MAX9703/MAX9704 10W Stereo/15W Mono, Filterless, Spread-Spectrum, Class D Amplifiers General Description The MAX9703/MAX9704 mono/stereo Class D audio power amplifiers provide Class AB amplifier performance with Class D efficiency, conserving board space and eliminating the need for a bulky heatsink. Using a Class D architecture, these devices deliver up to 15W while offering up to 78% efficiency. Proprietary and protected modulation and switching schemes render the traditional Class D output filter unnecessary. The MAX9703/MAX9704 offer two modulation schemes: a fixed-frequency mode (FFM), and a spread-spectrum mode (SSM) that reduces EMI-radiated emissions due to the modulation frequency. The device utilizes a fully differential architecture, a full bridged output, and comprehensive click-and-pop suppression. The MAX9703/MAX9704 feature high 80dB PSRR, low 0.07% THD+N, and SNR in excess of 95dB. Short-circuit and thermal-overload protection prevent the devices from being damaged during a fault condition. The MAX9703 is available in a 32-pin TQFN (5mm x 5mm x 0.8mm) package. The MAX9704 is available in a 32-pin TQFN (7mm x 7mm x 0.8mm) package. Both devices are specified over the extended -40C to +85C temperature range. Applications LCD TVs LCD Monitors Desktop PCs LCD Projectors Hands-Free Car Phone Adapters Block Diagrams Features Filterless Class D Amplifier Unique Spread-Spectrum Mode Offers 5dB Emissions Improvement Over Conventional Methods Up to 78% Efficient (RL = 8) Up to 88% Efficient (RL = 16) 15W Continuous Output Power into 8 (MAX9703) 2x10W Continuous Output Power into 8 (MAX9704) Low 0.07% THD+N High PSRR (80dB at 1kHz) 10V to 25V Single-Supply Operation Differential Inputs Minimize Common-Mode Noise Pin-Selectable Gain Reduces Component Count Industry-Leading Click-and-Pop Suppression Low Quiescent Current (24mA) Low-Power Shutdown Mode (0.2A) Short-Circuit and Thermal-Overload Protection Available in Thermally Efficient, Space-Saving Packages * 32-Pin TQFN (5mm x 5mm x 0.8mm)-MAX9703 * 32-Pin TQFN (7mm x 7mm x 0.8mm)-MAX9704 Ordering Information PART MAX9703ETJ+ 0.47F 0.47F IN+ IN- 0.47F OUT- 0.47F 19-3160; Rev 8; 5/14 T3255-4 MAX9704 INL- H-BRIDGE INR+ 0.47F Pin Configurations appears at end of data sheet. PKG CODE Mono INL+ OUT+ H-BRIDGE AMP 32 TQFN-EP* MAX9704ETJ+ 32 TQFN-EP* Stereo T3277-2 Note: All devices specified for over -40C to +85C operating temperature range. *EP = Exposed paddle. +Denotes lead-free package. 0.47F MAX9703 PIN-PACKAGE INR- OUTL+ OUTL- OUTR+ H-BRIDGE OUTR- MAX9703/MAX9704 10W Stereo/15W Mono, Filterless, Spread-Spectrum, Class D Amplifiers Absolute Maximum Ratings (All voltages referenced to PGND.) VDD to PGND, AGND............................................................30V OUTR_, OUTL_, C1N.................................-0.3V to (VDD + 0.3V) C1P............................................(VDD - 0.3V) to (CHOLD + 0.3V) CHOLD........................................................(VDD - 0.3V) to +40V All Other Pins to PGND...........................................-0.3V to +12V Duration of OUTR_/OUTL_ Short Circuit to PGND, VDD................................................10s Continuous Input Current (VDD, PGND) ...............................1.6A Continuous Input Current......................................................0.8A Continuous Input Current (all other pins)..........................20mA Continuous Power Dissipation (TA = +70C) Single-Layer Board: MAX9703 32-Pin TQFN (derate 21.3mW/C above +70C)..........................................................1702.1mW MAX9704 32-Pin TQFN (derate 27mW/C above +70C)..........................................................2162.2mW Multilayer Board: MAX9703 32-Pin TQFN (derate 34.5mW/C above +70C)..........................................................2758.6mW MAX9704 32-Pin TQFN (derate 37mW/C above +70C)..........................................................2963.0mW Junction Temperature......................................................+150C Operating Temperature Range ...........................