19-3030; Rev 2; 10/08 1.2W, Low-EMI, Filterless, Class D Audio Amplifier The MAX9700 mono class D audio power amplifier provides class AB amplifier performance with class D efficiency, conserving board space and extending battery life. Using a class D architecture, the MAX9700 delivers 1.2W into an 8Ω load while offering efficiencies above 90%. A patented, low-EMI modulation scheme renders the traditional class D output filter unnecessary. The MAX9700 offers two modulation schemes: a fixedfrequency (FFM) mode, and a spread-spectrum (SSM) mode that reduces EMI-radiated emissions due to the modulation frequency. Furthermore, the MAX9700 oscillator can be synchronized to an external clock through the SYNC input, allowing the switching frequency to be user defined. The SYNC input also allows multiple MAX9700s to be cascaded and frequency locked, minimizing interference due to clock intermodulation. The device utilizes a fully differential architecture, a fullbridged output, and comprehensive click-and-pop suppression. The gain of the MAX9700 is set internally (MAX9700A: 6dB, MAX9700B: 12dB, MAX9700C: 15.6dB, MAX9700D: 20dB), further reducing external component count. The MAX9700 features high 72dB PSRR, a low 0.01% THD+N, and SNR in excess of 90dB. Short-circuit and thermal-overload protection prevent the device from damage during a fault condition. The MAX9700 is available in 10-pin TDFN (3mm ✕ 3mm ✕ 0.8mm), 10-pin µMAX®, and 12-bump UCSP™ (1.5mm ✕ 2mm ✕ 0.6mm) packages. The MAX9700 is specified over the extended -40°C to +85°C temperature range. Applications Cellular Phones MP3 Players PDAs Portable Audio Block Diagram Features ♦ Filterless Amplifier Passes FCC Radiated Emissions Standards with 100mm of Cable ♦ Unique Spread-Spectrum Mode Offers 5dB Emissions Improvement Over Conventional Methods ♦ Optional External SYNC Input ♦ Simple Master-Slave Setup for Stereo Operation ♦ 94% Efficiency ♦ 1.2W into 8Ω ♦ Low 0.01% THD+N ♦ High PSRR (72dB at 217Hz) ♦ Integrated Click-and-Pop Suppression ♦ Low Quiescent Current (4mA) ♦ Low-Power Shutdown Mode (0.1µA) ♦ Short-Circuit and Thermal-Overload Protection ♦ Available in Thermally Efficient, Space-Saving Packages 10-Pin TDFN (3mm x 3mm x 0.8mm) 10-Pin µMAX 12-Bump UCSP (1.5mm x 2mm x 0.6mm) Ordering Information TEMP RANGE PINPACKAGE MAX9700AETB -40oC to +85oC 10 TDFN-EP* MAX9700AEUB -40oC to +85oC 10 µMAX PART o o TOP MARK ACM — MAX9700AEBC-T -40 C to +85 C 12 UCSP MAX9700BETB -40oC to +85oC 10 TDFN-EP* MAX9700BEUB -40oC to +85oC 10 µMAX — 12 UCSP — o MAX9700BEBC-T o -40 C to +85 C — ACI *EP = Exposed pad. Ordering Information continued and Selector Guide appears at end of data sheet. VDD Pin Configurations DIFFERENTIAL AUDIO INPUT SYNC INPUT MODULATOR AND H-BRIDGE OSCILLATOR MAX9700 TOP VIEW VDD 1 IN+ 2 IN- 3 GND SHDN 10 PVDD 9 OUT- 8 OUT+ 4 7 PGND 5 6 SYNC MAX9700 TDFN/μMAX UCSP is a trademark of Maxim Integrated Products, Inc. µMAX is a registered trademark of Maxim Integrated Products, Inc. Pin Configurations continued at end of data sheet. ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 1 MAX9700 General Description MAX9700 1.2W, Low-EMI, Filterless, Class D Audio Amplifier ABSOLUTE MAXIMUM RATINGS VDD to GND..............................................................................6V PVDD to PGND .........................................................................6V GND to PGND .......................................................-0.3V to +0.3V All Other Pins to GND.................................-0.3V to (VDD + 0.3V) Continuous Current Into/Out of PVDD/PGND/OUT_........±600mA Continuous Input Current (all other pins) .........................±20mA Duration of OUT_ Short Circuit to GND or PVDD ........Continuous Duration of Short Circuit Between OUT+ and OUT- ..Continuous Continuous Power Dissipation (TA = +70°C) 10-Pin TDFN (derate 24.4mW/°C above +70°C) .....1951.2mW 10-Pin µMAX (derate 5.6mW/oC above +70°C) .........444.4mW 12-Bump UCSP (derate 6.1mW/°C above +70°C)........484mW 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 Bump Temperature (soldering) Reflow ..........................................................................