EVALUATION KIT AVAILABLE MAX9709 25W/50W, Filterless, Spread-Spectrum, Stereo/Mono, Class D Amplifier General Description The MAX9709 stereo/mono, Class D audio power amplifier delivers up to 2 x 25W into an 8Ω stereo mode and 1 x 50W into a 4Ω load in mono mode while offering up to 87% efficiency. The MAX9709 provides Class AB amplifier performance with the benefits of Class D efficiency, eliminating the need for a bulky heatsink and conserving power.
MAX9709 25W/50W, Filterless, Spread-Spectrum, Stereo/Mono, Class D Amplifier Absolute Maximum Ratings PVDD, VDD to PGND, GND..................................... -0.3 to +30V PVDD to VDD.........................................................-0.3V to +0.3V OUTR+, OUTR-, OUTL+, OUTL- to PGND, GND........................-0.3V to (PVDD + 0.3V) C1N to GND............................................-0.3V to (PVDD + 0.3V) C1P to GND........................... (PVDD - 0.3V) to (CPVDD + 0.3V) CPVDD to GND.......
MAX9709 25W/50W, Filterless, Spread-Spectrum, Stereo/Mono, Class D Amplifier Electrical Characteristics (continued) (PVDD = VDD = +20V, PGND = GND = 0V, CSS = 0.47µF, CREG = 0.01µF, C1 = 0.1µF, C2 = 1µF, RLOAD = ∞, MONO = low (stereo mode), SHDN = MUTE = high, G1 = low, G2 = high (AV = 22dB), FS1 = FS2 = high (SSM), SYNCIN = low. All load resistors (RL) are connected between OUT_+ and OUT_-, unless otherwise stated. TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.
MAX9709 25W/50W, Filterless, Spread-Spectrum, Stereo/Mono, Class D Amplifier Electrical Characteristics (continued) (PVDD = VDD = +20V, PGND = GND = 0V, CSS = 0.47µF, CREG = 0.01µF, C1 = 0.1µF, C2 = 1µF, RLOAD = ∞, MONO = low (stereo mode), SHDN = MUTE = high, G1 = low, G2 = high (AV = 22dB), FS1 = FS2 = high (SSM), SYNCIN = low. All load resistors (RL) are connected between OUT_+ and OUT_-, unless otherwise stated. TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.
MAX9709 25W/50W, Filterless, Spread-Spectrum, Stereo/Mono, Class D Amplifier Typical Operating Characteristics (PVDD = VDD = +20V, PGND = GND = 0V, CSS = 0.47µF, CREG = 0.01µF, C1 = 0.1µF, C2 = 1µF, RLOAD = 8Ω, SHDN = high, MONO = low, MUTE = high, G1 = low, G2 = high, FS1 = FS2 = high (SSM), SYNCIN = low. All load resistors (RL) are between OUT_+ and OUT_-, TA = +25°C, unless otherwise stated.) fIN = 1kHz THD+N (%) THD+N (%) POUT = 12W 0.1 0.1 15 20 25 30 35 0.
MAX9709 25W/50W, Filterless, Spread-Spectrum, Stereo/Mono, Class D Amplifier Typical Operating Characteristics (continued) (PVDD = VDD = +20V, PGND = GND = 0V, CSS = 0.47µF, CREG = 0.01µF, C1 = 0.1µF, C2 = 1µF, RLOAD = 8Ω, SHDN = high, MONO = low, MUTE = high, G1 = low, G2 = high, FS1 = FS2 = high (SSM), SYNCIN = low. All load resistors (RL) are between OUT_+ and OUT_-, TA = +25°C, unless otherwise stated.) RLOAD = 4Ω POUT = 22Ω 0.1 0.
MAX9709 25W/50W, Filterless, Spread-Spectrum, Stereo/Mono, Class D Amplifier Typical Operating Characteristics (continued) (PVDD = VDD = +20V, PGND = GND = 0V, CSS = 0.47µF, CREG = 0.01µF, C1 = 0.1µF, C2 = 1µF, RLOAD = 8Ω, SHDN = high, MONO = low, MUTE = high, G1 = low, G2 = high, FS1 = FS2 = high (SSM), SYNCIN = low. All load resistors (RL) are between OUT_+ and OUT_-, TA = +25°C, unless otherwise stated.
MAX9709 25W/50W, Filterless, Spread-Spectrum, Stereo/Mono, Class D Amplifier Typical Operating Characteristics (continued) (PVDD = VDD = +20V, PGND = GND = 0V, CSS = 0.47µF, CREG = 0.01µF, C1 = 0.1µF, C2 = 1µF, RLOAD = 8Ω, SHDN = high, MONO = low, MUTE = high, G1 = low, G2 = high, FS1 = FS2 = high (SSM), SYNCIN = low. All load resistors (RL) are between OUT_+ and OUT_-, TA = +25°C, unless otherwise stated.) POWER-SUPPLY REJECTION RATIO vs.