-40C to +85C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C 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 = 15V, AGND = PGND = 0V, SHDN VIH, AV = 16dB, CSS = CIN = 0.47F, CREG = 0.01F, C1 = 100nF, C2 = 1F, FS1 = FS2 = PGND (fS = 660kHz), RL connected between OUTL+ and OUTL- and OUTR+ and OUTR-, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) (Notes 1, 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 25 V GENERAL Supply Voltage Range VDD Inferred from PSRR test Quiescent Current IDD RL = OPEN Shutdown Current ISHDN Turn-On Time tON Amplifier Output Resistance in Shutdown Input Impedance RIN 10 MAX9703 14 22 MAX9704 24 34 0.2 1.5 CSS = 470nF 100 CSS = 180nF SHDN = PGND 150 330 AV = 13dB 35 58 80 30 48 65 AV = 19.1dB 23 39 55 AV = 29.6dB Voltage Gain AV Gain Matching Output Offset Voltage Common-Mode Rejection Ratio Power-Supply Rejection Ratio (Note 3) www.maximintegrated.com VOS CMRR 10 15 22 29.4 29.6 29.8 G1 = L, G2 = H 18.9 19.1 19.3 G1 = H, G2 = L 12.8 13 13.2 G1 = H, G2 = H 15.9 16 16.3 0.5 fIN = 1kHz, input referred 60 6 VDD = 10V to 25V PSRR k G1 = L, G2 = L Between channels (MAX9704) 200mVP-P ripple 54 A ms 50 AV = 16dB mA k dB % 30 mV dB 80 fRIPPLE = 1kHz 80 fRIPPLE = 20kHz 66 dB Maxim Integrated 2 MAX9703/MAX9704 10W Stereo/15W Mono, Filterless, Spread-Spectrum, Class D Amplifiers Electrical Characteristics (continued) (VDD = 15V, AGND = PGND = 0V, SHDN VIH, AV = 16dB, CSS = CIN = 0.47F, CREG = 0.01F, C1 = 100nF, C2 = 1F, FS1 = FS2 = PGND (fS = 660kHz), RL connected between OUTL+ and OUTL- and OUTR+ and OUTR-, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) (Notes 1, 2) PARAMETER Continuous Output Power (MAX9703) Continuous Output Power (MAX9704) Total Harmonic Distortion Plus Noise SYMBOL PCONT PCONT THD+N Signal-to-Noise Ratio SNR Crosstalk CONDITIONS THD+N = 10%, VDD = 16V, f = 1kHz, TA = +25C, tCONT = 15min (Note 4) THD+N = 10%, VDD = 16V, f = 1kHz, TA = +25C, tCONT = 15min (Note 4) MIN 10 RL = 8 15 RL = 16, VDD = 24V 18 RL = 4 2x5 RL = 8 2x10 RL = 16, VDD = 24V 2x16 BW = 22Hz to 22kHz A-weighted 94 SSM 88 FFM 97 SSM 91 Left to right, right to left, 8 load, fIN = 10kHz Efficiency Regulator Output fOSC W % dB 65 560 670 FS1 = L, FS2 = H 940 FS1 = H, FS2 = L 470 FS1 = H, FS2 = H (spread-spectrum mode) 670 7% POUT = 15W, f = 1kHz, RL = 8 78 POUT = 10W, f = 1kHz, RL = 16 88 VREG UNITS W 0.07 FFM FS1 = L, FS2 = L Oscillator Frequency MAX RL = 4 fIN = 1kHz, either FFM or SSM, RL = 8, POUT = 4W RL = 8, POUT = 10W, f = 1kHz TYP dB 800 kHz % 6 V DIGITAL INPUTS (SHDN, FS_, G_) Input Thresholds Input Leakage Current VIH VIL 2.5 0.8 1 V A Note 1: All devices are 100% production tested at +25C. All temperature limits are guaranteed by design. Note 2: Testing performed with a resistive load in series with an inductor to simulate an actual speaker load. For RL = 8, L = 68H. For RL = 4, L = 33H. Note 3: PSRR is specified with the amplifier inputs connected to AGND through CIN. Note 4: The MAX9704 continuous 8 and 16 power measurements account for thermal limitations of the 32-pin TQFN-EP package. Continuous 4 power measurements account for short-circuit protection of the MAX9703/MAX9704 devices. www.maximintegrated.com Maxim Integrated 3 MAX9703/MAX9704 10W Stereo/15W Mono, Filterless, Spread-Spectrum, Class D Amplifiers Typical Operating Characteristics (33H with 4, 68H with 8, part in SSM mode, 136H with 16, measurement BW = 22Hz to 22kHz, unless otherwise noted.) POUT = 4W 0.1 1 POUT = 8W POUT = 8W 0.1 100 1k POUT = 500mW POUT = 500mW 10k 0.01 100k 10 100 1k 10k 0.01 100k 10 100 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER VDD = 15V RL = 8 AV = 16dB f = 10kHz 1 THD+N (%) SSM VDD = 15V RL = 4 AV = 16dB 10 10 MAX9703/04 toc05 100 MAX9703/04 toc04 VDD = 20V RL = 8 AV = 16dB POUT = 8W f = 10kHz 1 f = 1kHz 0.1 f = 1kHz f = 100Hz 10 100 1k 10k 0.01 100k 0 1 2 3 4 5 6 7 8 9 OUTPUT POWER (W) TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER f = 10kHz 1 THD+N (%) 1 f = 1kHz VDD = 20V RL = 8 AV = 16dB f = 1kHz SSM 0.1 0.1 FFM (335kHz) f = 100Hz 0 2 4 6 EFFICIENCY vs. OUTPUT POWER 100 RL = 8 90 80 EFFICIENCY (%) 10 MAX9703/04 toc07 VDD = 20V RL = 8 AV = 16dB 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 OUTPUT POWER (W) MAX9703/04 toc08 FREQUENCY (Hz) 10 0.01 10 MAX9703/04 toc09 0.1 f = 100Hz THD+N (%) MAX9703/04 toc06 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY FFM 0.01 100k FREQUENCY (Hz) 0.1 100 10k FREQUENCY (Hz) 1 0.01 1k FREQUENCY (Hz) THD+N (%) THD+N (%) 10 10 VDD = 20V RL = 8 AV = 16dB 1 0.1 POUT = 500mW 0.01 10 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY MAX9703/04 toc03 VDD = 15V RL = 8 AV = 16dB THD+N (%) 1 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY MAX9703/04 toc02 10 MAX9703/04 toc01 VDD = 15V RL = 4 AV = 16dB THD+N (%) THD+N (%) 10 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY 70 60 50 RL = 4 40 30 20 VDD = 12V AV = 16dB f = 1kHz 10 8 10 12 14 16 18 OUTPUT POWER (W) www.maximintegrated.com 20 0.01 0 1 2 3 4 5 6 7 8 9 10111213141516171819 20 OUTPUT POWER (W) 0 0 1 2 3 4 5 6 7 8 9 10 OUTPUT POWER (W) Maxim Integrated 4 MAX9703/MAX9704 10W Stereo/15W Mono, Filterless, Spread-Spectrum, Class D Amplifiers Typical Operating Characteristics (continued) (33H with 4, 68H with 8, part in SSM mode, 136H with 16, measurement BW = 22Hz to 22kHz, unless otherwise noted.) 