Stereo Headphone Amplifier with BassMax, Volume Control, and Input Mux

Active: In Production.

The MAX9729 stereo DirectDrive® headphone amplifier features bass boost, volume control, an input mux, and an I²C/SMBus™-compatible serial interface. This makes the MAX9729 ideal for portable audio applications where space is at a premium and performance is essential. The MAX9729 operates from a single 1.8V to 3.6V, and uses Maxim's DirectDrive architecture, eliminating the need for large DC-blocking capacitors. The headphone amplifiers deliver 52mW into a 32Ω load, feature low 0.03% THD+N, and high 90dB PSRR. Maxim's industry-leading click-and-pop suppression circuitry reduces audible transients during power and shutdown cycles.

The BassMax feature boosts the bass response of the amplifier, improving audio reproduction for low-end headphones. The integrated volume control features 32 discrete volume levels along with a ramping function to ensure smooth transitions during shutdown cycles and input selection. The MAX9729's eight programmable maximum gain settings allow for a wide range of input signal levels. A 3:1 multiplexer/mixer allows the selection and summation of multiple stereo input signal sources. The MAX9729 also includes a dedicated BEEP input with independent attenuation control. BassMax, volume control, gain settings, and input selection are controlled using the I²C/SMBus-compatible serial interface. A low-power, 5µA shutdown mode is controlled through an external logic input or the serial interface.

The MAX9729 consumes only 4.8mA of supply current, provides short-circuit and thermal-overload protection, and is specified over the -40°C to +85°C extended temperature range. The MAX9729 is available in a space-saving 28-pin thin QFN package (5mm x 5mm x 0.8mm).

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