19-3976; Rev 0; 1/06 1.8W, Filterless, Ultra-Low EMI, Stereo Class D Audio Power Amplifier The MAX9773 3rd-generation, ultra-low EMI, stereo, Class D audio power amplifier provides Class AB performance with Class D efficiency. The MAX9773 delivers 1.8W per channel into a 4 load, and offers efficiencies above 90%. Active emissions limiting (AEL) circuitry greatly reduces EMI by actively controlling the output FET gate transitions under all possible transient conditions. AEL controls high-frequency emissions resulting from conventional Class D free-wheeling behavior in the presence of an inductive load. Zerodead-time (ZDT) technology maintains state-of-the-art efficiency and THD+N performance by allowing the output FETs to switch simultaneously without cross conduction. A spread-spectrum modulation scheme eliminates the need for output filtering found in traditional Class D devices. These design concepts reduce component count and extend battery life. The MAX9773 offers two modulation schemes: a fixedfrequency (FFM) mode, and a spread-spectrum (SSM) mode that reduces EMI-radiated emissions. The MAX9773 oscillator can be synchronized to an external clock through the SYNC input, allowing synchronization of multiple Maxim Class D amplifiers. The sync output (SYNC_OUT) can be used for a master-slave application where more channels are required. The MAX9773 features a fully differential architecture, a full bridge-tied load (BTL) output, and comprehensive click-and-pop suppression. The device features internally set gains of 12dB, 15.6dB, 20dB, and 26dB selected through two gain-select inputs, further reducing external component count. The MAX9773 features high 80dB PSRR, less than 0.1% THD+N, and SNR in excess of 88dB. Short-circuit and thermal-overload protection prevent the device from being damaged during a fault condition. The MAX9773 is available in 24-pin thin QFN-EP (4mm x 4mm x 0.8mm), and 20-bump UCSPTM (2mm x 2.5mm x 0.6mm) packages. The MAX9773 is specified over the extended -40C to +85C temperature range. Applications Cellular/Multimedia Phones Features Filterless Amplifier Passes FCC-Radiation Emissions Standards with 6in of Cable Unique Spread-Spectrum Mode and Active Emissions Limiting Achieves Better than 15dB Margin Under FCC Limit Zero Dead Time (ZDT) H-Bridge Maintains Good THD+N Performance Single-Supply Operation (2.5V to 5.5V) Stereo Output (4, VDD = 5V, THD+N = 1%, POUT = 1.8W) No LC Output Filter Required 85% Efficiency (RL = 8, PO = 600mW) Less Than 0.1% THD+N High 80dB PSRR Fully Differential Inputs Integrated Click-and-Pop Suppression Low-Power Shutdown Mode (0.1A) Short-Circuit and Thermal-Overload Protection Pin-for-Pin Compatible with the MAX9701 Available in Thermally Efficient, Space-Saving Packages 24-Pin TQFN-EP (4mm x 4mm x 0.8mm) 20-Bump UCSP (2mm x 2.5mm x 0.6mm) Ordering Information PART TEMP RANGE PINPACKAGE PKG CODE MAX9773EBP-T -40C to +85C 20 UCSP-20 B20-1 MAX9773ETG+ -40C to +85C 24 TQFN-EP* T2444-4 +Denotes lead-free package. *EP = Exposed paddle. Block Diagram VDD MAX9773 INR+ RIGHT MODULATOR AND H-BRIDGE INR- GAIN1 GAIN2 GAIN Notebooks Handheld Gaming Consoles MP3 Players Pin Configurations and Gain Selection appear at end of data sheet. INL+ LEFT MODULATOR AND H-BRIDGE INL- SYNC OSCILLATOR SYNC_OUT UCSP is a trademark of Maxim Integrated Products, Inc. ________________________________________________________________ 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 MAX9773 General Description MAX9773 1.8W, Filterless, Ultra-Low EMI, Stereo Class D Audio Power Amplifier ABSOLUTE MAXIMUM RATINGS Duration of Short Circuit Between OUT+ and OUT- ......Continuous Continuous Power Dissipation (TA = +70C) 20-Bump UCSP (derate 10mW/C above +70C) ...........800mW 24-Pin Thin QFN (derate 20.8mW/C above +70C) ..1666.7mW Junction Temperature ......................................................+150C Operating Temperature Range ...........................