+235°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 = V SHDN = 3.3V, VGND = VPGND = 0V, SYNC = GND (FFM), RL = 8Ω, RL connected between OUT+ and OUT-, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Notes 1, 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS GENERAL Supply Voltage Range VDD 5.5 V Quiescent Current IDD Inferred from PSRR test 2.5 4 5.2 mA Shutdown Current ISHDN 0.1 10 µA Turn-On Time tON Input Resistance RIN TA = +25°C 12 20 VBIAS Either input 0.73 0.83 Input Bias Voltage Voltage Gain Output Offset Voltage Common-Mode Rejection Ratio Power-Supply Rejection Ratio (Note 3) Output Power Total Harmonic Distortion Plus Noise 2 AV VOS CMRR 30 MAX9700A 6 MAX9700B 12 MAX9700C 15.6 MAX9700D 20 TA = +25°C ±11 TMIN ≤ TA ≤ TMAX fIN = 1kHz, input referred POUT THD+N 200mVP-P ripple THD+N = 1% fIN = 1kHz, either FFM or SSM kΩ 0.93 72 50 V dB ±80 ±120 VDD = 2.5V to 5.5V, TA = +25°C PSRR ms mV dB 70 fRIPPLE = 217Hz 72 fRIPPLE = 20kHz 55 RL = 8Ω 450 RL = 6Ω 800 RL = 8Ω, POUT = 125mW 0.01 RL = 6Ω, POUT = 125mW 0.01 dB mW % _______________________________________________________________________________________ 1.2W, Low-EMI, Filterless, Class D Audio Amplifier (VDD = PVDD = V SHDN = 3.3V, VGND = VPGND = 0V, SYNC = GND (FFM), RL = 8Ω, RL connected between OUT+ and OUT-, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Notes 1, 2) PARAMETER SYMBOL CONDITIONS MIN BW = 22Hz to 22kHz Signal-to-Noise Ratio SNR VOUT = 2VRMS A-weighted Oscillator Frequency fOSC FFM 89 SSM 87 FFM 92 SSM UNITS dB 90 980 1100 1220 SYNC = unconnected 1280 1450 1620 kHz 1220 ±120 SYNC Frequency Lock Range 800 η MAX SYNC = GND SYNC = VDD (SSM mode) Efficiency TYP POUT = 500mW, fIN = 1kHz 2000 94 kHz % DIGITAL INPUTS (SHDN, SYNC) VIH Input Thresholds 2 0.8 VIL V SHDN Input Leakage Current ±1 µA SYNC Input Current ±5 µA ELECTRICAL CHARACTERISTICS (VDD = PVDD = V SHDN = 5V, VGND = VPGND = 0V, SYNC = GND (FFM), RL = 8Ω, RL connected between OUT+ and OUT-, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Notes 1, 2) PARAMETER Quiescent Current SYMBOL CONDITIONS MIN IDD 5.2 Shutdown Current ISHDN Common-Mode Rejection Ratio CMRR f = 1kHz, input referred Power-Supply Rejection Ratio PSRR 200mVP-P ripple Output Power POUT Total Harmonic Distortion Plus Noise Signal-to-Noise Ratio THD+N SNR TYP THD+N = 1% f = 1kHz, either FFM or SSM VOUT = 3VRMS mA µA 72 dB 72 f = 20kHz 55 RL = 16Ω 700 RL = 8Ω 1200 RL = 6Ω 1600 RL = 8Ω, POUT = 125mW 0.015 RL = 4Ω, POUT = 125mW 0.02 A-weighted UNITS 0.1 f = 217Hz BW = 22Hz to 22kHz MAX FFM 92.5 SSM 90.5 FFM 95.5 SSM 93.5 dB mW % dB 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 = 4Ω, L = 33µH. For RL = 8Ω, L = 68µH. For RL = 16Ω, L = 136µH. Note 3: PSRR is specified with the amplifier inputs connected to GND through CIN. _______________________________________________________________________________________ 3 MAX9700 ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (VDD = 3.3V, SYNC = GND (SSM), TA = +25°C, unless otherwise noted.) 1 1 1 VDD = +3.3V RL = 8Ω 0.1 POUT = 300mW POUT = 125mW 0.001 FFM MODE 0.001 0.001 10 100 SSM MODE 0.01 0.01 POUT = 125mW 1k 10k 100k 10 100 1k 10k 10 100k 100 1k 10k 100k FREQUENCY (Hz) FREQUENCY (Hz) FREQUENCY (Hz) TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT VOLTAGE f = 1kHz f = 100Hz 0.1 0.01 1 f = 10kHz 0.1 VDD = 5V RL = 4Ω 10 0.5 1.0 1.5 2.0 f = 10kHz f = 1kHz 0.001 0.001 0 f = 100Hz 0.1 f = 100Hz f = 1kHz 0.001 1 0.01 0.01 f = 10kHz MAX9700 toc06 100 MAX9700 toc05 10 THD+N (%) 1 VDD = 5V RL = 16Ω THD+N (%) VDD = 5V RL = 8Ω 10 100 MAX9700 toc04 100 0 0.2 0.4 0.6 0.8 0 1.