The MAX9729 is a stereo DirectDrive™ headphone amplifier that features bass boost, volume control, an input mux, and an I2C/SMBus™-compatible serial interface. This makes the MAX9729 ideal for portable audio applica- tions 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 patented† DirectDrive architec- ture, eliminating the need for large DC-blocking capaci- tors. 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 sup- pression 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 o
The MAX9729 is a stereo DirectDrive™ headphone amplifier that operates from a single 1.8 V to 3.6 V supply and eliminates the need for large DC‑blocking capacitors. It delivers 52 mW into a 32 Ω load, features 0.03 % THD+N, 90 dB PSRR, 32‑step volume control, BassMax boost, and a 3:1 input multiplexer, all programmable via an I²C/SMBus‑compatible serial interface.
The device is supplied in a space‑saving 28‑pin thin QFN package (5 mm × 5 mm × 0.8 mm) and operates over an extended temperature range of –40 °C to +85 °C. It includes short‑circuit and thermal‑overload protection, a low‑power 5 µA shutdown mode, and a dedicated beep input with independent attenuation.
| THD+N | 0.03 % |
|---|---|
| Power‑Supply Rejection Ratio | 90 dB |
| Operating Temperature Range | –40 °C to +85 °C |
The amplifier achieves as low as 0.03 % total harmonic distortion plus noise.
Shutdown is controlled by an active‑low SHDN pin or via the I²C/SMBus interface.