-40C to +85C Storage Temperature Range .............................-65C to +150C Bump Temperature (soldering) Reflow............................+235C Lead Temperature (soldering, 10s) .................................+300C VDD to GND..............................................................................6V VDD to PVDD ..........................................................-0.3V to +0.3V 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 In/Out of PVDD, PGND, OUT_ .........800mA Continuous Input Current (all other pins)..........................20mA Duration of OUT_ Short Circuit to VDD/GND/PVDD/PGND...........................................Continuous 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 = VPVDD = VSHDN = 3.3V, VGND = VPGND = 0V, SYNC = 0V (FFM), gain = 12dB (GAIN1 = 1, GAIN2 = 1), RL connected between OUT+ and OUT-, RL = , TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) (Notes 1, 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 5.5 V 5.5 7.5 mA 0.1 10 GENERAL Supply Voltage Range VDD Inferred from PSRR test Quiescent Current IDD Per channel Shutdown Current ISHDN Common-Mode Rejection Ratio CMRR Input Bias Voltage VBIAS Turn-On Time tON Output Offset Voltage VOS 2.6 fIN = 1kHz 66 1.125 PSRR 10 TA = +25oC VDD = 2.5V to 5.5V, VIN = 0V, TA = +25 C 59 TMIN < TA < TMAX 56 100mVP-P ripple, VIN = 0V Output Power (Note 3) Total Harmonic Distortion Plus Noise (Note 3) POUT THD+N THD+N = 1%, TA = +25oC fRIPPLE = 217Hz VDD = 3.3V VDD = 5V SNR Oscillator Frequency fOSC 50 RL = 8 500 RL = 4 750 RL = 8 1300 RL = 4 1800 0.04 0.08 FFM SSM 86 88.5 SSM 88.5 SYNC Frequency Lock Range 2 dB 950 1100 1250 SYNC = unconnected, TA = +25oC 1200 1400 1600 kHz 1200 60 tMIN fSYNC % SYNC = GND, TA = +25 C SYNC = VDD, TA = +25oC Minimum On-Time mW 86 FFM o mV dB RL = 4 (POUT = 600mW), f = 1kHz A-weighted 50 80 RL = 8 (POUT = 400mW), f = 1kHz VOUT = 1VRMS V ms 72 fRIPPLE = 20kHz BW = 22Hz to 22kHz Signal-to-Noise Ratio 1.375 80 o Power-Supply Rejection Ratio 1.25 A dB 200 1000 _______________________________________________________________________________________ ns 2000 kHz 1.8W, Filterless, Ultra-Low EMI, Stereo Class D Audio Power Amplifier (VDD = VPVDD = VSHDN = 3.3V, VGND = VPGND = 0V, SYNC = 0V (FFM), gain = 12dB (GAIN1 = 1, GAIN2 = 1), RL connected between OUT+ and OUT-, RL = , TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) (Notes 1, 2) PARAMETER SYNC_OUT Capacitance Drive Capacitive Drive SYMBOL CL Click-and-Pop Level KCP Efficiency CONDITIONS MIN CSYNC_OUT RIN Gain AV Bridge-tied capacitance 200 Single ended 400 Peak reading, A-weighted, 32 samples per second (Note 4) Into shutdown -50 Out of shutdown -50 POUT = 600mW per channel, fIN = 1kHz, RL = 8 10 pF dBV % 16 GAIN1 = 1, GAIN2 = 0 30 GAIN1 = 0, GAIN2 = 1 45 GAIN1 = 1, GAIN2 = 1 60 GAIN1 = 0, GAIN2 = 0 26 GAIN1 = 1, GAIN2 = 0 20 GAIN1 = 0, GAIN2 = 1 15.6 GAIN1 = 1, GAIN2 = 1 12 L to R, R to L, f = 10kHz, RL = 8, POUT = 300mW UNITS pF 85 Channel-to-Channel Gain Tracking Crosstalk MAX 100 GAIN1 = 0, GAIN2 = 0 Input Resistance TYP k dB 1 % 80 dB DIGITAL INPUTS (SHDN, SYNC, GAIN1, GAIN2) Input-Voltage High VINH Input-Voltage Low VINL 2 V Input Leakage Current (SHDN, GAIN1, GAIN2) VSYNC = GND, normal operation Input Leakage Current (SYNC) -15 VSYNC = VDD, normal operation 0.8 V 1 A -7 12 25 A DIGITAL OUTPUTS (SYNC_OUT) Output-Voltage High VOH IOH = 3mA, VDD = 3.3V Output-Voltage Low VOL IOL = 3mA 2.4 V 0.4 V 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 = 4, L = 33H. For RL = 8, L = 68H. Note 3: When driving speakers below 4 with large signals, exercise care to avoid violating the absolute maximum rating for continuous output current. Note 4: Testing performed with 8 resistive load in series with 68H inductive load connected across the BTL output. Mode transitions are controlled by SHDN. KCP level is calculated as: 20 x log[(peak voltage during mode transition, no input