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 OUTPUT POWER (W) OUTPUT POWER (W) OUTPUT POWER (W) TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER 1 DIFFERENTIAL INPUT 0.1 0.01 FFM (SYNC = GND) 1 SSM 0.1 0.2 0.3 OUTPUT POWER (W) 0.4 0.5 MAX9700 toc09 1 fSYNC = 800kHz 0.1 0.01 fSYNC = 2MHz 0.001 0.1 10 FFM (SYNC UNCONNECTED) 0.001 0 VDD = 5V f = 1kHz RL = 8Ω fSYNC = 1.4MHz 0.01 SINGLE ENDED 100 MAX9700 toc08 VDD = 5V f = 1kHz RL = 8Ω 10 THD+N (%) VDD = 2.5V RL = 8Ω VCM = 1.25V NO INPUT CAPACITORS 10 100 MAX9700 toc07 100 THD+N (%) THD+N (%) THD+N (%) THD+N (%) POUT = 300mW 0.01 4 VDD = +3.3V RL = 8Ω POUT = 125mW 0.1 THD+N (%) 0.1 MAX9700 toc03 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY MAX9700 toc02 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY MAX9700 toc01 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY VDD = +5V RL = 8Ω THD+N (%) MAX9700 1.2W, Low-EMI, Filterless, Class D Audio Amplifier 0.001 0 0.5 1.0 OUTPUT POWER (W) 1.5 2.0 0 0.5 1.0 OUTPUT POWER (W) _______________________________________________________________________________________ 1.5 2.0 1.2W, Low-EMI, Filterless, Class D Audio Amplifier TOTAL HARMONIC DISTORTION PLUS NOISE vs. COMMON-MODE VOLTAGE 80 RL = 8Ω RL = 4Ω 90 80 60 50 40 VDD = 3.3V f = 1kHz 10 1.5 2.0 2.5 3.0 0.3 0.6 COMMON-MODE VOLTAGE (V) EFFICIENCY vs. SUPPLY VOLTAGE EFFICIENCY (%) RL = 4Ω 60 50 40 40 20 f = 1kHz POUT = MAX (THD+N = 1%) 10 0 2.5 3.0 3.5 4.0 4.5 5.0 VDD = 3.3V f = 1kHz POUT = 300mW RL = 8Ω 10 0 5.5 800 1000 1200 1400 1600 1800 f = 1kHz RL = 4Ω THD+N = 10% 3.0 RL = 4Ω THD+N = 1% 2.5 RL = 8Ω THD+N = 10% 2.0 1.5 1.0 0.5 RL = 8Ω THD+N = 1% 0 2.5 2000 3.0 3.5 4.0 4.5 5.0 SUPPLY VOLTAGE (V) SYNC FREQUENCY (kHz) SUPPLY VOLTAGE (V) OUTPUT POWER vs. LOAD RESISTANCE COMMON-MODE REJECTION RATIO vs. FREQUENCY POWER-SUPPLY REJECTION RATIO vs. FREQUENCY -20 VDD = 5V CMRR (dB) 1200 800 VDD = 3.3V INPUT REFERRED VIN = 200mVP-P 0 -20 -30 -40 -40 -60 -50 -60 -70 -70 400 -80 -80 -90 -90 0 -100 -100 0 10 20 30 40 50 60 70 80 90 100 LOAD RESISTANCE (Ω) 10 100 1k FREQUENCY (Hz) 10k 100k OUTPUT REFERRED INPUTS AC GROUNDED VDD = 3.3V -10 -30 -50 5.5 MAX9700TOC18 1600 0 -10 PSRR (dB) f = 1kHz THD+N = 1% MAX9700TOC17 2000 OUTPUT POWER (mW) 50 30 3.5 3.0 2.5 OUTPUT POWER vs. SUPPLY VOLTAGE 60 20 2.0 EFFICIENCY vs. SYNC INPUT FREQUENCY 70 30 1.5 OUTPUT POWER (W) 80 RL = 8Ω 70 1.0 0.5 OUTPUT POWER (W) 90 MAX9700toc16 EFFICIENCY (%) 80 VDD = 5V f = 1kHz 0 1.5 1.2 MAx9700 toc14 90 0.9 100 MAX9700 toc13 100 40 0 0 OUTPUT POWER (W) 1.0 50 10 0 0.5 60 20 20 0 RL = 4Ω 30 30 0.01 RL = 8Ω 70 MAX9700toc15 0.1 70 MAX9700toc12 90 EFFICIENCY (%) 1 100 MAX9700toc11 MAX9700 toc10 VDD = 3.3V RL = 8Ω f = 1kHz POUT = 300mW DIFFERENTIAL INPUT EFFICIENCY vs. OUTPUT POWER EFFICIENCY vs. OUTPUT POWER 100 EFFICIENCY (%) THD+N (%) 10 10 100 1k 10k 100k FREQUENCY (Hz) _______________________________________________________________________________________ 5 MAX9700 Typical Operating Characteristics (continued) (VDD = 3.3V, SYNC = GND (SSM), TA = +25°C, unless otherwise noted.) Typical Operating Characteristics (continued) (VDD = 3.3V, SYNC = GND (SSM), TA = +25°C, unless otherwise noted.) OUTPUT FREQUENCY SPECTRUM GSM POWER-SUPPLY REJECTION MAX9700 toc19 MAX9700 OUTPUT OUTPUT MAGNITUDE (dBV) 500mV/div VDD 100μV/div MAX9700 toc20 0 FFM MODE VOUT = -60dBV f = 1kHz RL = 8Ω UNWEIGHTED -20 -40 -60 -80 -100 -120 -140 0 -40 SSM MODE VOUT = -60dBV f = 1kHz RL = 8Ω A-WEIGHTED -20 OUTPUT MAGNITUDE (dBV) -20 0 MAX9700 toc21 SSM MODE VOUT = -60dBV f = 1kHz RL = 8Ω UNWEIGHTED 10k 15k FREQUENCY (Hz) -60 -80 -100 -40 -60 -80 -100 0 RBW = 10kHz -10 -20 -30 -40 -50 -60 -70 -80 -120 -140 -140 5k 10k 15k FREQUENCY (Hz) -90 -100 0 20k 5k 10k 15k FREQUENCY (Hz) WIDEBAND OUTPUT SPECTRUM (SSM MODE) MAX9700 toc24 RBW = 10kHz -20 OUTPUT AMPLITUDE (dB) 1M 10M 100M FREQUENCY (Hz) TURN-ON/TURN-OFF RESPONSE 0 -10 20k MAX9700 toc25 -120 0 SHDN 3V -30 -40 -50 0V -60 -70 MAX9700 OUTPUT -80 250mV/div -90 -100 1M 10M 100M FREQUENCY (Hz) 6 20k WIDEBAND OUTPUT SPECTRUM (FFM MODE) OUTPUT FREQUENCY SPECTRUM OUTPUT FREQUENCY SPECTRUM 0 5k MAX9700 toc23 DUTY CYCLE = 88% RL = 8Ω OUTPUT AMPLITUDE (dB) 2ms/div MAX9700 toc22 f = 217Hz INPUT LOW = 3V INPUT HIGH = 3.5V OUTPUT MAGNITUDE (dBV) MAX9700 1.2W, Low-EMI, Filterless, Class D Audio Amplifier 1G f = 1kHz RL = 8Ω 10ms/div _______________________________________________________________________________________ 1G 1.2W, Low-EMI, Filterless, Class