1.8W, Filterless, Ultra-Low EMI, Stereo Class D Audio Power Amplifier

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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 4Ω 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. Zero-dead- 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 fixed-frequency (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 UCSP™ (2mm x 2.5mm x 0.6mm) packages. The MAX9773 is specified over the extended -40°C to +85°C temperature range.

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