signal)]. Units are expressed in dBV. _______________________________________________________________________________________ 3 MAX9773 ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (VDD = VPVDD = VSHDN = 3.3V, VGND = VPGND = 0V, SYNC = VDD (SSM), gain = 12dB (GAIN1 = 1, GAIN2 = 1)). VDD = 5V RL = 4 VDD = 5V RL = 8 10 1 1 VDD = 3.3V RL = 4 1 0.1 OUTPUT POWER = 600mW THD+N (%) THD+N (%) THD+N (%) OUTPUT POWER = 100mW OUTPUT POWER = 100mW OUTPUT POWER = 250mW 0.1 OUTPUT POWER = 300mW 0.1 OUTPUT POWER = 100mW OUTPUT POWER = 500mW 0.01 0.01 MAX9773 toc03 10 MAX9773 toc01 10 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY MAX9773 toc02 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY OUTPUT POWER = 300mW 0.01 OUTPUT POWER = 600mW 0.001 0.001 10 100 10k 100k 0.001 10 100 1k 10k 100k 10 10k FREQUENCY (Hz) TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER VDD = 5V RL = 8 POUT = 800mW VDD = 5V RL = 4 10 1 OUTPUT POWER = 400mW THD+N (%) THD+N (%) FFM 0.1 0.1 0.01 0.1 10k 100k fIN = 20Hz fIN = 20kHz 0.001 0.001 0.001 1k fIN = 1kHz 0.01 OUTPUT POWER = 250mW 100 1 SSM 0.01 10 10 100 1k 10k 0 100k 0.5 1.0 1.5 2.0 FREQUENCY (Hz) FREQUENCY (Hz) OUTPUT POWER (W) TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER 1 fIN = 1kHz 0.1 1.0 0.1 0.01 0.01 0.6 0.9 1.2 OUTPUT POWER (W) 1.5 1.8 10 1 fIN = 1kHz 0.1 fIN = 20Hz 0.001 0.3 VDD = 3.3V RL = 8 0.01 fIN = 20kHz fIN = 1kHz fIN = 20kHz 0.001 100 2.5 MAX9773 toc09 fIN = 20Hz 10 THD+N (%) 10 VDD = 3.3V RL = 4 THD+N (%) VDD = 5V RL = 8 MAX9773 toc08 100 MAX9773 toc07 100 fIN = 20Hz 100k MAX9773 toc06 100 MAX9773 toc05 10 OUTPUT POWER = 100mW 4 1k FREQUENCY (Hz) VDD = 3.3V RL = 8 0 100 FREQUENCY (Hz) 1 THD+N (%) 1k MAX9773 toc04 10 THD+N (%) MAX9773 1.8W, Filterless, Ultra-Low EMI, Stereo Class D Audio Power Amplifier fIN = 20kHz 0.001 0 0.2 0.4 0.6 OUTPUT POWER (W) 0.8 1.0 0 0.2 0.4 OUTPUT POWER (W) _______________________________________________________________________________________ 0.6 0.8 1.8W, Filterless, Ultra-Low EMI, Stereo Class D Audio Power Amplifier EFFICIENCY vs. OUTPUT POWER FFM 0.1 MAX9773 toc11 80 70 60 90 RL = 4 50 40 30 0.01 10 0.001 1.2 1.6 2.0 0.5 OUTPUT POWER (W) 1.5 2.0 2.5 3.0 0 THD+N = 10% 1.5 1.0 THD+N = 1% RL = 8 fIN = 1kHz 3.0 1.0 4.0 4.5 SUPPLY VOLTAGE (V) 5.0 5.5 1.0 1.2 2.0 THD+N = 10% 1.5 1.0 THD+N = 1% 0 3.5 0.8 VDD = 5V, f = 1kHz, ZLOAD = 33H IN SERIES WITH RL 2.5 0.5 3.0 0.6 OUTPUT POWER vs. LOAD RESISTANCE THD+N = 10% 0.5 2.5 0.4 1.5 0.5 0 0.2 OUTPUT POWER (W) OUTPUT POWER vs. SUPPLY VOLTAGE OUTPUT POWER (W) OUTPUT POWER (W) 2.0 1.0 2.0 MAX9773 toc13 RL = 4 fIN = 1kHz 2.5 VDD = 3.3V fIN = 1kHz OUTPUT POWER PER CHANNEL OUTPUT POWER (W) OUTPUT POWER vs. SUPPLY VOLTAGE 3.0 40 0 0 OUTPUT POWER (W) 0.8 RL = 4 50 10 MAX9773 toc14 0.4 60 20 0 0 70 30 VDD = 5V fIN = 1kHz OUTPUT POWER PER CHANNEL 20 SSM RL = 8 80 MAX9773 toc15 1 100 EFFICIENCY (%) THD+N (%) 10 RL = 8 90 EFFICIENCY (%) VDD = 5V RL = 8 fIN = 1kHz EFFICIENCY vs. OUTPUT POWER 100 MAX9773 toc10 100 MAX9773 toc12 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER 2.5 3.0 3.5 4.0 4.5 SUPPLY VOLTAGE (V) 5.0 5.5 THD+N = 1% 0 1 10 100 LOAD RESISTANCE () _______________________________________________________________________________________ 5 MAX9773 Typical Operating Characteristics (continued) (VDD = VPVDD = VSHDN = 3.3V, VGND = VPGND = 0V, SYNC = VDD (SSM), gain = 12dB (GAIN1 = 1, GAIN2 = 1)). Typical Operating Characteristics (continued) (VDD = VPVDD = VSHDN = 3.3V, VGND = VPGND = 0V, SYNC = VDD (SSM), gain = 12dB (GAIN1 = 1, GAIN2 = 1)). POWER-SUPPLY REJECTION RATIO vs. FREQUENCY VRIPPLE = 100mVP-P RL = 8 -10 -20 70 -40 PSRR (dB) THD+N = 10% 0.6 -50 -60 0.4 THD+N = 1% 10 -80 20 -90 10 0 10 100 1k -70 CROSSTALK (dBV) CROSSTALK (dB) -60 RIGHT TO LEFT -90 -100 -110 LEFT TO RIGHT -120 -140 1k 10k fIN = 1kHz RL = 8 ONE CHANNEL DRIVEN -40 -50 -60 -70 -80 -90 -100 -110 -120 -130 100 100k -94 FREQUENCY (Hz) OUTPUT FREQUENCY