What the 25mW output means on the bench
The MAX9721AEBC-T is a Class AB stereo headphone amplifier from the DirectDrive® series, delivering 25mW per channel into a 16Ω load. That output level is typical for portable audio — enough to drive earbuds or low-impedance headphones to comfortable listening levels from a single-cell battery rail. The 0.9V to 1.8V supply range means this part runs directly off a Li-ion cell or a regulated 1.8V rail without a separate boost converter. The DirectDrive® charge-pump topology generates the negative supply internally, so you don't need DC-blocking capacitors on the output — a common failure point in conventional headphone amps.
Housed in a 12-ball UCSP (2.02 x 1.54 mm), this is a wafer-level chip-scale package. The 0.5mm ball pitch requires a well-controlled SMT process — the solder mask opening and stencil thickness matter more here than for a larger QFN.