30 VDD = 15V AV = 16dB f = 1kHz 10 0 2 6 4 8 10 12 14 16 18 RL = 8 12 RL = 16 10 8 6 4 0 10 13 OUTPUT POWER (W) VDD = 15V RL = 8 AV = 16dB -10 -20 10 -40 -50 -80 100 MAX9703/04 toc16 AV = 16dB 1% THD+N VDD = 15V 8 LOAD -40 LEFT TO RIGHT -60 -80 -120 RIGHT TO LEFT 100 1k FREQUENCY (Hz) www.maximintegrated.com MAX9703/04 toc12 100 POWER-SUPPLY REJECTION RATIO vs. FREQUENCY AV = 16dB RL = 8 200mVP-P INPUT VDD = 15V -20 -60 -80 -100 100 10 1k 10k 10k -120 100k 100 10 OUTPUT FREQUENCY SPECTRUM 20 FFM MODE AV = 16dB UNWEIGHTED fIN = 1kHz POUT = 5W RL = 8 0 -20 -40 100k -60 -80 -100 -140 1k 10k 100k FREQUENCY (Hz) -120 10 10 FREQUENCY (Hz) CROSSTALK vs. FREQUENCY -100 1 0 -70 OUTPUT MAGNITUDE (dB) CROSSTALK (dB) -20 THD+N = 1% -40 -30 LOAD RESISTANCE () 0 6 -60 THD+N = 1% 1 8 LOAD RESISTANCE () COMMON-MODE REJECTION RATIO vs. FREQUENCY 0 10 0 25 PSRR (dB) THD+N = 10% 12 2 OUTPUT FREQUENCY SPECTRUM 20 SSM MODE AV = 16dB UNWEIGHTED fIN = 1kHz POUT = 5W RL = 8 0 OUTPUT MAGNITUDE (dB) 0 VDD = 20V AV = 16dB MAX9703/04 toc13 24 22 20 18 16 14 12 10 8 6 4 2 CMRR (dB) OUTPUT POWER (W) OUTPUT POWER vs. LOAD RESISTANCE 16 19 22 SUPPLY VOLTAGE (V) THD+N = 10% 14 4 AV = 16dB THD+N = 10% 2 20 16 -20 -40 MAX9703/04 toc18 20 14 VDD = 15V AV = 16dB 18 MAX9703/04 toc15 40 20 OUTPUT POWER (W) RL = 8 50 0 16 MAX9703/04 toc17 EFFICIENCY (%) 70 60 18 OUTPUT POWER (W) 80 OUTPUT POWER vs. LOAD RESISTANCE MAX9703/04 toc11 RL = 16 90 20 MAX9703/04 toc10 100 OUTPUT POWER vs. SUPPLY VOLTAGE MAX9703/04 toc14 EFFICIENCY vs. OUTPUT POWER -60 -80 -100 -120 0 2 4 6 8 10 12 14 16 18 20 FREQUENCY (kHz) -140 0 2 4 6 8 10 12 14 16 18 20 FREQUENCY (kHz) Maxim Integrated 5 MAX9703/MAX9704 10W Stereo/15W Mono, Filterless, Spread-Spectrum, Class D Amplifiers Typical Operating Characteristics (continued) (33H with 4, 68H with 8, part in SSM mode, 136H with 16, measurement BW = 22Hz to 22kHz, unless otherwise noted.) -60 -80 -100 -40 -60 -80 2 4 -120 6 8 10 12 14 16 18 20 FREQUENCY (kHz) TURN-ON/TURN-OFF RESPONSE MAX9703/04 toc22 100k 35 CSS = 180pF 1M 10M 1V/div OUTPUT SUPPLY CURRENT (mA) 5V/div 20ms/div 1M 10M 100M SUPPLY CURRENT vs. SUPPLY VOLTAGE SHUTDOWN CURRENT vs. SUPPLY VOLTAGE 25 20 15 10 0 100k FREQUENCY (Hz) 0.35 0.30 0.25 0.20 0.15 0.10 0.05 10 13 16 19 SUPPLY VOLTAGE (V) www.maximintegrated.com -80 FREQUENCY (Hz) 5 f = 1kHz RL = 8 -60 -120 100M 30 SHDN -40 -100 SHUTDOWN CURRENT (A) 0 RBW = 10kHz VDD = 15V -20 MAX9703/04 toc21 0 -100 -120 -140 -20 WIDEBAND OUTPUT SPECTRUM (SSM MODE) MAX97703/04 toc24 -40 RBW = 10kHz VDD = 15V MAX9703/04 toc20 -20 0 MAX9703/04 toc23 OUTPUT MAGNITUDE (dB) 0 WIDEBAND OUTPUT SPECTRUM (FFM MODE) OUTPUT AMPLITUDE (dBV) SSM MODE AV = 16dB A-WEIGHTED fIN = 1kHz POUT = 5W RL = 8 OUTPUT AMPLITUDE (dBV) 20 MAX9703/04 toc19 OUTPUT FREQUENCY SPECTRUM 22 25 0 10 12 14 16 18 20 SUPPLY VOLTAGE (V) Maxim Integrated 6 MAX9703/MAX9704 10W Stereo/15W Mono, Filterless, Spread-Spectrum, Class D Amplifiers Pin Description PIN NAME FUNCTION MAX9703 MAX9704 1, 2, 23, 24 1, 2, 23, 24 3, 4, 21, 22 3, 4, 21, 22 VDD Power-Supply Input 5 5 C1N Charge-Pump Flying Capacitor Negative Terminal 6 6 C1P Charge-Pump Flying Capacitor Positive Terminal PGND Power Ground 7 7 CHOLD 8, 17, 20, 25, 26, 31, 32 Charge-Pump Hold Capacitor. Connect a 1F capacitor from CHOLD to VDD. 8 N.C. No Connection. Not internally connected. 6V Internal Regulator Output. Bypass with a 0.01F capacitor to AGND. 9 14 REG 10 13 AGND Analog Ground 11 -- IN- Negative Input 12 -- IN+ Positive Input 13 12 SS Soft-Start. Connect a 0.47F capacitor from SS to PGND to enable soft-start feature. 14 11 SHDN Active-Low Shutdown. Connect SHDN to PGND to disable the device. Connect to a logic-high for normal operation. 