputs and initiates a startup sequence. This startup sequence takes 220ms for the MAX9768 and 15ms for the MAX9768B. The shutdown and startup sequence is repeated until the output fault is removed. When in hard current limit, the output may make a soft clicking sound. The average supply current is relatively low, as the duty cycle of the output short is brief. Most applications will not enter hard current-limit mode unless the output is short circuited or incorrectly connected. MUTE should be held high during system power-up and power-down to ensure optimum click-and-pop performance. Volume Control The volume control operates from either an analog voltage input or through the I2C interface. The volume control has 64 levels, with the lowest setting equal to mute. To set the device to analog mode, connect ADDR1 and ADDR2 to GND. In analog mode, SDA/VOL is an analog input for volume control, see the F unctional Diagram/Typical Application Circuit. The analog input range is ratiometric between 0.9 x VDD and 0.1 x VDD, where 0.9 x VDD = full mute and 0.1 x VDD = full volume (Table 6). In I2C mode, volume control for the speaker is controlled separately by the command register (Tables 4, 5, 6). See the W rite Data Format s ection for more information regarding formatting data and tables to set volume levels. Thermal Shutdown When the die temperature exceeds the thermal shutdown threshold, +150°C (typ), the MAX9768 outputs are disabled. When the die temperature decreases below +135°C (typ), normal operation resumes. The effect of thermal shutdown is an output signal turning off for approximately 3s in most applications, depending on the thermal time constant of the audio system. Most applications should never enter thermal shutdown. Some of the possible causes of thermal shutdown are too low of a load impedance, high ambient temperature, poor PCB layout and assembly, or excessive output overdrive. I2C Interface The MAX9768 features an I2C 2-wire serial interface consisting of a serial data line (SDA) and a serial clock line (SCL). SDA and SCL facilitate communication between the MAX9768 and the master at clock rates up to 400kHz. When the MAX9768 is used on an I2C bus with multiple devices, the VDD supply must stay powered on to ensure proper I2C bus operation. The master, typically a microcontroller, generates SCL and initiates data transfer on the bus. Figure 3 shows the 2wire interface timing diagram. A master device communicates to the MAX9768 by transmitting the proper address followed by the data word. Each transmit sequence is framed by a START (S) or REPEATED START (Sr) condition and a STOP (P) condition. Each word transmitted over the bus is 8 bits long and is always followed by an acknowledge clock pulse. The MAX9768 SDA line operates as both an input and an open-drain output. A pullup resistor, greater than 500Ω, is required on the SDA bus. The MAX9768 SCL line operates as an input only. A pullup resistor, greater than 500Ω, is required on SCL if there are multiple masters on the bus, or if the master in a single-master system has an open-drain SCL output. Series resistors in line with SDA and SCL are optional. The SCL and SDA inputs suppress noise spikes to assure proper device operation even on a noisy bus. Shutdown The MAX9768 features a shutdown mode that reduces power consumption and extends battery life. Driving SHDN low places the device in low-power (0.5µA) shutdown mode. Connect SHDN to digital high for normal operation. In shutdown mode, the outputs are high impedance, SYNCOUT is pulled high, the BIAS voltage decays to zero, and the common-mode input voltage decays to zero. The I2C register retains its contents during shutdown. Undervoltage Lockout (UVLO) The MAX9768 features an undervoltage lockout protection that shuts down the device if either of the supplies are too low. The device will go into shutdown if VDD is less than 2.5V (VDD UVLO = 2.5V) or if PVDD is less than 4V (PVDD UVLO = 4V). Mute Function The MAX9768 features a clickless/popless mute mode. When the device is muted, the outputs do not stop switching, only the volume level is muted to the speaker. To mute the MAX9768, drive MUTE to logic-high. ______________________________________________________________________________________ 15 10W Mono Class D Speaker Amplifier with Volume Control MAX9768 SDA tSU,DAT tLOW SCL tHD,STA tR START CONDITION tHIGH tF REPEATED START CONDITION STOP CONDITION START CONDITION tHD,DAT tSU,STA tBUF tHD,STA tSP tSU,STO Figure 3. 