D Audio Amplifier TA = +85°C 5.0 TA = +25°C 4.5 TA = -40°C 4.0 TA = +85°C 0.14 SUPPLY CURRENT (μA) SUPPLY CURRENT (mA) 5.5 0.16 MAX9700 toc26 6.0 MAX9700 toc27 SHUTDOWN SUPPLY CURRENT vs. SUPPLY VOLTAGE SUPPLY CURRENT vs. SUPPLY VOLTAGE 0.12 0.10 TA = +25°C 0.08 0.06 0.04 3.5 TA = -40°C 0.02 0 3.0 2.5 3.0 3.5 4.0 4.5 SUPPLY VOLTAGE (V) 5.0 2.5 5.5 3.0 3.5 4.0 4.5 5.0 5.5 SUPPLY VOLTAGE (V) Functional Diagram VDD 1μF 5 (B2) SHDN 1 (A1) 10 (B4) 6 (A3) VDD PVDD SYNC UVLO/POWER MANAGEMENT CLICK-AND-POP SUPPRESSION OSCILLATOR PVDD 1μF 2 (B1) IN+ 1μF 3 (C1) IN- CLASS D MODULATOR 8 OUT+ (A4) PGND PVDD OUT- 9 (C4) MAX9700 PGND PGND 7 (B3) GND 4 (C2) ( ) UCSP BUMP. _______________________________________________________________________________________ 7 MAX9700 Typical Operating Characteristics (continued) (VDD = 3.3V, SYNC = GND (SSM), TA = +25°C, unless otherwise noted.) 1.2W, Low-EMI, Filterless, Class D Audio Amplifier MAX9700 Pin Description PIN BUMP TDFN/µMAX UCSP 1 2 NAME FUNCTION A1 VDD Analog Power Supply. Connect to an external power supply. Bypass to GND with a 1µF capacitor. B1 IN+ Noninverting Audio Input Inverting Audio Input 3 C1 IN- 4 C2 GND 5 B2 SHDN Active-Low Shutdown Input. Connect to VDD for normal operation. Analog Ground 6 A3 SYNC Frequency Select and External Clock Input. SYNC = GND: Fixed-frequency mode with fS = 1100kHz. SYNC = Unconnected: Fixed-frequency mode with fS = 1450kHz. SYNC = VDD: Spread-spectrum mode with fS = 1220kHz ±120kHz. SYNC = Clocked: Fixed-frequency mode with fS = external clock frequency. 7 B3 PGND Power Ground 8 A4 OUT+ Amplifier-Output Positive Phase 9 C4 OUT- Amplifier-Output Negative Phase 10 B4 PVDD H-Bridge Power Supply. Connect to VDD. — — EP Exposed Pad. Internallly connected to GND. Connect to a large ground plane to maximize thermal performance. Not intended as an electrical connection point. (TDFN package only.) Detailed Description Operating Modes The MAX9700 filterless, class D audio power amplifier features several improvements to switch-mode amplifier technology. The MAX9700 offers class AB performance with class D efficiency, while occupying minimal board space. A unique filterless modulation scheme, synchronizable switching frequency, and SSM mode create a compact, flexible, low-noise, efficient audio power amplifier. The differential input architecture reduces common-mode noise pickup, and can be used without input-coupling capacitors. The device can also be configured as a single-ended input amplifier. Fixed-Frequency Modulation (FFM) Mode The MAX9700 features two FFM modes. The FFM modes are selected by setting SYNC = GND for a 1.1MHz switching frequency, and SYNC = UNCONNECTED for a 1.45MHz switching frequency. In FFM mode, the frequency spectrum of the class D output consists of the fundamental switching frequency and its associated harmonics (see the Wideband FFT graph in the Typical Operating Characteristics). The MAX9700 allows the switching frequency to be changed by +32%, 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. Comparators monitor the MAX9700 inputs and compare the complementary input voltages to the sawtooth waveform. The comparators trip when the input magnitude of the sawtooth exceeds their corresponding input voltage. Both comparators reset at a fixed time after the rising edge of the second comparator trip point, generating a minimum-width pulse tON(MIN) at the output of the second comparator (Figure 1). As the input voltage increases or decreases, the duration of the pulse at one output increases (the first comparator to trip) while the other output pulse duration remains at tON(MIN). This causes the net voltage across the speaker (VOUT+ VOUT-) to change. 