MAX9709 25W/50W, Filterless, Spread-Spectrum, Stereo/Mono, Class D Amplifier Pin Description (continued) PIN NAME FUNCTION 8 C1N Charge-Pump Flying Capacitor C1, Negative Terminal 9 C1P Charge-Pump Flying Capacitor C1, Positive Terminal 10 CPVDD 11 SYNCOUT Charge-Pump Power Supply. Bypass to PVDD with a 1µF capacitor as close to pin as possible.
MAX9709 25W/50W, Filterless, Spread-Spectrum, Stereo/Mono, Class D Amplifier Typical Application Circuits/Functional Diagrams VDD PVDD 0.
MAX9709 25W/50W, Filterless, Spread-Spectrum, Stereo/Mono, Class D Amplifier Typical Application Circuits/Functional Diagrams (continued) VDD PVDD 0.1µF 47µF* 0.
MAX9709 Detailed Description The MAX9709 filterless, Class D audio power amplifier features several improvements to switch mode amplifier technology. The MAX9709 is a two-channel, stereo amplifier with 25W output power on each channel. The amplifier can be configured to output 50W output power in mono mode. The device offers Class AB performance with Class D efficiency, while occupying minimal board space.
MAX9709 25W/50W, Filterless, Spread-Spectrum, Stereo/Mono, Class D Amplifier TEMP returns high once the junction temperature cools below the set threshold minus the thermal hysteresis. If TEMP is connected to either MUTE or SS, the audio output resumes. The temperature threshold is set by the TH0, TH1, and TH2 inputs as shown in Table 1. An RC filter may be used to eliminate any transient at the TEMP output as shown in Figure 3.
MAX9709 25W/50W, Filterless, Spread-Spectrum, Stereo/Mono, Class D Amplifier Linear Regulator (REG) The supply voltage range for the MAX9709 is from 10V to 22V to achieve high-output power. An internal linear regulator reduces this voltage to 6.3V for use with small-signal and digital circuitry that does not require high-voltage supply. Bypass a 0.01µF capacitor from REG to GND.
MAX9709 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. This prevents the unused device inputs from distorting the input signal. Mute the MAX9709 by driving MUTE low. Driving MUTE low turns off the Class D output stage, but does not affect the input bias levels of the MAX9709.
MAX9709 25W/50W, Filterless, Spread-Spectrum, Stereo/Mono, Class D Amplifier Auxiliary Heatsinking 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.
MAX9709 25W/50W, Filterless, Spread-Spectrum, Stereo/Mono, Class D Amplifier The circuit in Figure 6 uses inverting amplifiers for their ease in biasing. Note the phase labeling at the outputs has been reversed. The resistors should be 1% or better in tolerance and the capacitors 5% tolerance or better. Mismatch in the components can cause discrepancies between the nominal transfer function and actual performance.
MAX9709 25W/50W, Filterless, Spread-Spectrum, Stereo/Mono, Class D Amplifier R1 56.2kΩ R3 28kΩ C1 47nF R7 28kΩ 2 U1A MAX4478 R4 28kΩ RIGHT AUDIO INPUT R2, 56.2kΩ C2 47nF R5 56.2kΩ BIAS 3 6 U1B MAX4478 R8 56.2kΩ R10 28kΩ C5 47nF LEFT AUDIO INPUT R14 28kΩ BIAS 5 BIAS 10 R17 26.1kΩ R19 26.1kΩ R16 13kΩ BIAS 14 12 SUBWOOFER OUTPUT IS AC-COUPLED TO A MAX9709 CONFIGURED AS A MONO AMPLIFIER C9, 47nF R18 7.5kΩ C10 47nF LEFT AUDIO OUTPUT 13 U1D MAX4478 R15 26.1kΩ 8 R13, 56.
MAX9709 25W/50W, Filterless, Spread-Spectrum, Stereo/Mono, Class D Amplifier Pin Configurations OUTR- N.C. N.C. 51 50 OUTR- 52 OUTR+ OUTL- 53 OUTR+ OUTL- 54 PGND OUTL+ 55 PGND N.C. 56 OUTL+ N.C. TOP VIEW 49 48 47 46 45 44 43 + N.C. 1 42 N.C. PGND 2 41 PGND PGND 3 40 PGND PGND 4 39 PGND PVDD 5 38 PVDD PVDD 6 37 PVDD PVDD 7 C1N 8 C1P 9 MAX9709 CPVDD 10 36 PVDD 35 TH0 34 TH1 33 TH2 SYNCOUT 11 32 TEMP N.C.
MAX9709 25W/50W, Filterless, Spread-Spectrum, Stereo/Mono, Class D Amplifier Revision History REVISION NUMBER REVISION DATE PAGES CHANGED 0 9/05 Initial release 1 5/08 Removed TQFP package 2 5/14 Removed automotive reference from Applications section DESCRIPTION — 1, 2, 8–11, 20 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.