15 17 G1 Gain-Select Input 1 16 18 G2 Gain-Select Input 2 18 19 FS1 Frequency-Select Input 1 19 20 FS2 Frequency-Select Input 2 27, 28 -- OUT- Negative Audio Output 29, 30 -- OUT+ Positive Audio Output -- 9 INL- Left-Channel Negative Input -- 10 INL+ Left-Channel Positive Input -- 15 INR- Right-Channel Negative Input -- 16 INR+ Right-Channel Positive Input -- 25, 26 OUTR- Right-Channel Negative Audio Output -- 27, 28 OUTR+ Right-Channel Positive Audio Output -- 29, 30 OUTL- Left-Channel Negative Audio Output -- 31, 32 OUTL+ Left-Channel Positive Audio Output -- -- EP Exposed Paddle. Connect to PGND. www.maximintegrated.com Maxim Integrated 7 MAX9703/MAX9704 Detailed Description The MAX9703/MAX9704 filterless, Class D audio power amplifiers feature several improvements to switchmode amplifier technology. The MAX9703 is a mono amplifier, the MAX9704 is a stereo amplifier. These devices offer Class AB performance with Class D efficiency, while occupying minimal board space. A unique filterless modulation scheme and spread-spectrum switching mode create a compact, flexible, lownoise, efficient audio power amplifier. The differential input architecture reduces commonmode noise pickup, and can be used without input-coupling capacitors. The devices can also be configured as a single-ended input amplifier. Comparators monitor the device inputs and compare the complementary input voltages to the triangle waveform. The comparators trip when the input magnitude of the triangle exceeds their corresponding input voltage. Operating Modes Fixed-Frequency Modulation (FFM) Mode The MAX9703/MAX9704 feature three FFM modes with different switching frequencies (Table 1). In FFM mode, the frequency spectrum of the Class D output consists of the fundamental switching frequency and its associated harmonics (see the Wideband Output Spectrum (FFM Mode) graph in the Typical Operating Characteristics). The MAX9703/ MAX9704 allow the switching frequency to be changed by 35%, should the frequency of one or more of the harmonics fall in a sensitive band. This can be done at any time and does not affect audio reproduction. Spread-Spectrum Modulation (SSM) Mode The MAX9703/MAX9704 feature a unique spread-spectrum mode that flattens the wideband spectral components, improving EMI emissions that may be radiated by www.maximintegrated.com 10W Stereo/15W Mono, Filterless, Spread-Spectrum, Class D Amplifiers Table 1. Operating Modes FS1 FS2 SWITCHING MODE (kHz) L L 670 L H 940 H L 470 H H 670 7% the speaker and cables. This mode is enabled by setting FS1 = FS2 = H. In SSM mode, the switching frequency varies randomly by 7% around the center frequency (670kHz). 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 (see Figure 1). Efficiency Efficiency of a Class D amplifier is attributed to the region of 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 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 MAX9704 still exhibits >78% efficiency under the same conditions (Figure 2). Maxim Integrated 8 MAX9703/MAX9704 10W Stereo/15W Mono, Filterless, Spread-Spectrum, Class D Amplifiers VDD CIN L1* 1000pF CIN CIN L2* 1000pF MAX9704 L3* 1000pF CIN L4* 1000pF *L1-L4 = 0.05 DCR, 70 AT 100MHz, 3A FAIR RITE FERRITE BEAD (2512067007Y3). 40 AMPLITUDE (dBuV/m) 35 CE LIMIT 30 25 20 15 MAX9704 OUTPUT SPECTRUM 10 5 30 100 200 300 400 500 600 700 800 900 1000 FREQUENCY (MHz) Figure 1. MAX9704 EMI Spectrum, 9in PC Board trace, 3in Twisted-Pair Speaker Cable www.maximintegrated.com Maxim Integrated 9 MAX9703/MAX9704 EFFICIENCY vs. OUTPUT POWER 100 90 SS GPIO MUTE SIGNAL MAX9704 80 EFFICIENCY (%) 10W Stereo/15W Mono, Filterless, Spread-Spectrum, Class D Amplifiers 0.18F MAX9703/ MAX9704 70 60 50 Figure 3. MAX9703/MAX9704 Mute Circuit CLASS AB 40 30 20 VDD = 15V f = 1kHz RL = 8 10 0 0 2 4 6 8 10 12 14 16 18 20 OUTPUT POWER (W) Figure 2. MAX9704 Efficiency vs. Class AB Efficiency Shutdown The MAX9703/MAX9704 have a shutdown mode that reduces power consumption and extends battery life. Driving SHDN low places the device in low-power (0.2A) shutdown mode. Connect SHDN to a logic high for normal operation. Click-and-Pop Suppression The MAX9703/MAX9704 feature comprehensive clickand-pop suppression that eliminates audible transients on startup and shutdown. While in shutdown, the Hbridge is pulled to PGND through 330k. During startup, or powerup, the input amplifiers are muted and an internal loop sets the modulator bias voltages to the correct levels, preventing clicks and pops when the Hbridge is subsequently enabled. Following startup, a soft-start function gradually