SPECTRUM -34 -14 6 OUTPUT FREQUENCY SPECTRUM -60 -80 -100 -120 SSM MODE VOUT = -60dB f = 1kHz RL = 8 UNWEIGHTED -20 OUTPUT MAGNITUDE (dBV) OUTPUT MAGNITUDE (dBV) -54 0 MAX9773 toc21 FFM MODE VOUT = -60dBV f = 1kHz RL = 8 UNWEIGHTED -40 -74 INPUT AMPLITUDE (dB) 0 -20 1k CROSSTALK vs. INPUT AMPLITUDE 0 -10 -20 -30 MAX9773 toc19 POUT = 300mW RL = 8 10 100 FREQUENCY (Hz) CROSSTALK vs. FREQUENCY -40 -80 10 100k 10k FREQUENCY (Hz) LOAD RESISTANCE () -50 40 30 100 VDD = 5V 50 MAX9773 toc22 1 60 -70 -100 0 VDD = 3.3V 80 CMRR (dB) 0.8 VRIPPLE = 100mVP-P RL = 8 90 -30 0.2 -40 -60 -80 -100 -120 -140 -140 0 5 10 FREQUENCY (kHz) 6 100 MAX9773 toc20 1.0 0 MAX9773 toc17 VDD = 3.3V, f = 1kHz, ZLOAD = 33H IN SERIES WITH RL MAX9773 toc16 1.2 COMMON-MODE REJECTION RATIO vs. FREQUENCY 15 MAX9773 toc18 OUTPUT POWER vs. LOAD RESISTANCE OUTPUT POWER (W) MAX9773 1.8W, Filterless, Ultra-Low EMI, Stereo Class D Audio Power Amplifier 20 0 5 10 15 20 FREQUENCY (kHz) _______________________________________________________________________________________ 10k 100k 1.8W, Filterless, Ultra-Low EMI, Stereo Class D Audio Power Amplifier WIDEBAND OUTPUT SPECTRUM (FFM MODE) WIDEBAND OUTPUT SPECTRUM (SSM MODE (SPEAKER MODE)) -30 -40 -50 -60 -70 MAX9773 toc24 -20 -30 -40 -50 -60 -70 -80 -80 -90 -90 -100 -100 0.1 1 100 10 0.1 1 10 FREQUENCY (MHz) FREQUENCY (MHz) TURN-ON/TURN-OFF RESPONSE SUPPLY CURRENT vs. SUPPLY VOLTAGE MAX9773 toc25 100 20 MAX9773 toc26 OUTPUT AMPLITUDE (dBV) RL = 8, VDD = 5V INPUTS AC-GROUNDED -10 OUTPUT AMPLITUDE (dBV) RL = 8, VDD = 5V INPUTS AC-GROUNDED -20 0 MAX9773 toc23 0 -10 BOTH CHANNELS DRIVEN SHDN 17 MAX9773 DIFFERENTIAL OUTPUT SUPPLY CURRENT (mA) 2V/div 1V/div SSM 14 FFM 11 8 5 20ms/div 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 SUPPLY VOLTAGE (V) SHUTDOWN CURRENT vs. SUPPLY VOLTAGE SHUTDOWN CURRENT (A) MAX9773 toc27 0.16 0.14 0.12 0.10 0.08 0.06 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 SUPPLY VOLTAGE (V) _______________________________________________________________________________________ 7 MAX9773 Typical Operating Characteristics (continued) (VDD = VPVDD = VSHDN = 3.3V, VGND = VPGND = 0V, SYNC = VDD (SSM), gain = 12dB (GAIN1 = 1, GAIN2 = 1)). 1.8W, Filterless, Ultra-Low EMI, Stereo Class D Audio Power Amplifier MAX9773 Pin Description PIN TQFN UCSP 1 A2 2 8 B3 NAME FUNCTION SHDN Active-Low Shutdown. Connect to VDD for normal operation. SYNC Frequency Select and External Clock Input: SYNC = GND: Fixed-frequency mode with fS = 1100kHz. SYNC = Unconnected: Fixed-frequency mode with fS = 1400kHz. SYNC = VDD: Spread-spectrum mode with fS = 1200kHz 60kHz. SYNC = Clocked: Fixed-frequency mode with fS = external clock frequency. 3, 8, 11, 16 -- N.C. 4 A3 OUTL+ No Connection. Not internally connected. 5, 14 A4, D4 PVDD 6, 13 B4, C4 PGND Power Ground 7 A5 OUTL- Left-Channel Amplifier Output Negative Phase 9, 22 B1, B5 GND 10 C5 SYNC_OUT 12 D5 OUTR- Right-Channel Amplifier Output Negative Phase 15 D3 OUTR+ Right-Channel Amplifier Output Positive Phase 17 C3 GAIN1 Gain-Select Input 1 18 D2 GAIN2 19 D1 INR- 20 C2 INR+ Right-Channel Noninverting Input 21 C1 VDD Analog Power Supply. Connect to PVDD. Bypass with a 10F capacitor to GND. 23 B2 INL+ Left-Channel Noninverting Input 24 A1 INL- Left-Channel Inverting Input EP -- EP Left-Channel Amplifier Output Positive Phase H-Bridge Power Supply. Connect to VDD. Bypass with a 0.1F capacitor to PGND. Analog Ground Clock Signal Output Gain-Select Input 2 Right-Channel Inverting Input Exposed Pad. Connect the exposed thermal pad to the GND plane (see the Supply Bypassing, Layout, and Grounding section). _______________________________________________________________________________________ 1.8W, Filterless, Ultra-Low EMI, Stereo Class D Audio Power Amplifier VDD 0.1F 10F* VDD INL+ 470nF CLASS D MODULATOR AND H-BRIDGE INL- INR+ RIN INR- RIN 470nF VBIAS RIN RIN 470nF SYNC_OUT OSCILLATOR AND SAWTOOTH SYNC 470nF PVDD CLASS D MODULATOR