8 Spread-Spectrum Modulation (SSM) Mode The MAX9700 features a unique, patented spread-spectrum mode that flattens the wideband spectral components, improving EMI emissions that may be radiated by the speaker and cables by 5dB. Proprietary techniques ensure that the cycle-to-cycle variation of the switching period does not degrade audio reproduction or efficiency (see the Typical Operating Characteristics). Select SSM mode by setting SYNC = VDD. In SSM mode, the switching frequency varies randomly by ±120kHz around the center frequency (1.22MHz). The modulation _______________________________________________________________________________________ 1.2W, Low-EMI, Filterless, Class D Audio Amplifier MAX9700 tSW VIN- VIN+ OUT- OUT+ tON(MIN) VOUT+ - VOUT- Figure 1. MAX9700 Outputs with an Input Signal Applied Table 1. Operating Modes SYNC INPUT MODE GND FFM with fS = 1100kHz UNCONNECTED FFM with fS = 1450kHz VDD Clocked SSM with fS = 1220kHz ±120kHz FFM with fS = external clock frequency scheme remains the same, but the period of the sawtooth waveform changes from cycle to cycle (Figure 2). Instead of a large amount of spectral energy present at multiples of the switching frequency, the energy is now spread over a bandwidth that increases with frequency. Above a few megahertz, the wideband spectrum looks like white noise for EMI purposes (Figure 3). External Clock Mode The SYNC input allows the MAX9700 to be synchronized to a system clock (allowing a fully synchronous system), or allocating the spectral components of the switching harmonics to insensitive frequency bands. Applying an external TTL clock of 800kHz to 2MHz to SYNC synchronizes the switching frequency of the MAX9700. The period of the SYNC clock can be randomized, enabling the MAX9700 to be synchronized to another MAX9700 operating in SSM mode. Filterless Modulation/Common-Mode Idle The MAX9700 uses Maxim’s unique, patented modulation scheme that eliminates the LC filter required by traditional class D amplifiers, improving efficiency, reducing component count, and conserving board space and system cost. Conventional class D amplifiers _______________________________________________________________________________________ 9 MAX9700 1.2W, Low-EMI, Filterless, Class D Audio Amplifier tSW tSW tSW tSW VIN- VIN+ OUT- OUT+ tON(MIN) VOUT+ - VOUT- Figure 2. MAX9700 Output with an Input Signal Applied (SSM Mode) output a 50% duty cycle square wave when no signal is present. With no filter, the square wave appears across the load as a DC voltage, resulting in finite load current, increasing power consumption. When no signal is present at the input of the MAX9700, the outputs switch as shown in Figure 4. Because the MAX9700 drives the speaker differentially, the two outputs cancel each other, resulting in no net Idle Mode™ voltage across the speaker, minimizing power consumption. 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 I ✕ R loss of the MOSFET on-resistance, and quiescent current overhead. The theoretical best efficiency of a linear amplifier is 78%; however, that efficiency is only exhibited at peak output powers. Under normal operating levels (typical music reproduction levels), efficiency falls below 30%, whereas the MAX9700 still exhibits >90% efficiencies under the same conditions (Figure 5). Idle Mode is a trademark of Maxim Integrated Products. 10 ______________________________________________________________________________________ 1.2W, Low-EMI, Filterless, Class D Audio Amplifier MAX9700 VIN = 0V 50.0 AMPLITUDE (dBμV/m) 45.0 40.0 35.0 30.0 OUT- 25.0 20.0 15.0 10.0 30.0 OUT+ 60.0 80.0 100.0 120.0 140.0 160.0 180.0 200.0 220.0 240.0 260.0 280.0 300.0 FREQUENCY (MHz) VOUT+ - VOUT- = 0V Figure 4. MAX9700 Outputs with No Input Signal Figure 3. MAX9700 EMI Spectrum Shutdown The MAX9700 has a shutdown mode that reduces power consumption and extends battery life. Driving SHDN low places the MAX9700 in a low-power (0.1µA) shutdown mode. Connect SHDN to VDD for normal operation. The MAX9700 features comprehensive click-and-pop suppression that eliminates audible transients on startup and shutdown. While in shutdown, the H-bridge is in a high-impedance state. During startup or power-up, the input amplifiers are muted and an internal loop sets the modulator bias voltages to the correct levels, preventing clicks and pops when the H-bridge is subsequently enabled. For 35ms following startup, a soft-start