unmutes the input amplifiers. The value of the soft-start capacitor has an impact on the click/pop levels. For optimum performance, CSS should be at least 0.18F with a voltage rating of at least 7V. Mute Function The MAX9703/MA9704 features a clickless/popless mute mode. When the device is muted, the outputs stop switching, muting the speaker. Mute only affects the output stage and does not shut down the device. To mute the MAX9703/MAX9704, drive SS to PGND by using a MOSFET pulldown (Figure 3). Driving SS to PGND during the power-up/down or shutdown/turn-on cycle optimizes click-and-pop suppression. www.maximintegrated.com Applications Information Filterless 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 VDD peak-to-peak) and causes large ripple currents. Any parasitic resistance in the filter components results in a loss of power, lowering the efficiency. The MAX9703/MAX9704 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 MAX9703/MAX9704 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 > 30H. Typical 8 speakers exhibit series inductances in the range of 30H to 100H. Optimum efficiency is achieved with speaker inductances > 60H. Internal Regulator Output (VREG) The MAX9703/MAX9704 feature an internal, 6V regulator output (VREG). The MAX9703/MAX9704 REG output pin simplifies system design and reduces system cost by providing a logic voltage high for the MAX9703/ MAX9704 logic pins (G_, FS_). VREG is not available as a logic voltage high in shutdown mode. Do not apply VREG as a 6V potential to surrounding system components. Bypass REG with a 6.3V, 0.01F capacitor to AGND. Maxim Integrated 10 MAX9703/MAX9704 10W Stereo/15W Mono, Filterless, Spread-Spectrum, Class D Amplifiers Gain Selection The MAX9703/MAX9704 feature an internally set, logicselectable gain. The G1 and G2 logic inputs set the gain of the MAX9703/MAX9704 speaker amplifier (Table 2). SINGLE-ENDED AUDIO INPUT Table 2. Gain Selection IN+ MAX9703/ MAX9704 IN- G1 G2 GAIN (dB) 0 0 29.6 0 1 19.1 1 0 13 1 1 16 0.47F Figure 4. Single-Ended Input the signal to an optimum DC level. Assuming zero-source impedance, the -3dB point of the highpass filter is given by: Output Offset Unlike a Class AB amplifier, the output offset voltage of Class D amplifiers does not noticeably increase quiescent current draw when a load is applied. This is due to the power conversion of the Class D amplifier. For example, an 8mV DC offset across an 8 load results in 1mA extra current consumption in a class AB device. In the Class D case, an 8mV offset into 8 equates to an additional power drain of 8W. Due to the high efficiency of the Class D amplifier, this represents an additional quiescent current draw of: 8W/(VDD/100 x ), which is in the order of a few microamps. Input Amplifier Differential Input The MAX9703/MAX9704 feature a differential input structure, making them compatible with many CODECs, and offering improved noise immunity over a single-ended input amplifier. In devices such as PCs, noisy digital signals can be picked up by the amplifier's input traces. The signals appear at the amplifiers' inputs as commonmode noise. A differential input amplifier amplifies the difference of the two inputs, any signal common to both inputs is canceled. Single-Ended Input The MAX9703/MAX9704 can be configured as singleended input amplifiers by capacitively coupling either input to AGND and driving the other input (Figure 4). Component Selection Input Filter An input capacitor, CIN, in conjunction with the input impedance of the MAX9703/MAX9704, forms a highpass filter that removes the DC bias from an incoming signal. The AC-coupling capacitor allows the amplifier to bias www.maximintegrated.com 0.47F f -3dB = 1 2R INC IN Choose CIN so f-3dB is well below the lowest frequency of interest. Setting f-3dB too high affects the low-frequency response of the amplifier. Use capacitors with dielectrics that have low-voltage coefficients, such as tantalum or aluminum electrolytic. Capacitors with highvoltage coefficients, such as ceramics, may result in increased distortion at low frequencies. Charge-Pump Capacitor Selection Use capacitors with an ESR less than 100m for optimum performance. Low-ESR ceramic capacitors minimize the output resistance of the charge pump. For best performance over the extended temperature range, select capacitors with an X7R dielectric. Flying Capacitor (C1) The value of the flying