AND H-BRIDGE VBIAS OUTL+ OUTL- OUTR+ OUTR- VBIAS BIAS GENERATOR GAIN1 GAIN2 GAIN CONTROL MAX9773 SHDN GND PGND *BULK CAPACITANCE. _______________________________________________________________________________________ 9 MAX9773 Functional Diagram MAX9773 1.8W, Filterless, Ultra-Low EMI, Stereo Class D Audio Power Amplifier tSW VIN- VIN+ OUT- OUT+ tON(MIN) VOUT+ - VOUT- Figure 1. MAX9773 Outputs with an Input Signal Applied Detailed Description The MAX9773 ultra-low EMI, filterless, stereo Class D audio power amplifier incorporates several improvements to switch-mode amplifier topology. The MAX9773 features output-driver AEL circuitry to reduce EMI. Zero dead time technology maintains state-of-the art efficiency and THD+N performance by allowing the output FETs to switch simultaneously without cross conduction. The MAX9773 offers Class AB performance with Class D efficiency, while occupying minimal board space. A unique, filterless modulation scheme, synchronizable switching frequency, and spread-spectrum switching 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 10 input-coupling capacitors. The inputs can also be configured to accept a single-ended input signal. Comparators monitor the MAX9773 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 while the other output pulse duration remains the same. This causes the net voltage across the speaker (VOUT+ - VOUT-) to change. The minimum-width pulse helps the device to achieve high levels of linearity. ______________________________________________________________________________________ 1.8W, Filterless, Ultra-Low EMI, Stereo Class D Audio Power Amplifier tSW tSW MAX9773 tSW tSW VIN_- VIN_+ OUT_- OUT_+ tON(MIN) VOUT_+ - VOUT_- Figure 2. MAX9773 Outputs with an Input Signal Applied (SSM Mode) Operating Modes Fixed-Frequency (FFM) Mode The MAX9773 features two fixed-frequency modes. Connect SYNC to GND to select a 1.1MHz switching frequency. Leave SYNC unconnected to select a 1.4MHz switching frequency. The frequency spectrum of the MAX9773 consists of the fundamental switching frequency and its associated harmonics (see the Wideband FFT graph in the Typical Operating Characteristics). Program the switching frequency so the harmonics do not fall within a sensitive frequency band (Table 1). Audio reproduction is not affected by changing the switching frequency. Table 1. Operating Modes SYNC MODE GND FFM with fOSC = 1100kHz Unconnected FFM with fOSC = 1400kHz VDD Clocked SSM with fOSC = 1200kHz 60kHz FFM with fOSC = external clock frequency ______________________________________________________________________________________ 11 the MAX9773 to be synchronized to another Maxim Class D amplifier operating in SSM mode. Spread-Spectrum (SSM) Mode The MAX9773 features a unique spread-spectrum mode that flattens the wideband spectral components, improving EMI emissions that may be radiated by the speaker and cables. This mode is enabled by connecting SYNC to VDD (Table 1). In SSM mode, the switching frequency varies randomly by 60kHz around the center frequency (1.2MHz). The modulation 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). A proprietary amplifier topology ensures this does not corrupt the noise floor in the audio bandwidth. SYNC_OUT SYNC_OUT allows several MAX9773s as well as other Class D amplifiers (such as the MAX9700) to be cascaded. The synchronized output minimizes interference due to clock intermodulation caused by the switching spread between single devices. Using SYNC_OUT, the modulation scheme remains the same and audio reproduction is not affected by changing the switching frequency. Filterless Modulation/Common-Mode Idle The MAX9773 uses Maxim's unique modulation scheme that eliminates the LC filter required by traditional Class D amplifiers, improving efficiency, reducing component count, conserving board space and system cost. Conventional Class D amplifiers output a 50% duty cycle, 180 