function gradually unmutes the input amplifiers. Applications Information 90 80 EFFICIENCY (%) Click-and-Pop Suppression EFFICIENCY vs. OUTPUT POWER 100 MAX9700 70 60 50 CLASS AB 40 30 VDD = 3.3V f = 1kHz RL - 8Ω 20 10 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 OUTPUT POWER (W) Figure 5. MAX9700 Efficiency vs. Class AB Efficiency Filterless Operation Traditional class D amplifiers require an output filter to recover the audio signal from the amplifier’s output. The filters add cost, increase the solution size of the amplifier, and can decrease efficiency. The traditional PWM scheme uses large differential output swings (2 x VDD peak-to-peak) and causes large ripple currents. Any parasitic resistance in the filter components results in a loss of power, lowering the efficiency. The MAX9700 does not require an output filter. The device relies on the inherent inductance of the speaker coil and the natural filtering of both the speaker and the human ear to recover the audio component of the square-wave output. Eliminating the output filter results in a smaller, less costly, more efficient solution. Because the frequency of the MAX9700 output is well beyond the bandwidth of most speakers, voice coil movement due to the square-wave frequency is very small. Although this movement is small, a speaker not designed to handle the additional power can be damaged. For optimum results, use a speaker with a series inductance >10µH. Typical 8Ω speakers exhibit series inductances in the 20µH to 100µH range. Power-Conversion Efficiency Unlike a class AB amplifier, the output offset voltage of a class D amplifier does not noticeably increase quiescent current draw when a load is applied. This is due to ______________________________________________________________________________________ 11 MAX9700 1.2W, Low-EMI, Filterless, Class D Audio Amplifier the power conversion of the class D amplifier. For example, an 8mV DC offset across an 8Ω load results in 1mA extra current consumption in a class AB device. In the class D case, an 8mV offset into 8Ω equates to an additional power drain of 8µW. Due to the high efficiency of the class D amplifier, this represents an additional quiescent-current draw of 8µW/(VDD/100η), which is on the order of a few microamps. 1μF SINGLE-ENDED AUDIO INPUT IN+ MAX9700 IN1μF Input Amplifier Differential Input The MAX9700 features a differential input structure, making it compatible with many CODECs, and offering improved noise immunity over a single-ended input amplifier. In devices such as cellular phones, high-frequency signals from the RF transmitter can be picked up by the amplifier’s input traces. The signals appear at the amplifier’s inputs as common-mode noise. A differential input amplifier amplifies the difference of the two inputs; any signal common to both inputs is canceled. Single-Ended Input The MAX9700 can be configured as a single-ended input amplifier by capacitively coupling either input to GND and driving the other input (Figure 6). DC-Coupled Input The input amplifier can accept DC-coupled inputs that are biased within the amplifier’s common-mode range (see the Typical Operating Characteristics). DC coupling eliminates the input-coupling capacitors, reducing component count to potentially one external component (see the System Diagram). However, the low-frequency rejection of the capacitors is lost, allowing low-frequency signals to feedthrough to the load. Component Selection Input Filter An input capacitor, CIN, in conjunction with the input impedance of the MAX9700 forms a highpass filter that removes the DC bias from an incoming signal. The ACcoupling capacitor allows the amplifier to bias the signal to an optimum DC level. Assuming zero source impedance, the -3dB point of the highpass filter is given by: f−3dB = 1 2πRINCIN Choose CIN 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 12 Figure 6. Single-Ended Input whose dielectrics have low-voltage coefficients, such as tantalum or aluminum electrolytic. Capacitors with high-voltage coefficients, such as ceramics, may result in increased distortion at low frequencies. 