capacitor (C1) affects the load regulation and output resistance of the charge pump. A C1 value that is too small degrades the device's ability to provide sufficient current drive. Increasing the value of C1 improves load regulation and reduces the chargepump output resistance to an extent. Above 1F, the onresistance of the switches and the ESR of C1 and C2 dominate. Hold Capacitor (C2) The output capacitor value and ESR directly affect the ripple at CHOLD. Increasing 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. Output Filter The MAX9703/MAX9704 do not require an output filter and can pass FCC emissions standards with unshielded speaker cables. However, output filtering can be used if a Maxim Integrated 11 MAX9703/MAX9704 design is failing radiated emissions due to board layout or cable length, or the circuit is near EMIsensitive devices. Use a ferrite bead filter when radiated frequencies above 10MHz are of concern. Use an LC filter when radiated frequencies below 10MHz are of concern, or when long leads connect the amplifier to the speaker. Refer to the MAX9704 Evaluation Kit schematic for details of this filter. Sharing Input Sources In certain systems, a single audio source can be shared by multiple devices (speaker and headphone amplifiers). When sharing inputs, it is common to mute the unused device, rather than completely shutting it down, preventing the unused device inputs from distorting the input signal. Mute the MAX9703/MAX9704 by driving SS low through an open-drain output or MOSFET (see the System Diagram). Driving SS low turns off the Class D output stage, but does not affect the input bias levels of the MAX9703/MAX9704. Be aware that during normal operation, the voltage at SS can be up to 7V, depending on the MAX9703/MAX9704 supply. Supply Bypassing/Layout Proper power-supply bypassing ensures low distortion operation. For optimum performance, bypass VDD to PGND with a 0.1F capacitor as close to each VDD pin as possible. A low-impedance, high-current power-supply connection to VDD is assumed. Additional bulk capacitance should be added as required depending on the application and power-supply characteristics. AGND and PGND should be star connected to system ground. Refer to the MAX9704 Evaluation Kit for layout guidance. Class D Amplifier Thermal Considerations 10W Stereo/15W Mono, Filterless, Spread-Spectrum, Class D Amplifiers Audio content, both music and voice, has a much lower RMS value relative to its peak output power. Figure 5 shows a sine wave and an audio signal in the time domain. Both are measured for RMS value by the oscilloscope. Although the audio signal has a slightly higher peak value than the sine wave, its RMS value is almost half that of the sine wave. Therefore, while an audio signal may reach similar peaks as a continuous sine wave, the actual thermal impact on the Class D amplifier is highly reduced. If the thermal performance of a system is being evaluated, it is important to use actual audio signals instead of sine waves for testing. If sine waves must be used, the thermal performance will be less than the system's actual capability. PC Board Thermal Considerations The exposed pad is the primary route of keeping heat away from the IC. With a bottom-side exposed pad, the PC board and its copper becomes the primary heatsink for the Class D amplifier. Solder the exposed pad to a large copper polygon. Add as much copper as possible from this polygon to any adjacent pin on the Class D amplifier as well as to any adjacent components, provided these connections are at the same potential. These copper paths must be as wide as possible. Each of these paths contributes to the overall thermal capabilities of the system. The copper polygon to which the exposed pad is attached should have multiple vias to the opposite side of the PC board, where they connect to another copper polygon. Make this polygon as large as possible within the system's constraints for signal routing. Class D amplifiers provide much better efficiency and thermal performance than a comparable Class AB amplifier. However, the system's thermal performance must be considered with realistic expectations and include consideration of many parameters. This section examines Class D amplifiers using general examples to illustrate good design practices. Continuous Sine Wave vs. Music When a Class D amplifier is evaluated in the lab, often a continuous sine