Aimed at smartphones operating from a single-cell lithium-ion battery, the PAM8905 from Diodes Inc. is a 1.9W class-D audio amplifier designed for audio systems that need to deliver a high sound pressure level (SPL) output from a low supply voltage. It achieves this with a built-in boost converter that generates the voltage rail for the output stage while using a battery-tracking automatic gain control (AGC) to adjust the gain and limit battery current when the battery voltage is low, thus prolonging battery life.

With its high-efficiency class-D audio power amplifier and integrated boost converter, the PAM8905 drives up to 1.9W into an 8W speaker with a total harmonic distortion plus noise (THD+N) of just 1%. The fully synchronous topology of the boost circuit minimizes external components, achieves higher efficiency and maximizes the output power of the amplifier compared to a standard amplifier connected directly to the battery. The built-in AGC function ensures excellent sound reproduction and further helps extend battery lifetime.

The PAM8905 features DC input voltage protection to prevent damage to the speaker in the event of input voltages with high DC bias levels. The device is also protected against output short circuits with full auto-recovery and has under-voltage lockout (UVLO) and over-temperature protection. Supplied in a 12-pin U-WLB1520-12 CSP package measuring just 15mm x 20mm x 0.6mm, the PAM8905 provides a low pin-count and small size solution to save board space.