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 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 150Hz. 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. Output Filter The MAX9700 does not require an output filter. The device passes FCC emissions standards with 100mm of unshielded speaker cables. However, output filtering can be used if a design is failing radiated emissions due to board layout or cable length, or the circuit is near EMI-sensitive devices. Use an LC filter when radiated emissions are a concern, or when long leads are used to connect the amplifier to the speaker. Supply Bypassing/Layout Proper power-supply bypassing ensures low-distortion operation. For optimum performance, bypass VDD to GND and PVDD to PGND with separate 0.1µF capacitors as close to each pin as possible. A low-impedance, high-current power-supply connection to PVDD is assumed. Additional bulk capacitance should be added as required depending on the application and power-supply characteristics. GND and PGND should be star connected to system ground. Refer to the MAX9700 evaluation kit for layout guidance. ______________________________________________________________________________________ 1.2W, Low-EMI, Filterless, Class D Audio Amplifier 1μF RIGHT-CHANNEL DIFFERENTIAL AUDIO INPUT VDD PVDD IN+ MAX9700 OUT+ IN- OUTSYNC Designing with Volume Control The MAX9700 can easily be driven by single-ended sources (Figure 6), but extra care is needed if the source impedance “seen” by each differential input is unbalanced, such as the case in Figure 10a, where the MAX9700 is used with an audio taper potentiometer acting as a volume control. Functionally, this configuration works well, but can suffer from click-pop transients at power-up (or coming out of SHDN) depending on the volume-control setting. As shown, the click-pop performance is fine for either max or min volume, but worsens at other settings. 1μF LEFT-CHANNEL DIFFERENTIAL AUDIO INPUT VDD PVDD IN+ MAX9700 OUT+ IN- OUTSYNC Figure 7. Master-Slave Stereo Configuration TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER CROSSTALK vs. FREQUENCY 0 100 VDD = 3.3V f = 1kHz RL = 8Ω SLAVE DEVICE CROSSTALK (dB) THD+N (%) 10 VDD = 3.3V RL = 8Ω f = 1kHz VIN = 500mVP-P -20 1 0.1 -40 MASTER-TO-SLAVE -60 -80 -100 0.01 SLAVE-TO-MASTER -120 0.001 0 0.1 0.2 0.3 OUTPUT POWER (W) Figure 8. Master-Slave THD+N 0.4 0.5 10 100 1k 10k 100k FREQUENCY (Hz) Figure 9. Master-Slave Crosstalk ______________________________________________________________________________________ 13 MAX9700 Stereo Configuration Two MAX9700s can be configured as a stereo amplifier (Figure 7). Device U1 is the master amplifier; its unfiltered output drives the SYNC input of the slave device (U2), synchronizing the switching frequencies of the two devices. Synchronizing two MAX9700s ensures that no beat frequencies occur within the audio spectrum. This configuration works when the master device is in either FFM or SSM mode. There is excellent THD+N performance and minimal crosstalk between devices due to the SYNC connection (Figures 8 and 9). U2 locks onto only the frequency present at SYNC, not the pulse width. The internal feedback loop of device U2 ensures that the audio component of U1’s output is rejected. VDD MAX9700 1.2W, Low-EMI, Filterless, Class D Audio Amplifier One solution is the configuration shown in Figure 10b. The potentiometer is connected between the differential inputs, and these “see” identical RC paths when the device powers up. The variable resistive element appears between the two inputs, meaning the setting affects both inputs the same way. The potentiometer is audio taper, as in Figure 10a. This significantly improves transient performance on power-up or release from SHDN. A similar approach can be applied when the MAX9700 is driven differentially and a volume control is required. UCSP Applications Information For the latest application details on UCSP construction, dimensions, tape carrier information, PC board techniques, bump-pad