Diodes new Tiny Audio Class-D Amp Produces 1.9 W from 5V

June 2 2015, 04:00
The PAM8905 is a new audio amp chip from Diodes Incorporated measuring just 1.5 x 2.0 mm. The design operates in Class-D mode, achieving a total harmonic distortion of 1% (plus noise) and delivering a maximum of 1.9 W into 8 ohm using a power supply in the range between 2.8 V to 5.2 V.

Aimed at smartphones and mobile applications operating from a single-cell lithium-ion battery, the PAM8905 is also designed for audio systems that need to deliver a high sound pressure level (SPL) output from a low supply voltage. It maximizes the output power of the amplifier compared to a standard amplifier connected directly to the battery.

The new PAM8905 features an integrated boost converter powering the output stage to achieve the rated output power and maintaining perceived volume with falling battery voltage. The boost converter is a fully synchronous design, ensuring a low external component count and high efficiency.

According to Diodes, the built-in boost converter generates the voltage rail for the output stage. This provides a louder audio output than a stand-alone amplifier connected directly to the battery. It also maintains a consistent loudness, regardless of battery voltage. The PAM8905 also features 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.

Protection features of the PAM8905 include DC input protection which safeguards the speakers when the input is biased at a high DC voltage, output short circuit protection with auto recovery, under-voltage lockout, over-temperature and ON/OFF pop noise suppressor.

The PAM8905 is available in a tiny 12-lead WCSP12 package measuring just 1.5 x 2.0 mm, helping to save PCB space. Applications for the new audio device include smartphones, GPS systems and any portable electronics and low-power speakers.
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