It’s easy to damage small speakers in portable devices and monitors when they are used to produce loud sounds or bass frequencies. The voice coil temperature can rise quickly at high volume levels, causing the glue to melt, and large excursions of the speaker membrane due to strong bass signals can strain or break the speaker. Conventional solutions rely on large safety margins to prevent speaker damage, but even then the speaker may exceed its limits or the amplifier may clip the drive signal. Both situations impair sound quality and result in sound that is far below the true capability of the speaker.
The TFA9887 and TFA9890 audio drivers from NXP let speakers reach their full potential. Featuring an integrated DC/DC converter to boost maximum output power and an embedded DSP to shape the audio signal, they monitor speaker behavior in real time by measuring the voice coil temperature and speaker excursion, and they detect potential signal clipping. A sophisticated speaker protection algorithm in the DSP optimizes the audio signal. Direct control of speaker excursion enables improved bass reproduction. It also protects the speaker if the enclosure becomes leaky or the speaker port is blocked,yielding better sound quality and longer lifetime.
The TFA9887 class-D amplifier can deliver 2.65 W RMS to an 8-ohm speaker, while the newer TFA9890 can deliver 3.4 W RMS with a 3.6 V supply voltage.