The MAX9722AEUE+T is a Class AB stereo headphone amplifier from Analog Devices' DirectDrive® series, delivering 130mW per channel into a 32Ω load. That output level suits consumer headphones and in-ear monitors — enough volume headroom for most portable audio sources without the distortion of a Class D switching stage.
Supply range and DirectDrive — no DC-blocking caps needed
The DirectDrive architecture generates an internal negative supply, so the headphone output biases around ground — eliminating the pair of large DC-blocking electrolytic capacitors that conventional single-supply headphone amps need. That saves board area and avoids the low-frequency roll-off those capacitors introduce. The 16-TSSOP package (4.40mm body width) is compact enough for portable designs but still hand-solderable for prototyping.
Feature set for portable audio — depop, differential inputs, shutdown
The amplifier includes depop circuitry that suppresses the audible thump when the amplifier powers up or shuts down — a common complaint in battery-powered audio devices. Differential inputs reject common-mode noise picked up on the signal traces from the DAC or codec. Short-circuit and thermal protection prevent damage if the headphone jack is shorted or the output is driven into a low-impedance load. A shutdown pin drops quiescent current to near zero for battery conservation.