80mW, DirectDrive, Stereo Headphone Amplifier with Common-Mode Sense

The MAX4409 stereo headphone amplifier combines Maxim's DirectDrive® architecture and a common-mode sense input, which allows the amplifier to reject common-mode noise. Conventional headphone amplifiers require a bulky DC-blocking capacitor between the headphone and the amplifier. DirectDrive produces a ground-referenced output from a single supply, eliminating the need for large DC-blocking capacitors, which saves cost, board space, and component height. The common-mode voltage sensing corrects for any difference between SGND of the amplifier and the headphone return. This feature minimizes ground-loop noise when the HP socket is used as a line out connection to other grounded equipment, for example, a PC connected to a home hi-fi system.

The MAX4409 draws only 5mA of supply current, delivers up to 80mW per channel into a 16Ω load, and has a low 0.002% THD+N. A high 86dB power-supply rejection ratio allows this device to operate from noisy digital supplies without additional power-supply conditioning. The MAX4409 includes ±8kV ESD protection on the headphone outputs. Comprehensive click-and-pop circuitry eliminates audible clicks and pops on startup and shutdown. A low-power shutdown mode reduces supply current draw to only 6µA.

The MAX4409 operates from a single 1.8V to 3.6V supply, has short-circuit and thermal overload protection, and is specified over the extended -40°C to +85°C temperature range. The MAX4409 is available in a tiny 20-pin thin QFN (4mm x 4mm x 0.8mm) package.

Applications

* Cell Phones * Desktop PCs * MP3 Players * Notebook Computers * PDAs * Portable Audio Equipment * Tablet PCs

* No Bulky DC-Blocking Capacitors Required

* Ground-Referenced Outputs Eliminate DC-Bias Voltages on Headphone Ground Pin

* Common-Mode Voltage Sensing Eliminates Ground-Loop Noise

* 96dB CMRR

* No Degradation of Low-Frequency Response Due to Output Capacitors

* 80mW per Channel into 16Ω

* Low 0.002% THD+N

* High 86dB PSRR

* Integrated Click-and-Pop Suppression

* 1.8V to 3.6V Single-Supply Operation

* Low Quiescent Current

* Low-Power Shutdown Mode

* Short-Circuit and Thermal-Overload Protection

* ±8kV ESD-Protected Amplifier Outputs

* Available in a Space-Saving Package

* 20-Pin Thin QFN (4mm x 4mm x 0.8mm)