layout, and recommended reflow temperature profile, as well as the latest information on reliability testing results, refer to the Application Note: UCSP—A Wafer-Level Chip-Scale Package available on Maxim’s website at www.maxim-ic.com/ucsp. 1μF CW 22kΩ 1μF IN- 50kΩ IN- CW 50kΩ MAX9700 1μF IN+ MAX9700 IN+ 22kΩ 1μF Figure 10b. Improved Single-Ended Drive of MAX9700 Plus Volume Figure 10a. Single-Ended Drive of MAX9700 Plus Volume Selector Guide Ordering Information (continued) PART TEMP RANGE PINPACKAGE TOP MARK PIN-PACKAGE GAIN (dB) MAX9700AETB 10 TDFN-EP* 6 ACN MAX9700AEUB 10 µMAX 6 PART MAX9700CETB -40oC to +85oC 10 TDFN-EP* MAX9700CEUB -40oC to +85oC 10 µMAX — MAX9700AEBC-T MAX9700CEBC-T -40oC to +85oC 12 UCSP — MAX9700BETB MAX9700DETB -40oC to +85oC 10 TDFN-EP* ACO MAX9700BEUB 10 µMAX 12 MAX9700DEUB -40oC to +85oC 10 µMAX — MAX9700BEBC-T 12 UCSP 12 MAX9700DEBC-T -40oC to +85oC 12 UCSP — MAX9700CETB 10 TDFN-EP* 15.6 *EP = Exposed pad. 12 UCSP 6 10 TDFN-EP* 12 MAX9700CEUB 10 µMAX 15.6 MAX9700CEBC-T 12 UCSP 15.6 10 TDFN-EP* 20 MAX9700DETB MAX9700DEUB 10 µMAX 20 MAX9700DEBC-T 12 UCSP 20 *EP = Exposed pad. 14 ______________________________________________________________________________________ 1.2W, Low-EMI, Filterless, Class D Audio Amplifier VDD 1μF VDD VDD 0.1μF AUX_IN PVDD IN+ OUT 2.2kΩ OUT+ IN- OUT- SHDN SYNC CODEC/ BASEBAND PROCESSOR OUT BIAS MAX9700 2.2kΩ MAX4063 0.1μF IN+ VDD IN0.1μF 1μF VDD SHDN 1μF INL OUTL 1μF MAX9722 INR μCONTROLLER OUTR PVSS SVSS C1P CIN 1μF 1μF Pin Configurations (continued) TOP VIEW (BUMP SIDE DOWN) 1 TRANSISTOR COUNT: 3595 PROCESS: BiCMOS MAX9700 2 VDD Chip Information 3 4 SYNC OUT+ PGND PVDD A IN+ SHDN IN- GND B OUT- C UCSP ______________________________________________________________________________________ 15 MAX9700 System Diagram Package Information For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. PACKAGE TYPE PACKAGE CODE DOCUMENT NO. 12 UCSP B12-11 21-0104 10 TDFN-EP T1033-1 21-0137 10 µMAX U10-2 21-0061 12L, UCSP 4x3.EPS MAX9700 1.2W, Low-EMI, Filterless, Class D Audio Amplifier PACKAGE OUTLINE, 4x3 UCSP 21-0104 16 ______________________________________________________________________________________ F 1 1 1.2W, Low-EMI, Filterless, Class D Audio Amplifier 6, 8, &10L, DFN THIN.EPS ______________________________________________________________________________________ 17 MAX9700 Package Information (continued) For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. MAX9700 1.2W, Low-EMI, Filterless, Class D Audio Amplifier Package Information (continued) For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. 18 COMMON DIMENSIONS PACKAGE VARIATIONS SYMBOL MIN. MAX. PKG. CODE N D2 E2 e JEDEC SPEC b [(N/2)-1] x e A 0.70 0.80 T633-2 6 1.50–0.10 2.30–0.10 0.95 BSC MO229 / WEEA 0.40–0.05 1.90 REF D 2.90 3.10 T833-2 8 1.50–0.10 2.30–0.10 0.65 BSC MO229 / WEEC 0.30–0.05 1.95 REF E 2.90 3.10 T833-3 8 1.50–0.10 2.30–0.10 0.65 BSC MO229 / WEEC 0.30–0.05 1.95 REF A1 0.00 0.05 T1033-1 10 1.50–0.10 2.30–0.10 0.50 BSC MO229 / WEED-3 0.25–0.05 2.00 REF L 0.20 0.40 T1033-2 10 1.50–0.10 2.30–0.10 0.50 BSC MO229 / WEED-3 0.25–0.05 2.00 REF k 0.25 MIN. T1433-1 14 1.70–0.10 2.30–0.10 0.40 BSC ---- 0.20–0.05 2.40 REF A2 0.20 REF. T1433-2 14 1.70–0.10 2.30–0.10 0.40 BSC ---- 0.20–0.05 2.40 REF ______________________________________________________________________________________ 1.2W, Low-EMI, Filterless, Class D Audio Amplifier 10LUMAX.EPS α α ______________________________________________________________________________________ 19 MAX9700 Package Information (continued) For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. MAX9700 1.2W, Low-EMI, Filterless, Class D Audio Amplifier Revision History REVISION NUMBER REVISION DATE 0 10/03 Initial release 1 6/04 Changes made to TOCs and specs 2 10/08 Addition of EP information to pin description table DESCRIPTION PAGES CHANGED — 3–8, 14, 15 1, 2, 3, 8, 14 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 20 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2008 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.