wave is used as the signal source. While this is convenient for measurement purposes, it represents a worst-case scenario for thermal loading on the amplifier. It is not uncommon for a Class D amplifier to enter thermal shutdown if driven near maximum output power with a continuous sine wave. www.maximintegrated.com 20ms/div Figure 5. RMS Comparison of Sine Wave vs. Audio Signal Maxim Integrated 12 MAX9703/MAX9704 Additional improvements are possible if all the traces from the device are made as wide as possible. Although the IC pins are not the primary thermal path of the package, they do provide a small amount. The total improvement would not exceed about 10%, but it could make the difference between acceptable performance and thermal problems. Auxiliary Heatsinking 10W Stereo/15W Mono, Filterless, Spread-Spectrum, Class D Amplifiers Decreasing the ambient temperature or reducing JA will improve the die temperature of the MAX9704. JA can be reduced by increasing the copper size/weight of the ground plane connected to the exposed paddle of the MAX9704 TQFN package. Additionally, JA can be reduced by attaching a heatsink, adding a fan, or mounting a vertical PC board. If operating in higher ambient temperatures, it is possible to improve the thermal performance of a PC board with the addition of an external heatsink. The thermal resistance to this heatsink must be kept as low as possible to maximize its performance. With a bottom-side exposed pad, the lowest resistance thermal path is on the bottom of the PC board. The topside of the IC is not a significant thermal path for the device, and therefore is not a costeffective location for a heatsink. Load Impedance Thermal Calculations Although most loudspeakers are either 4 or 8, there are other impedances available which can provide a more thermally efficient solution. The die temperature of a Class D amplifier can be estimated with some basic calculations. For example, the die temperature is calculated for the below conditions: TA = +40C POUT = 2x8W = 16W RL = 16 Efficiency () = 87% JA = 27C/W First, the Class D amplifier's power dissipation must be calculated. PDISS = POUT 16W - POUT = - 16W = 2.4W 0.87 Then the power dissipation is used to calculate the die temperature, TC, as follows: TC = TA + PDISS x JA = 40C + 2.4W x 27C/W = 104.8C www.maximintegrated.com The on-resistance of the MOSFET output stage in Class D amplifiers affects both the efficiency and the peakcurrent capability. Reducing the peak current into the load reduces the I2R losses in the MOSFETs, thereby increasing efficiency. To keep the peak currents lower, choose the highest impedance speaker which can still deliver the desired output power within the voltage swing limits of the Class D amplifier and its supply voltage. Another consideration is the load impedance across the audio frequency band. A loudspeaker is a complex electromechanical system with a variety of resonances. In other words, an 8 speaker is usually only 8 impedance within a very narrow range, and often extends well below 8, reducing the thermal efficiency below what is expected. This lower-than-expected impedance can be further reduced when a crossover network is used in a multi-driver audio system. Optimize MAX9703/MAX9704 Efficiency with Load Impedance and Supply Voltage To optimize the efficiency of the MAX9703/MAX9704, load the output stage with 12 to 16 speakers. The MAX9703/MAX9704 exhibits highest efficiency performance when driving higher load impedance (see the Typical Operating Characteristics). If a 12 to 16 load is not available, select a lower supply voltage when driving 6 to 10 loads. Maxim Integrated 13 MAX9703/MAX9704 10W Stereo/15W Mono, Filterless, Spread-Spectrum, Class D Amplifiers Functional Diagrams 10V TO 25V 100F* 25V 0.1F 25V 1 2 PGND 0.47F 0.47F 0.18F 10V 11 IN18 FS1 19 FS2 VREG 14 SHDN 15 G1 VREG 0.01F 10V 3 4 VDD 21 22 23 24 VDD PGND 12 IN+ VREG VREG VREG 0.1F 25V 16 G2 13 SS 9 REG OUT+ 30 MODULATOR OUT- 27 OSCILLATOR MAX9703 GAIN CONTROL SHUTDOWN CONTROL C1P 6 CHARGE PUMP 5 C1N 10 AGND LOGIC INPUTS SHOWN FOR AV = 16dB (SSM). VIN = LOGIC HIGH > 2.5V. CHOOSE CAPACITOR VOLTAGE RATING V . DD *SYSTEM-LEVEL REQUIREMENT. C1 0.1F 25V CHOLD 7 www.maximintegrated.com OUT+ 29 OUT- 28 H-BRIDGE VDD C2 1F 25V Maxim Integrated 14 MAX9703/MAX9704 10W Stereo/15W Mono, Filterless, Spread-Spectrum, Class D Amplifiers Functional Diagrams (continued) 10V TO 25V 