Output stage and load matching for the BOM
The MAX9763EUI delivers 3W per channel into a 3 Ohm load from a 5V rail — that 3 Ohm figure is the design target for portable speaker drivers where the DC resistance sits near 2.8 Ohm and the voice coil impedance bottoms out at resonance. At 4 Ohm the output power drops, but the Class AB linearity stays clean through the crossover region, which matters more for midrange clarity than raw SPL.
Supply rails and thermal envelope
The 4.5V to 5.5V supply window ties it to a single 5V rail — no dual supplies, no boost converter needed for the output swing. The exposed pad on the 28-TSSOP-EP is the thermal path: the die sits on the paddle, and the PCB copper plane under it sinks the Class AB quiescent heat. At 3W into 3 Ohm the efficiency is around 55-60%, so the other 40% dissipates as heat through that pad. A 1-square-inch copper pour on the bottom layer keeps the junction below 85°C at 25°C ambient.
Active lifecycle with a compliance catch
The catch is the RoHS non-compliant marking. This part uses lead-bearing solder terminations, which exempts it from RoHS for certain equipment categories but blocks it from EU consumer goods after July 2006 and from most new industrial designs targeting RoHS-10 compliance. If your BOM requires full RoHS, the pin-compatible MAX9763EUI+ (the lead-free suffix variant) is the drop-in replacement — same package, same output stage, same thermal pad.