2-Wire Serial-Interface Timing Diagram Bit Transfer One data bit is transferred during each SCL cycle. The data on SDA must remain stable during the high period of the SCL pulse. Changes in SDA while SCL is high are control signals (see the S TART and STOP Conditions section). SDA and SCL idle high when the I2C bus is not busy. START and STOP Conditions A master device initiates communication by issuing a START condition. A START condition is a high-to-low transition on SDA with SCL high. A STOP condition is a low-to-high transition on SDA while SCL is high (Figure 4). A START (S) condition from the master signals the beginning of a transmission to the MAX9768. The master terminates transmission, and frees the bus, by issuing a STOP (P) condition. The bus remains active if a REPEATED START (Sr) condition is generated instead of a STOP condition. Early STOP Conditions The MAX9768 recognizes a STOP condition at any point during data transmission except if the STOP condition occurs in the same high pulse as a START condition. Slave Address The slave address of the MAX9768 is 8 bits and consisting of 3 fields: the first field is 5 bits wide and is fixed (10010). The second is a 2-bit field, which is set through ADDR2 and ADDR1 (externally connected as logic-high or low). Third field is a R/W flag bit. Set R/W = 0 to write to the slave. A representation of the slave address is shown in Table 3. When ADDR1 and ADDR2 are connected to GND, serial interface communication is disabled. Table 4 summarizes the slave address of the device as a function of ADDR1 and ADDR2. Acknowledge The acknowledge bit (ACK) is a clocked 9th bit that the MAX9768 uses to handshake receipt each byte of data (Figure 5). The MAX9768 pulls down SDA during the master-generated 9th clock pulse. The SDA line must remain stable and low during the high period of the acknowledge clock pulse. Monitoring ACK allows for detection of unsuccessful data transfers. An unsuccessful data transfer occurs if a receiving device is busy or if a system fault has occurred. In the event of an unsuccessful data transfer, the bus master can reattempt communication. S Sr P SCL SDA Figure 4. START, STOP, and REPEATED START Conditions 16 ______________________________________________________________________________________ 10W Mono Class D Speaker Amplifier with Volume Control Table 3. Slave Address Block SA7 (MSB) 1 SA6 0 SA5 0 SA4 1 SA3 0 SA2 ADDR2 SA1 ADDR1 SA0 (LSB) R/W MAX9768 Table 4. Slave Address ADDR2 0 0 1 1 ADDR1 0 1 0 1 SLAVE ADDRESS Disabled 1001001_ 1001010_ 1001011_ SDA ACKNOWLEDGE START CONDITION SCL 1 2 CLOCK PULSE FOR ACKNOWLEDGMENT 8 NOT ACKNOWLEDGE 9 Write Data Format A write to the MAX9768 includes transmission of a START condition, the slave address with the R/W bit set to 0 (see Table 3), one byte of data to the command register, and a STOP condition. Figure 6 illustrates the proper format for one frame. Volume Control The command register is used to control the volume level of the speaker amplifier. The two MSBs (D7 and D6) should be set to 00 to choose the speaker register. V5–V0 is the volume control data that will be written into the addresses register to set the volume level (see Tables 5 and 6). For a write byte operation, the master sends a single byte to the slave device (MAX9768). This is done as follows: 1) The master sends a start condition. 2) The master sends the 7-bit slave ID plus a write bit (low). 3) The addressed slave asserts an ACK on the data line. 4) The master sends 8 data bits. 5) The active slave asserts an ACK (or NACK) on the data line. 6) The master generates a stop condition. Figure 5. Acknowledge WRITE BYTE FORMAT S SLAVE ADDRESS 7 bits SLAVE ADDRESS: EQUIVALENT TO CHIPSELECT LINE OF A 3WIRE INTERFACE. WR 0 ACK DATA 8 bits DATA BYTE: GIVES A COMMAND. ACK P Figure 6. Write Data Format Example ______________________________________________________________________________________ 17 10W Mono Class D Speaker Amplifier with Volume Control MAX9768 Table 5. Data Byte Format D7 (MSB) 0 D6 0 D5 V5 D4 V4 D3 V3 D2 V2 D1 V1 D0 (LSB) V0 Table 6. Speaker Volume Levels V5 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 V4 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 V3 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 V2 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 V1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 V0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 VOLUME POSITION 63 62 61 60 59 58 57 56 55 54 53 52 51 50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32 VOLUME LEVEL (dB) 9.5 8.8 8.2 7.6 7.0 6.5 5.9 5.4 4.9 4.4 3.9 3.4 2.9 2.4 2.0 1.6 1.2 0.5 -0.5 -1.9 -3.4 -5.0 -6.0 -7.1 -8.9 -9.9 -10.9 -12.0 -13.1 -14.4 -15.4 -16.4 STEP SIZE (dB) 0.7 0.7 0.6 0.6 0.6 0.5 0.5 0.5 0.5 0.5 0.6 0.4 0.5 0.4 0.4 0.4 0.7 1.0 1.5 1.5 1.5 1.1 