100F* 25V 0.1F 25V 1 2 PGND 0.47F 0.47F VREG VREG 0.47F 0.47F VREG VREG 0.18F 10V VREG 0.01F 10V 0.1F 25V 3 4 VDD 21 22 23 24 VDD PGND 10 INL+ 9 INL- 19 FS1 20 FS2 OUTL+ 32 MODULATOR OUTL+ 31 OUTL- 30 H-BRIDGE OUTL- 29 OSCILLATOR 16 INR+ 15 INR- 11 SHDN 17 G1 18 G2 12 SS 14 REG OUTR+ 28 MODULATOR OUTR+ 27 OUTR- 26 H-BRIDGE OUTR- 25 GAIN CONTROL SHUTDOWN CONTROL MAX9704 C1P 6 CHARGE PUMP 5 C1N 13 AGND C1 0.1F 25V CHOLD 7 VDD C2 1F 25V LOGIC INPUTS SHOWN FOR AV = 16dB (SSM). VIN = LOGIC HIGH > 2.5V. CHOOSE CAPACITOR VOLTAGE RATING V . DD *SYSTEM-LEVEL REQUIREMENT. www.maximintegrated.com Maxim Integrated 15 MAX9703/MAX9704 10W Stereo/15W Mono, Filterless, Spread-Spectrum, Class D Amplifiers System Diagram VDD 100F* 1F 0.47F OUTL- VDD SHDN INL- OUTL- INL+ OUTL+ 0.47F OUTL+ CODEC MAX9704 0.47F OUTR+ INR+ OUTR+ INR- OUTR- 0.47F OUTR- 5V SS 100k 0.18F SHDN 1F VDD INL1F 15k 1F 15k MAX9722B INL+ OUTL INR+ OUTR INR- PVSS SVSS 1F 30k 30k C1P CIN 1F 1F LOGIC INPUTS SHOWN FOR AV = 16dB (SSM). *BULK CAPACITANCE, IF NEEDED. www.maximintegrated.com Maxim Integrated 16 MAX9703/MAX9704 10W Stereo/15W Mono, Filterless, Spread-Spectrum, Class D Amplifiers Pin Configurations PGND VDD VDD N.C. FS2 FS1 N.C. PGND PGND VDD VDD FS2 FS1 G2 24 23 22 21 20 19 18 17 24 23 22 21 20 19 18 17 N.C. 25 16 G2 G1 PGND TOP VIEW OUTR- 25 16 INR+ N.C. 26 15 G1 OUTR- 26 15 INR- OUT- 27 14 SHDN OUTR+ 27 14 REG. 13 AGND OUT- 28 13 SS OUTR+ 28 OUT+ 29 12 IN+ OUTL- 29 12 SS OUT+ 30 11 IN- OUTL- 30 11 SHDN N.C. 31 10 AGND OUTL+ 31 10 INL+ N.C. 32 9 OUTL+ 32 9 TQFN (5mm x 5mm) 4 5 6 7 INL- 8 N.C. 3 C1P 2 CHOLD 1 VDD VDD C1N 8 C1N VDD 7 VDD PGND 6 PGND 5 PGND 4 N.C. 3 C1P 2 REG. MAX9704 CHOLD 1 PGND MAX9703 TQFN (7mm x 7mm) Chip Information MAX9703 TRANSISTOR COUNT: 3093 MAX9704 TRANSISTOR COUNT: 4630 PROCESS: BiCMOS www.maximintegrated.com Maxim Integrated 17 MAX9703/MAX9704 10W Stereo/15W Mono, Filterless, Spread-Spectrum, Class D Amplifiers Package Information For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a "+", "#", or "-" in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. PACKAGE TYPE PACKAGE CODE OUTLINE NO. LAND PATTERN NO. 32 TQFN-EP (Mono) T3255-4 21-0144 90-0012 32 TQFN-EP (Stereo) T3277-2 21-0140 90-0125 www.maximintegrated.com Maxim Integrated 18 MAX9703/MAX9704 10W Stereo/15W Mono, Filterless, Spread-Spectrum, Class D Amplifiers Package Information (continued) For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a "+", "#", or "-" in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. www.maximintegrated.com Maxim Integrated 19 MAX9703/MAX9704 10W Stereo/15W Mono, Filterless, Spread-Spectrum, Class D Amplifiers Package Information (continued) For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a "+", "#", or "-" in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. www.maximintegrated.com Maxim Integrated 20 MAX9703/MAX9704 10W Stereo/15W Mono, Filterless, Spread-Spectrum, Class D Amplifiers Package Information (continued) For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a "+", "#", or "-" in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. www.maximintegrated.com Maxim Integrated 21 MAX9703/MAX9704 10W Stereo/15W Mono, Filterless, Spread-Spectrum, Class D Amplifiers Package Information (continued) For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a "+", "#", or "-" in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. www.maximintegrated.com Maxim Integrated 22 MAX9703/MAX9704 10W Stereo/15W Mono, Filterless, Spread-Spectrum, Class D Amplifiers Package Information (continued) For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a "+", "#", or "-" in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. www.maximintegrated.com Maxim Integrated 23 MAX9703/MAX9704 10W Stereo/15W Mono, Filterless, Spread-Spectrum, Class D Amplifiers Revision History REVISION NUMBER REVISION DATE 8 5/14 PAGES CHANGED DESCRIPTION Removed automotive reference in Applications section and corrected package code 1 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated's website at www.maximintegrated.com. Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance. Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc. (c) 2014 Maxim Integrated Products, Inc. 24 Mouser Electronics Authorized Distributor Click to View Pricing, Inventory, Delivery & Lifecycle Information: Maxim Integrated: MAX9703ETJ+ MAX9704ETJ+ MAX9703ETJ+T MAX9704ETJ+T MAX1782ETM+C8C MAX9703DEVBRD