out-of-phase 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, which increases power consumption especially when idling. When no signal is present at the input of the MAX9773, the amplifiers output an in-phase square wave as shown in Figure 4. Because the MAX9773 drives the speaker differentially, the two outputs cancel each other, resulting in no net idle mode voltage across the speaker, minimizing power consumption. Synchronous Switching Mode SYNC The SYNC input allows the MAX9773 to be synchronized to a user-defined 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 TTL clock signal between 1000kHz and 2000kHz to SYNC synchronizes the MAX9773. The period of the SYNC clock can be randomized, allowing 40 35 AMPLITUDE (dBV/m) MAX9773 1.8W, Filterless, Ultra-Low EMI, Stereo Class D Audio Power Amplifier 30 25 20 15 10 5 30 60 80 100 120 140 160 180 200 220 240 260 280 FREQUENCY (MHz) Figure 3. EMI Spectrum of MAX9773 with 6in of Twisted-Pair Speaker Cable with TDK Ferrite Beads MPZ1608S300A 12 ______________________________________________________________________________________ 300 1.8W, Filterless, Ultra-Low EMI, Stereo Class D Audio Power Amplifier MAX9773 EFFICIENCY vs. OUTPUT POWER VIN_ = 0V MAX9773 fig05 100 MAX9773 90 EFFICIENCY (%) 80 OUT_- 70 60 50 40 30 CLASS AB 20 OUT_+ VDD = 3.3V f = 1kHz RL - 8 10 0 0 VOUT_+ - VOUT_- = 0V 0.1 0.2 0.3 0.4 0.5 0.6 0.7 OUTPUT POWER (W) Figure 5. MAX9773 Efficiency vs. Class AB Efficiency Figure 4. MAX9773 Outputs with No Input Signal 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 I*R 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 powers. Under normal operating levels (typical music reproduction levels), efficiency falls below 30%, whereas the MAX9773 still exhibits >80% efficiencies under the same conditions (Figure 5). Shutdown The MAX9773 has a shutdown mode that reduces power consumption and extends battery life. Driving SHDN low places the MAX9773 in a low-power (0.1A) shutdown mode. Connect SHDN to VDD for normal operation. Click-and-Pop Suppression The MAX9773 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 80ms following startup, a soft-start function gradually unmutes the input amplifiers. 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 x VDD(P-P)) and causes large ripple currents. Any parasitic resistance in the filter components results in a loss of power, lowering the efficiency. The MAX9773 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 MAX9773 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 >10H. Typical 8 speakers, for portable audio applications, exhibit series inductances in the range of 20H to 100H. Output Offset 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 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 on the order of a few A. ______________________________________________________________________________________ 13 MAX9773 1.8W, Filterless, Ultra-Low EMI, Stereo Class D Audio Power Amplifier Selectable Gain Table 2. Gain Settings (VDD = 3.3V, THD+N = 10%) GAIN1 GAIN2 GAIN (dB) INPUT (VRMS) RL () POUT (mW) 0 0 +26 0.097699 4 950 4 950 1 0 +20 0.194936 0 1 +15.6 0.323513 4 950 1 1 12 0.489657 4 950 +26 0.114288 8 650 0 0 1 0 +20 0.228035 8 650 0 1 +15.6 0.378444 8 650 12 0.572798 8 650 1 1 The MAX9773 features four selectable gain settings, minimizing external component count. Gains of 12dB, 15.6dB, 20dB, and 26dB are set through gain-select inputs, GAIN1 and GAIN2. GAIN1 and GAIN2 can be hardwired or digitally controlled. Table 2 shows the suggested gain settings to attain a maximum output power from a given peak input voltage and given load at VDD = 3.3V and THD+N = 10%. Custom Gain Settings The MAX9773 can be set up with any gain setting by adding three external resistors per amplifier. Figure 6 shows the required circuit for setting up custom gain. Table 3 displays a list of the components to use for several gain settings. Table 3. Custom Gain