1.1 1.8 1.0 1.0 1.1 1.2 1.3 0.9 1.0 1.1 18 ______________________________________________________________________________________ 10W Mono Class D Speaker Amplifier with Volume Control Table 6. Speaker Volume Levels (continued) V5 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 V4 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 V3 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 V2 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 V1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 V0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 VOLUME POSITION 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 (MUTE) VOLUME LEVEL (dB) -17.5 -19.7 -21.6 -23.5 -25.2 -27.2 -29.8 -31.5 -33.4 -36.0 -37.6 -39.6 -42.1 -43.7 -45.6 -48.1 -50.6 -54.2 -56.7 -60.2 -62.7 -66.2 -68.7 -72.2 -74.7 -78.3 -80.8 -84.3 -86.8 -90.3 -92.8 -161.5 STEP SIZE (dB) 2.2 1.9 1.9 1.7 2.0 2.6 1.6 2.0 2.5 1.6 2.0 2.5 1.6 2.0 2.5 2.5 3.5 2.5 3.5 2.5 3.5 2.5 3.5 2.5 3.5 2.5 3.5 2.5 3.5 2.5 — — MAX9768 19 ______________________________________________________________________________________ 10W Mono Class D Speaker Amplifier with Volume Control MAX9768 Applications Information Filterless Class D Operation The MAX9768 can be operated without a filter and meet common EMC radiation limits when the speaker leads are less than approximately 10cm. Lengths beyond 10cm are possible but should be verified against the appropriate EMC standard. Select the filterless modulation mode with spread-spectrum modulation mode for best performance. For longer speaker wire lengths, a simple ferrite bead and capacitor-based filter can be used to meet EMC limits. See Figure 7 for the correct connections of these components. Select a ferrite bead with 100Ω to 600Ω impedance, and rated for at least 1.5A. The capacitor value will vary based on the ferrite bead chosen and the actual speaker lead length. Select the capacitor value based on EMC performance. When doing bench evaluation without a filter or a ferrite bead filter, include a series inductor (68µH for 8Ω load) to model the actual loudspeaker’s behavior. If this inductance is omitted, the MAX9768 will have reduced efficiency and output power, as well as worse THD+N performance. Table 7. Setting Class D Output Modulation Scheme D7 (MSB) 1 1 D6 1 1 D5 0 0 D4 1 1 D3 0 0 D2 1 1 D1 0 1 D0 (LSB) 1 0 Classic PWM FILTERLESS MODULATION* FUNCTION *Power-on default. BOOT_+ C1 0.1μF OUT_+ MAX9768 C9 330pF OUT_C2 0.1μF C10 330pF BOOT_- Figure 7. Ferrite Bead Filter 20 ______________________________________________________________________________________ 10W Mono Class D Speaker Amplifier with Volume Control Inductor-Based Output Filters Some applications will use the MAX9768 with a full inductor-/capacitor-based (LC) output filter. This is common for longer speaker lead lengths, and to gain increased margin to EMC limits. Select the PWM output mode and use fixed-frequency modulation mode for best audio performance. See Figure 8 for the correct connections of these components. The component selection is based on the load impedance of the speaker. Table 8 lists suggested values for a variety of load impedances. Inductors L3 and L4, and capacitor C15 form the primary output filter. In addition to these primary filter components, other components in the filter improve its functionality. Capacitors C13 and C14, plus resistors R6 and R7, form a Zobel at the output. A Zobel corrects the output loading to compensate for the rising impedance of the loudspeaker. Without a Zobel, the filter will have a peak in its response near the cutoff frequency. Capacitors C11 and C12 provide additional high-frequency bypass to reduce radiated emissions. Adjustable Gain Gain-Setting Resistors External feedback resistors set the gain of the MAX9768. The output stage has an internal 20dB gain in addition to the externally set gain. Set the maximum gain by using resistors RF and RIN (Figure 9) as follows: ⎛R ⎞ AV = − 10⎜ F ⎟ V / V ⎝ RIN ⎠ Choose RF between 10kΩ and 50kΩ. Please note that the actual gain of the amplifier is dependent on the volume level setting. For example, with the volume control set to +9.5dB, the amplifier gain would be 9.5dB + 20dB, assuming RF = RIN. The input amplifier can be configured into a variety of circuits. The FB terminal is an actual operational amplifier output, allowing the MAX9768 to be configured as a summing amplifier, a filter, or an equalizer, for example. MAX9768 4 BOOT_+ C1 0.1μF L4 C11 C13 C15 1, 2 MAX9768 OUT_+ R6 RL 14, 18 OUT_C2 0.1μF L3 C12 C14 R7 15 BOOT_- Figure 8. Output Filter for PWM Mode Table 8. Suggested Values for LC filter RL (Ω) 6 8 12 L3, L4 (µH) 15 22 33 C15 (µF) 0.33 0.22 0.1 C11, C12 (µF) 0.01 0.01 0.01 R6, R7 (Ω) 7.5 10 15 C13, C14 (µF) 0.68 0.47 0.33 ______________________________________________________________________________________ 21 10W Mono Class D Speaker Amplifier with Volume Control MAX9768 12V BOOT+ AUDIO CIN INPUT RIN IN MAX9768 IN OUT+ 1μF SHDN PVDD OUT 3.3V VDD MAX9768 1μF RF FB OUT- MAX1726 BOOT- GND GND Figure 9. Setting Gain Figure 10. Using a Linear Regulator to Produce 3.3V from a 12V Power Supply Power Supplies The MAX9768 has different supplies for each portion of the device, allowing for the optimum combination of headroom power dissipation and noise immunity. The speaker amplifiers are powered from PVDD and can range from 4.5V to 14V. The remainder of the device is powered by VDD. Power supplies are independent of each other so sequencing is not necessary. Power may be supplied by separate sources or derived from a single higher source using a linear regulator to reduce the voltage as shown in Figure 10. on the frequency range of the spoken human voice (typically 300Hz to 3.5kHz). In addition, speakers used in portable devices typically have a poor response below 300Hz. Taking these two factors into consideration, the input filter may not need to be designed for a 20Hz to 20kHz response, saving both board space and cost due to the use of smaller capacitors. Component Selection Input Filter An input capacitor, CIN, in conjunction with the input resistor of the MAX9768 forms a highpass filter that removes the DC bias from an incoming signal. The ACcoupling 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 − 3 dB = 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. Bypass BIAS with a 2.2µF capacitor to GND. Supply Bypassing, Layout, and Grounding Proper layout and grounding are essential for optimum performance. Use large traces for the power-supply inputs and amplifier outputs to minimize losses due to parasitic trace resistance. Large traces also aid in moving heat away from the package. Proper grounding improves audio performance, minimizes crosstalk between channels, and prevents any switching noise from coupling into the audio signal. Connect PGND and GND together at a single point on the PCB. Route all traces that carry switching transients away from GND and the traces/components in the audio signal path. Bypass VDD and PVDD with a 1µF capacitor to PGND. Place the bypass capacitors as close to the MAX9768 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 MAX9768 to the air, decreasing the thermal impedance of the circuit if possible. 1 2πRINCIN Choose CIN so f-3dB is well below the lowest frequency of interest. Use capacitors whose dielectrics have lowvoltage coefficients, such as tantalum or aluminum electrolytic. Capacitors with high-voltage coefficients, such as ceramics, may result in increased distortion at low frequencies. Other considerations when designing the input filter include the constraints of the overall system and the actual frequency band of interest. Although high-fidelity audio calls for a flat-gain response between 20Hz and 20kHz, portable voice-reproduction devices such as cellular phones and two-way radios need only concentrate 22 ______________________________________________________________________________________ 10W Mono Class D Speaker Amplifier with Volume Control Pin Configuration PROCESS: BICMOS TOP VIEW BOOTOUTPVDD OUTVDD SYNCOUT Chip Information MAX9768 18 SHDN 19 MUTE 20 PGND 21 PGND 22 ADDR2 23 + ADDR1 24 1 OUT+ 17 16 15 14 13 12 SYNC 11 GND 10 BIAS MAX9768 9 8 7 GND IN FB 2 OUT+ 3 PVDD 4 BOOT+ 5 SCLK 6 SDA/VOL TQFN (4mm × 4mm) ______________________________________________________________________________________ 23 10W Mono Class D Speaker Amplifier with Volume Control MAX9768 Package Information For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. PACKAGE TYPE 24 TQFN-EP PACKAGE CODE T2444+4 DOCUMENT NO. 21-0139 24 ______________________________________________________________________________________ 24L QFN THIN.EPS 10W Mono Class D Speaker Amplifier with Volume Control Package Information (continued) For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. MAX9768 ______________________________________________________________________________________ 25 10W Mono Class D Speaker Amplifier with Volume Control MAX9768 Revision History REVISION NUMBER 0 1 2 REVISION DATE 9/07 3/08 11/08 Initial release Updated package outline Corrected various items DESCRIPTION PAGES CHANGED — 24, 25 2, 4, 5, 11 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. 26 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2008 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc. Heaney