Components GAIN_ SETTINGS 14 GAIN (dB) R1 () R2 () CIN (F) -- -- 1 -- 750 20k 1 +0.12/-0.07 GAIN TOLERANCE (dB) GAIN1 GAIN2 0 0 26 0 0 25 0 0 24 1k 10k 1.5 +0.14/-0.08 0 0 23 1k 6k 2.2 +0.13/-0.08 0 0 22 1.5k 6k 2.2 +0.16/-0.1 0 0 21 2k 6k 2 +0.19/-0.12 1 0 20 -- -- 1 -- 1 0 19 1.2k 30k 1 +0.1/-0.06 1 0 18 2k 20k 1 +0.15/-0.09 1 0 17 2k 10k 1.2 +0.12/-0.07 1 0 16 2.5k 10k 1.2 +0.15/-0.09 0 1 15 1k 40k 0.86 +0.06/-0.03 0 1 14 2.8k 40k 0.68 +0.15/-0.09 0 1 13 2.8k 20k 0.86 +0.14/-0.08 1 1 12 -- -- 1 -- 1 1 11 1.8k 40k 0.86 +0.08/-0.05 1 1 10 4k 40k 0.68 +0.15/-0.09 1 1 9 5k 30k 0.68 +0.17/-0.1 1 1 8 5k 20k 0.68 +0.15/-0.09 1 1 7 5.5k 16k 0.68 +0.15/-0.09 1 1 6 7k 16k 0.68 +0.17/-0.1 1 1 5 8k 14k 0.68 +0.17/-0.1 1 1 4 8k 12k 0.68 +0.16/-0.1 1 1 3 10k 12k 0.68 +0.17/-0.1 1 1 2 11k 10k 0.68 +0.16/-0.1 1 1 1 12k 10k 0.58 +0.16/-0.1 1 1 0 14k 10k 0.47 +0.17/-0.1 ______________________________________________________________________________________ 1.8W, Filterless, Ultra-Low EMI, Stereo Class D Audio Power Amplifier MAX9773 0.47F SINGLE-ENDED LEFT AUDIO INPUT INL+ OUTL+ MAX9773 CIN R1 INL+ 0.47F SINGLE-ENDED RIGHT AUDIO INPUT RIN INR+ MAX9773 INLR2 CIN R1 INL- 0.47F RIN INR- OUTLOUTR+ 0.47F OUTR- CIN GAIN2 R1 INR+ RIN GAIN1 SHDN R2 CIN R1 INR- 2.5V TO 5.5V RIN VDD PVDD 10F GND PGND 0.1F SYNC FFM MODE WITH fOSC = 1100kHz, GAIN = 15.6dB. Figure 6. Custom Gain Setting Figure 7. Single-Ended Input The internal input resistance, RIN, changes with each gain setting. The R1 resistors attenuate the gain and resistors R2 compensate for RIN's tolerance, which can be as high as 25%. CIN must be adjusted to compensate for the total change in input impedance or the lowfrequency roll-off point shifts. AC-coupling capacitor allows the amplifier to automatically bias the signal to an optimum DC level. Assuming zero-source impedance, the -3dB point of the highpass filter is given by: Input Amplifier Differential Input The MAX9773 features a differential input structure, making it compatible with many CODECs and offers 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 MAX9773 can be configured as a single-ended input amplifier by capacitively coupling either input to GND, and driving the other input (Figure 7). Component Selection Input Filter An input capacitor, C IN , in conjunction with the MAX9773 input impedance (RIN) forms a highpass filter that removes the DC bias from an incoming signal. The f-3dB = 1 2RINCIN 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 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. ______________________________________________________________________________________ 15 MAX9773 1.8W, Filterless, Ultra-Low EMI, Stereo Class D Audio Power Amplifier 5V CIN 2200pF 10F INL+ OUTL+ CIN 2200pF 8 MAX9773 INR+ OUTL- CIN 2200pF 10F INLOUTR+ CIN 2200pF 8 INROUTRSYNC SYNC_OUT R3 10k 5V R1 20k VDD R4 39k R2 20k SYNC C2 1nF 1F IN+ C1 0.01F 1.25V MAX4238 MAX9705 OUT+ 4 1F IN- OUT- NOTE: VALUES SHOWN ARE FOR A LOWPASS CUTOFF OF 2Hz AND A BASS GAIN OF -1V/V. FFM MODE WITH fOSC = 1100kHz. Figure 8. 2.1 Channel Application Circuit Output Filter The MAX9773 does not require an output filter. The device passes FCC emissions standards with 6in 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 if the circuit is near EMI-sensitive devices. Use a ferrite bead filter when radiated frequencies above 10MHz are of concern. Use an LC filter or a common-mode choke when radiated emissions below 10MHz are of concern, or when long leads (>6in) connect the amplifier to the speaker. 16 2.1 Channel Configuration The typical 2.1 channel application circuit (Figure 8) shows the MAX9773 configured as a mid/high-frequency amplifier and the MAX9705 configured as a mono bass amplifier. Input capacitors (CIN) set the highpass cutoff frequency according to the following equation: f= 1 2 x RIN x CIN where R IN is the typical input resistance of the MAX9773. The 10F capacitors on the output of the MAX9773 ensure a two-pole highpass filter. ______________________________________________________________________________________ 1.8W, Filterless, Ultra-Low EMI, Stereo Class D Audio Power Amplifier A VLP = -2 x R3 R1 where R1 = R2 and R3 = R1//R2. The cutoff frequency of the lowpass filter is set by the following equation: fLP = 1 x 2 1 C1 x C2 x R 3 x R4 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 PC board. Route all traces that carry switching transients away from GND and the traces/components in the audio signal path. Bypass VDD with a 0.1F capacitor to GND and PVDD with a 10F capacitor to PGND. Place the bypass capacitors as close to the MAX9773 as possible. Use large, low-resistance output traces. Current drawn from the outputs increases 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 MAX9773 to the air, decreasing the thermal impedance of the circuit. The MAX9773 thin QFN-EP package features an exposed thermal pad on its underside. This pad lowers the package's thermal impedance by providing a direct heat conduction path from the die to the PC board. Connect the exposed thermal pad to the GND plane. UCSP Applications Information For the latest application details on UCSP construction, dimensions, tape carrier information, printed circuit board techniques, bump-pad layout, and recommended reflow temperature profile, as well as the latest information on reliability testing results, refer to Application Note: UCSP--A Wafer-Level Chip-Scale Package available on Maxim's website at www.maxim-ic.com/ucsp. ______________________________________________________________________________________ 17 MAX9773 Low frequencies are summed through a two-pole lowpass filter and sent to the MAX9705 mono speaker amplifier. The passband gain of the lowpass filter is unity for in-phase stereo signals: 18 DVDD 10k APPLICATIONS PROCESSOR FM RECEIVER 10k 0.47F 0.47F DGND PGND AGND 2.2F C1N C1P HPS HPR GPIO REF OUTL OUTR HPL SVSS AVDD 1F SCL PVSS MAX9850 PVDD 1F SDA LRCLK SDIN BCLK MCLK INR INL DVDD 1F 1.8V TO 3.6V 0.47F 1F 0.47F 0.47F 0.47F 0.47F INL- INL+ INR- INR+ GAIN2 GAIN1 SYNC SHDN VDD GND MAX9773 PGND OUTL- OUTL+ OUTR- OUTR+ SYNC_OUT PVDD 4.2V BATTERY MAX9773 1.8W, Filterless, Ultra-Low EMI, Stereo Class D Audio Power Amplifier System Diagram ______________________________________________________________________________________ 1.8W, Filterless, Ultra-Low EMI, Stereo Class D Audio Power Amplifier TOP VIEW (BUMPS ON BOTTOM) GAIN2 GAIN1 N.C. OUTR+ PVDD PGND TOP VIEW 18 17 16 15 14 13 INR- 19 12 OUTR- INR+ 20 11 N.C. VDD 21 10 SYNC_OUT MAX9773 GND 22 INL+ 23 5 6 PVDD 4 PGND 3 N.C. 2 OUTL+ 1 SYNC + SHDN INL- 24 9 GND 8 N.C. 7 OUTL- MAX9773 1 2 3 4 5 A INL- SHDN OUTL+ PVDD OUTL- B GND INL+ SYNC PGND GND C VDD INR+ GAIN1 PGND SYNC _OUT D INR- GAIN2 OUTR+ PVDD OUTR- UCSP TQFN Gain Selection GAIN SELECTION GAIN1 = 0, GAIN2 = 0 GAIN (dB) Chip Information PROCESS: BiCMOS 26 GAIN1 = 1, GAIN2 = 0 20 GAIN1 = 0, GAIN2 = 1 15.6 GAIN1 = 1, GAIN2 = 1 12 ______________________________________________________________________________________ 19 MAX9773 Pin Configurations Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.) 24L QFN THIN.EPS MAX9773 1.8W, Filterless, Ultra-Low EMI, Stereo Class D Audio Power Amplifier PACKAGE OUTLINE, 12, 16, 20, 24, 28L THIN QFN, 4x4x0.8mm 21-0139 E 1 2 PACKAGE OUTLINE, 12, 16, 20, 24, 28L THIN QFN, 4x4x0.8mm 21-0139 E 2 2 MAX9773 Package Code: T2444-4 20 ______________________________________________________________________________________ 1.8W, Filterless, Ultra-Low EMI, Stereo Class D Audio Power Amplifier 5x4 UCSP.EPS PACKAGE OUTLINE, 5x4 UCSP 21-0095 I 1 1 MAX9773 Package Code: B20-1 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 21 (c) 2006 Maxim Integrated Products Heaney Printed USA is a registered trademark of Maxim Integrated Products, Inc. MAX9773 Package Information (continued) (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)